宽输入电压范围正变负控制器LTC3704
ltc2954的用法
ltc2954的用法摘要：1.简介2.特性3.应用领域4.使用方法4.1 接线4.2 配置4.3 操作5.常见问题及解决方案6.总结正文：【简介】LTC2954 是德州仪器（Texas Instruments）公司生产的一款高精度、低漂移的电压基准芯片，具有4 路输出，广泛应用于各种电子设备中，提供精确稳定的电压参考。
【特性】LTC2954 具有以下特性：1.4 路输出，输出电压分别为2.5V、1.25V、0.625V 和0.313V；2.低漂移，典型值为±2ppm/°C；3.高精度，典型值为±0.02%；4.低噪声，典型值为1μVp-p；5.宽工作电压范围，1.8V 至5.5V；6.紧凑型5 引脚SC70 封装。
【应用领域】LTC2954 电压基准芯片广泛应用于通信、工业控制、医疗设备、仪器仪表等领域，为这些设备提供精确稳定的电压参考。
【使用方法】【接线】使用时，将LTC2954 的VCC 引脚连接到1.8V 至5.5V 电源，GND 引脚连接到地，然后将输出引脚连接到需要提供电压参考的电路。
【配置】LTC2954 无需外部元件即可工作，但在某些应用场景下，可以通过外接电阻调整输出电压。
例如，通过连接一个电阻到OUT1 引脚，可以调整OUT1 的输出电压。
【操作】LTC2954 在接通电源后即可正常工作，无需额外的操作。
但在实际应用中，建议对电路进行适当的设计和布局，以降低噪声和干扰。
【常见问题及解决方案】1.输出电压不准确：可能是由于电源电压波动或负载电流变化导致的，可以通过使用稳压电源和使用合适的负载电阻来解决；2.温度漂移较大：可能是由于环境温度变化或电路布局不合理导致的，可以通过改善电路散热条件或使用散热片来解决。
【总结】LTC2954 是一款性能优异的电压基准芯片，具有高精度、低漂移、低噪声等优点，广泛应用于各种电子设备中。
CN3701_02_03_04应用电路图
5A锂电池充电管理集成电路CN3701/CN3702/CN3703/CN3704应用电路图1、简介CN3701/CN3702/CN3703/CN3704是可以对1-4节锂离子电池或锂聚合物电池进行恒流/恒压充电的充电器电路。
该芯片是PWM降压模式锂电池充电管理集成电路，独立对锂电池充电进行全面自动管理，具有封装外形小，外围元器件少和使用简单等优点，非常适合便携式应用领域。
2、特点●宽输入电压范围：7.5V 到 28V●锂电池完整的充电管理●充电电流达5A●PWM开关频率：300KHz●恒压充电电压精度：±1%●恒流充电电流由外部电阻设置●对深度放电的电池进行涓流充电●充电结束电流可由外部电阻设置●电池温度监测功能●自动再充电功能●充电状态和充电结束状态指示●软启动功能●电池端过压保护●工作环境温度：－40℃ 到 ＋85℃●采用16管脚TSSOP封装●产品无铅，无卤素元素，满足RoHS3、应用●便携式DVD,对讲机●笔记本电脑●备用电池应用●便携式工业和医疗仪器●独立电池充电器典型应用电路1使用温度监控功能，充电显示和充电结束显示。
输入电源VCC50V10uF50V10uF3.3K 3.3K①输入电源VCC的选择：CN3701>7.5V，CN3702>11.5V，CN3703>14.5V，CN3704>19V，但是输入电源VCC不能超过28V。
②电容的选择：输入输出电容可根据具体电路的纹波系数选择，如果电路的纹波比较大，应当选择一个大一点的电容，纹波比较小，选择一个比较小的电容，一般情况下选择50V10uF即可，电解电容为宜；C2，C3，C4，C5都为陶瓷电容，选择应用电路图中的数值即可。
③PMOS管M1的选择：一般情况下当充电电流小于2.5A时，选择AO3407A；当充电电流为2.5A—5A时，选择SI4435DY。
④肖特基二极管D1和D2的选择：一般情况下当充电电流小于2.5A时，选择30BQ015；当充电电流为2.5A—5A时，选择50WQ03FN。
优秀的双晶正激DC-DC控制器LTC3705-3706
优秀的双晶正激DC/DC控制IC.LTC3705/LTC3706在通讯48V输入电压的DC/DC变换器中，双晶正激电路也能完成很好的电压转换，这是不少工程师常忽略的问题，双晶正激磁芯自动无损复位，对效率的提升也很重要，它的变压器也不必象有源箝位一样地去加入谐振参数，做好二次侧同步整流即可达到高效率。
凌特公司的LTC3705及LTC3706即专门为此设计。
两颗IC的技朮特色●LTC3705具有内部隔离的高低端MOSFET驱动能力。
●片内整流器可自起动，可省去辅助绕组驱动。
●宽的输入工作电压范围，可以从18V～80V输入，瞬间可达100V。
●线性Vcc供电达到快速起动。
●精密欠压锁定的UVLO，且阈什窗口可调。
●过流保护。
●伏秒积限制，防止变压器饱合。
●电压前馈，提高瞬态应变能力。
●LTC3706作二次侧控制具有快速瞬态响应能力。
●片内自起动电路，不要另加偏置源。
●恰如其分的同步整流栅驱动，减少系统的复杂程度。
●可实现二次侧过流保护及多相均流。
●工作电压从5V～30V。
下面细致分析由LTC3705和LTC3706组成48V/3.3V 20A的DC/DC设计。
引脚功能说明先介绍LTC3705，然后是LTC3706。
GND 1PIN信号地。
I S2PIN过流比较器的输入端，接至电流检测电阻正端。
此电阻串入低端MOSFET的源极到GND之间。
V SLMT3PIN伏秒积限制，形成一个RC网，从V IN接到V SLMT，再到GND，当V SLMT电压超过1.25V时，关断栅驱动。
UVLO 4PIN欠压锁定，接一电阻分压器从V IN到GND，分压端子接入UVLO，当V UVLO ＞1.242V时，IC工作，窗口为16mV,有49μA窗口电流以改变窗口阈值，为电压前馈检测V IN，可用作外部ON/OFF控制。
SSFLT 5PIN结合软起动及故障指示器，此处接一电容到地，设置占空比斜波的斜率，指示故障，故障时其升至Vcc的1.3V以内。
LTC3707中文资料
13707fbTF EATURESA PPLICATIONS DESCRIPTION Synchronous Step-DownSwitching RegulatorThe L TC ®3707 is a high performance dual step-down switching regulator controller that drives N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows adjustment of the frequency up to 300kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The precision 0.8V reference and power good output indicator are compatible with future microprocessor generations, and a wide 3.5V to 30V input supply range encompasses all battery chemistries.A RUN/SS pin for each controller provides both soft-start and optional timed, short-circuit shutdown. Current foldback limits MOSFET dissipation during short-circuit conditions when overcurrent latchoff is disabled. Output overvoltage protection circuitry latches on the bottom MOSFET until V OUT returns to normal. The FCB mode pin can select among B urst Mode operation, constant frequency mode and continuous inductor current mode or regulate a secondary winding.Figure 1. High Effi ciency Dual 5V/3.3V Step-Down Converter■180° Phased Dual Controllers Reduce Required Input Capacitance and Power Supply Induced Noise ■ OPTI-LOOP ® Compensation Minimizes C OUT■ ±1.5% Output Voltage Accuracy over Temperature ■ Dual N-Channel MOSFET Synchronous Drive ■ Power Good Output Voltage Monitor■ DC Programmed Fixed Frequency 150kHz to 300kHz ■ Wide V IN Range: 4.5V to 28V Operation■ Very Low Dropout Operation: 99% Duty Cycle ■ Adjustable Soft-Start Current Ramping ■ Foldback Output Current Limiting■ Latched Short-Circuit Shutdown with Defeat Option ■ Output Overvoltage Protection ■ Remote Output Voltage Sense ■ Low Shutdown I Q: 20μA ■ 5V and 3.3V Standby Regulators■ Selectable Constant Frequency, Burst Mode ® Operation or PWM Operation■ Small 28-Lead Narrow SSOP Package■Notebook and Palmtop Computers, PDAs ■ B attery Chargers ■ Portable Instruments■ Battery-Operated Digital Devices ■ DC Power Distribution SystemsL , L T , L TC, L TM, Burst Mode, and OPTI-LOOP are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5705919, 5929620, 6144194, 6177787, 6304066, 6580258.V OUT2LTC370723707fbP IN CONFIGURATIONA BSOLUTE MAXIMUM RATINGS Input Supply Voltage (V IN ) .........................30V to –0.3V Top Side Driver Voltages(BOOST1, BOOST2) ...................................36V to –0.3V Switch Voltage (SW1, SW2) .........................30V to –5V INTV CC, EXTV CC , RUN/SS1, RUN/SS2, (BOOST1-SW1), (BOOST2-SW2), PGOOD ..............................7V to –0.3V SENSE1+, SENSE2+, SENSE1–,SENSE2– Voltages.........................(1.1)INTV CC to –0.3V FREQSET , STBYMD, FCB Voltage .........INTV CC to –0.3V I TH1, I TH2, V OSENSE1, V OSENSE2 Voltages ...2.7V to –0.3V Peak Output Current <10μs (TG1, TG2, BG1, BG2) .....3A INTV CC Peak Output Current ................................. 40mA Operating Temperature Range (Note 2)....–40°C to 85°C Junction Temperature (Note 3) .............................125°C Storage Temperature Range ...................–65°C to 150°C Lead Temperature (Soldering, 10 sec) ..................300°C(Note 1)SYMBOL PARAMETERCONDITIONSMIN TYP MAX UNITS V OSENSE1, 2Regulated Feedback Voltage (Note 4); I TH1, 2 Voltage = 1.2V l0.7880.8000.812V I OSENSE1, 2Feedback Current(Note 4)–5–50nA V REFLNREG Reference Voltage Line Regulation V IN = 3.6V to 30V (Note 4)0.0020.02%/V V LOADREGOutput Voltage Load Regulation(Note 4)Measured in Servo Loop; ΔI TH Voltage = 1.2V to 0.7V Measured in Servo Loop; ΔI TH Voltage = 1.2V to 2.0V l l 0.1–0.10.5–0.5%%g m1,2T ransconductance Amplifi er g mI TH1, 2 = 1.2V; Sink/Source 5μA; (Note 4)1.3mmhoORDER INFORMATIONLEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE L TC3707EGN#PBF L TC3707EGN#TRPBF 3707EGN 28-Lead Plastic SSOP –40°C to 85°C L TC3707IGN#PBF L TC3707IGN#TRPBF 3707IGN 28-Lead Plastic SSOP –40°C to 85°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE L TC3707EGN L TC3707EGN#TR 3707EGN 28-Lead Plastic SSOP –40°C to 85°C L TC3707IGNL TC3707IGN#TR3707IGN28-Lead Plastic SSOP–40°C to 85°CConsult L TC Marketing for parts specifi ed with wider operating temperature ranges.For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear .com/tapeandreel/ELECTRICAL CHARACTERISTICSThe l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T A = 25°C. V IN = 15V , V RUN/SS1, 2 = 5V unless otherwise noted.LTC370733707fbE LECTRICAL CHARACTERISTICS SYMBOL PARAMETERCONDITIONS MIN TYP MAX UNITSg mGBW1, 2T ransconductance Amplifi er GBW I TH1, 2 = 1.2V; (Note 4)3MHz I QInput DC Supply CurrentNormal Mode Standby Shutdown(Note 5)EXTV CC Tied to V OUT1 = 5V V RUN/SS1, 2 = 0V , V STBYMD > 2V V RUN.SS1, 2 = 0V , V STBYMD = Open3501252035μA μA μA V FCB Forced Continuous Threshold l0.760.8000.84V I FCB Forced Continuous Pin Current V FCB = 0.85V –0.30–0.18–0.1μA V BINHIBIT Burst Inhibit (Constant Frequency) ThresholdMeasured at FCB pin 4.34.8V UVLO Undervoltage Lockout V IN Ramping Down l 3.54V V OVL Feedback Overvoltage Lockout Measured at V OSENSE1, 2l0.840.860.88V I SENSE Sense Pins Total Source Current (Each Channel); V SENSE1–, 2– = V SENSE1+, 2+ = 0V –90–60μA V STBYMD MS Master Shutdown Threshold V STBYMD Ramping Down0.40.6VV STBYMD KA Keep-Alive Power On-Threshold V STBYMD Ramping Up, RUN SS1, 2 = 0V 1.52V DF MAX Maximum Duty Factor In Dropout 9899.4%I RUN/SS1, 2Soft-Start Charge Current V RUN/SS1, 2 = 1.9V 0.5 1.2μAV RUN/SS1, 2 ON RUN/SS Pin ON ThresholdV RUN/SS1, V RUN/SS2, Rising 1.01.52.0V V RUN/SS1, 2 L T RUN/SS Pin Latchoff Arming ThresholdV RUN/SS1, V RUN/SS2, Rising from 3V 4.14.75V I SCL1, 2RUN/SS Discharge Current Soft Short Condition V OSENSE1, 2 = 0.5V; V RUN/SS1, 2 = 4.5V 0.524μA I SDLHO Shutdown Latch Disable Current V OSENSE1, 2 = 0.5V1.65μA V SENSE(MAX)Maximum Current Sense Threshold V OSENSE1, 2 = 0.7V , V OSENSE1–, 2– = 5V l 656275758588mV mV TG1, 2 t r TG1, 2 t f TG T ransition Time:Rise Time Fall Time (Note 6)C LOAD = 3300pF C LOAD = 3300pF 6060110110ns ns BG1, 2 t r BG1, 2 t f BG T ransition Time:Rise Time Fall Time(Note 6)C LOAD = 3300pF C LOAD = 3300pF5050110100ns ns TG/BG t 1D Top Gate Off to Bottom Gate On Delay Synchronous Switch-On Delay Time C LOAD = 3300pF Each Driver 80ns BG/TG t 2D Bottom Gate Off to Top Gate On Delay Top Switch-On Delay Time C LOAD = 3300pF Each Driver 80ns t ON(MIN)Minimum On-Time Tested with a Square Wave (Note 7)180nsINTV CC Linear RegulatorV INTVCC Internal V CC Voltage 6V < V IN < 30V , V EXTCC = 4V 4.85.0 5.2V V LDO INT INTV CC Load Regulation I CC = 0 to 20mA, V EXTVCC = 4V 0.2 2.0%V LDO EXT EXTV CC Voltage Drop I CC = 20mA, V EXTVCC = 5V100200mV V EXTVCC EXTV CC Switchover Voltage I CC = 20mA, EXTV CC Ramping Positivel 4.54.7V V LDOHYS EXTV CC Hysteresis 0.2VOscillator f OSC Oscillator Frequency V FREQSET = Open (Note 8)190220250kHz f LOWLowest FrequencyV FREQSET = 0V120140160kHzThe l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T A= 25°C. V IN= 15V , V RUN/SS1, 2= 5V unless otherwise noted.LTC370743707fbEffi ciency vs Output Current (Figure 13)Effi ciency vs Input Voltage (Figure 13)SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS f HIGH Highest Frequency V FREQSET = 2.4V 280310360kHz I FREQSET FREQSET Input Current V FREQSET = 0V –2–1μA 3.3V Linear RegulatorV 3.3OUT 3.3V Regulator Output Voltage No Load l3.203.35 3.45V V 3.3IL 3.3V Regulator Load Regulation I 3.3 = 0 to 10mA 0.52%V 3.3VL3.3V Regulator Line Regulation 6V < V IN < 30V 0.050.2%PGOOD Output V PGL PGOOD Voltage Low I PGOOD = 2mA 0.10.3V I PGOOD PGOOD Leakage CurrentV PGOOD = 5V1μA V PGPGOOD T rip Level, Either ControllerV OSENSE Respect to Set Output VoltageV OSENSE Ramping Negative V OSENSE Ramping Positive–6 6–7.5 7.5–9.5 9.5%%Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime.Note 2: The L TC3707E is guaranteed to meet performance specifi cations from 0°C to 85°C. Specifi cations over the –40°C to 85°C operatingtemperature range are assured by design, characterization and correlation with statistical process controls. The L TC3707I is guaranteed to meet performance specifi cations over the full –40°C to 85°C operating temperature range.Note 3: T J is calculated from the ambient temperature T A and power dissipation P D according to the following formula: L TC3707EGN = T J = T A + (P D • 85°C/W)Note 4: The L TC3707 is tested in a feedback loop that servos V ITH1, 2 to a specifi ed voltage and measures the resultant V OSENSE1, 2.Note 5: Dynamic supply current is higher due to the gate charge being delivered at the switching frequency. See Applications Information.Note 6: Rise and fall times are measured using 10% and 90% levels. Delay times are measured using 50% levels.Note 7: The IC minimum on-time is tested under an ideal conditionwithout external power FETs. It can be different when the IC is working in an actual circuit. See Minimum On-Time Considerations in the Application Information section.Note 8: V FREQSET pin internally tied to a 1.19V reference through a large resistance.TYPICAL PERFORMANCE CHARACTERISTICSEffi ciency vs Output Current and Mode (Figure 13)OUTPUT CURRENT (A)0.0010E F F I C I E N C Y (%)10304050100700.010.113707 G012080906010OUTPUT CURRENT (A)0.001E F F I C I E N C Y (%)7080103707 G0260500.010.1110090INPUT VOL TAGE (V)5E F F I C I E N C Y (%)70803707 G036050152530100V OUT = 5V I OUT = 3A90 E LECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T A= 25°C. V IN= 15V , VRUN/SS1, 2= 5V unless otherwise noted.LTC370753707fbTYPICAL PERFORMANCE CHARACTERISTICSSupply Current vs Input Voltage and Mode (Figure 13)EXTV CC Voltage DropINTV CC and EXTV CC Switch Voltage vs TemperatureInternal 5V LDO Line RegMaximum Current Sense Threshold vs Duty FactorMaximum Current SenseThreshold vs Percent of Nominal Output Voltage (Foldback)Maximum Current SenseThreshold vs V RUN/SS (Soft-Start)Maximum Current Sense Threshold vs Sense Common Mode VoltageCurrent Sense Threshold vs I TH VoltageINPUT VOL TAGE (V)50S U P P L Y C U R R E N T (μA )40010001020253707 G042008006001530CURRENT (mA)0E X T V C C V O L T A G E D R O P (m V )20015010050403707 G05102030TEMPERATURE (°C)–50I N T V C C A N D E X T V C C S W I T C H V O L T A G E (V )4.955.005.0525753707 G064.904.85–25501001254.804.704.75INPUT VOLTAGE (V)04.84.95.115253707 G074.74.651020304.54.45.0I N T V C C V O L T A G E(V )DUTY FACTOR (%)0V S E N S E (m V )255075204060803707 G08100PERCENT ON NOMINAL OUTPUT VOLTAGE (%)0V S E N S E (m V )4050601003707 G0930200255075108070V RUN/SS (V)00V S E N S E (m V )2040608012343707 G1056COMMON MODE VOLTAGE (V)V S E N S E (m V )72768043707 G116864601235V ITH (V)0V S E N S E (m V )3050709023707 G1210–10204060800–20–300.511.52.5LTC370763707fbTYPICAL PERFORMANCE CHARACTERISTICSLoad RegulationV ITH VS V RUN/SSSENSE Pins Total Source CurrentMaximum Current Sense Threshold vs TemperatureDropout Voltage vs Output Current (Figure 13)RUN/SS Current vs TemperatureSoft-Start Up (Figure 13)Load Step (Figure 13)Load Step (Figure 13)LOAD CURRENT (A)0N O R M A L I Z E D V O U T (%)–0.2–0.143707 G13–0.3–0.412350.0V RUN/SS (V)V I T H (V )0.51.01.52.02.512343707 G1456V SENSE COMMON MODE VOLTAGE (V)0I S E N S E (μA )3707 G15–50–10024501006TEMPERATURE (°C)–50–2570V S E N S E (m V )7480050753707 G1772787625100125OUTPUT CURRENT (A)00D R O P O U T V O L T A GE (V )12340.51.0 1.52.03707 G182.53.0 3.54.0TEMPERATURE (°C)–50–250R U N /S S C U R R E N T (μA )0.20.60.81.075100501.83707 G250.40251251.21.41.6V IN = 15V VOUT = 5V5ms/DIV3707 G19V RUN/SS 5V/DIVV OUT 5V/DIV I OUT 2A/DIVV IN = 15VVOUT = 5VLOAD STEP = 0A TO 3A Burst Mode OPERATION20μs/DIV 3707 G20V OUT 200mV/DIVI OUT 2A/DIV V IN = 15VV OUT = 5VLOAD STEP = 0A TO 3A CONTINUOUS OPERATION20μs/DIV 3707 G21V OUT 200mV/DIVI OUT 2A/DIVLTC370773707fbTYPICAL PERFORMANCE CHARACTERISTICSInput Source/CapacitorInstantaneous Current (Figure 13)Burst Mode Operation (Figure 13)Constant Frequency (Burst Inhibit) Operation (Figure 13)Current Sense Pin Input Current vs TemperatureEXTV CC Switch Resistance vs TemperatureOscillator Frequency vs TemperatureUndervoltage Lockout vs TemperatureShutdown Latch Thresholds vs TemperatureTEMPERATURE (°C)–50–2525C U R R E N T S E N S E I N P U T C U R R E N T (μA )2935050753707 G2627333125100125TEMPERATURE (°C)–50–250E X T V C C S W I T C H R E S I S T A N C E (Ω)410050753707 G2728625100125TEMPERATURE (°C)–5020025035025753707 G28150100–255010012550300F R E Q U E N C Y (k H z )TEMPERATURE (°C)–50U N D E R V O L T A G E L O C K O U T (V )3.403.453.5025753707 G293.353.30–25501001253.253.20TEMPERATURE (°C)–50–250S H U T D O W N L A T C H T H R E S H O L D S (V )0.51.52.02.575100504.53707 G301.00251253.03.54.0V IN = 15VV OUT = 5VI OUT5 = I OUT3.3 = 2A1μs/DIV 3707 G22V IN200mV/DIV IIN 2A/DIV V SW210V/DIVV SW110V/DIVV IN = 15V V OUT = 5V V FCB = OPEN I OUT = 20mA10μs/DIV3707 G23I OUT 0.5A/DIVV OUT 20mV/DIVV IN = 15V V OUT = 5V V FCB = 5V I OUT = 20mA2μs/DIV3707 G24I OUT 0.5A/DIVV OUT 20mV/DIVLTC370783707fbP IN FUNCTIONS RUN/SS1, RUN/SS2 (Pins 1, 15): Combination of soft-start, run control inputs and short-circuit detection timers. A capacitor to ground at each of these pins sets the ramp time to full output current. Forcing either of these pins back below 1.0V causes the IC to shut down the circuitry required for that particular controller . Latchoff overcurrent protection is also invoked via this pin as described in the Applications Information section.SENSE1+, SENSE2+ (Pins 2, 14): The (+) Input to the Differential Current Comparators. The I TH pin voltage and controlled offsets between the SENSE – and SENSE + pins in conjunction with R SENSE set the current trip threshold.SENSE1–, SENSE2– (Pins 3, 13): The (–) Input to the Differential Current Comparators.V OSENSE1, V OSENSE2 (Pins 4, 12): Receives the remotely-sensed feedback voltage for each controller from an external resistive divider across the output.FREQSET (Pin 5): Frequency Control Input to the Oscillator . This pin can be left open, tied to ground, tied to INTV CC or driven by an external voltage source. This pin can also be used with an external phase detector to build a true phase-locked loop.STBYMD (Pin 6): Control pin that determines which cir-cuitry remains active when the controllers are shut down and/or provides a common control point to shut down both controllers. See the Operation section for details.FCB (Pin 7): Forced Continuous Control Input. This input acts on both controllers and is normally used to regulate a secondary winding. Pulling this pin below 0.8V will force continuous synchronous operation on both controllers. Do not leave this pin fl oating.I TH1, I TH2 (Pins 8, 11): Error Amplifi er Output and Switching Regulator Compensation Point. Each associated channels’ current comparator trip point increases with this control voltage.SGND (Pin 9): Small Signal Ground common to both controllers, must be routed separately from high current grounds to the common (–) terminals of the C OUT capacitors.3.3V OUT (Pin 10): Output of a linear regulator capable of supplying 10mA DC with peak currents as high as 50mA.PGND (Pin 20): Driver Power Ground. Connects to the sources of bottom (synchronous) N-channel MOSFETs, anodes of the Schottky rectifi ers and the (–) terminal(s) of C IN .INTV CC (Pin 21): Output of the Internal 5V Linear Low Dropout Regulator and the EXTV CC Switch. The driver and control circuits are powered from this voltage source. Must be decoupled to power ground with a minimum of 4.7μF tantalum or other low ESR capacitor . The INTV CC regulator standby function is determined by the STBYMD pin.EXTV CC (Pin 22): External Power Input to an Internal Switch Connected to INTV CC . This switch closes and supplies V CC power , bypassing the internal low dropout regulator , when-ever EXTV CC is higher than 4.7V . See EXTV CC connection in Applications section. Do not exceed 7V on this pin.BG1, BG2 (Pins 23, 19): High Current Gate Drives for Bot-tom (Synchronous) N-Channel MOSFETs. Voltage swing at these pins is from ground to INTV CC .V IN (Pin 24): Main Supply Pin. A bypass capacitor should be tied between this pin and the signal ground pin.BOOST1, BOOST2 (Pins 25, 18): Bootstrapped Supplies to the Top Side Floating Drivers. Capacitors are connected between the boost and switch pins and Schottky diodes are tied between the boost and INTV CC pins. Voltage swing at the boost pins is from INTV CC to (V IN + INTV CC ).SW1, SW2 (Pins 26, 17): Switch Node Connections to Inductors. Voltage swing at these pins is from a Schottky diode (external) voltage drop below ground to V IN .TG1, TG2 (Pins 27, 16): High Current Gate Drives for Top N-Channel MOSFETs. These are the outputs of fl oat-ing drivers with a voltage swing equal to INTV CC – 0.5V superimposed on the switch node voltage SW .PGOOD (Pin 28): Open-Drain Logic Output. PGOOD is pulled to ground when the voltage on either V OSENSE pin is not within ±7.5% of its set point.LTC370793707fbFUNCTIONAL DIAGRAMOUTFigure 2LTC3707103707fbO PERATION Main Control LoopThe L TC3707 uses a constant frequency, current mode step-down architecture with the two controller channels operating 180 degrees out of phase. During normal operation, each top MOSFET is turned on when the clock for that channel sets the RS latch, and turned off when the main current comparator , I 1, resets the RS latch. The peak inductor current at which I 1 resets the RS latch is controlled by the voltage on the I TH pin, which is the output of each error amplifi er EA. The V OSENSE pin receives the voltage feedback signal, which is compared to the internal reference voltage by the EA. When the load current increases, it causes a slight decrease in V OSENSE relative to the 0.8V reference, which in turn causes the I TH voltage to increase until the average inductor current matches the new load current. After the top MOSFET has turned off, the bottom MOSFET is turned on until either the inductor current starts to reverse, as indicated by current comparator I 2, or the beginning of the next cycle.The top MOSFET drivers are biased from fl oating bootstrap capacitor C B , which normally is recharged during each off cycle through an external diode when the top MOSFET turns off. As V IN decreases to a voltage close to V OUT , the loop may enter dropout and attempt to turn on the top MOSFET continuously. The dropout detector detects this and forces the top MOSFET off for about 500ns every tenth cycle to allow C B to recharge.The main control loop is shut down by pulling the RUN/SS pin low. Releasing RUN/SS allows an internal 1.2μA current source to charge soft-start capacitor C SS . When C SS reaches 1.5V , the main control loop is enabled with the I TH voltage clamped at approximately 30% of its maximum value. As C SS continues to charge, the I TH pin voltage is gradually released allowing normal, full-current operation. When both RUN/SS1 and RUN/SS2 are low, all L TC3707 controller functions are shut down, and the STBYMD pin determines if the standby 5V and 3.3V regulators are kept alive.Low Current OperationThe FCB pin is a multifunction pin providing two functions: 1) an analog input to provide regulation for asecondary winding by temporarily forcing continuous PWM operation on both controllers and 2) a logic input to select between two modes of low current operation. When the FCB pin voltage is below 0.800V , the controller forces continuous PWM current mode operation. In this mode, the top and bottom MOSFETs are alternately turned on to maintain the output voltage independent of direction of inductor current. When the FCB pin is below V INTVCC – 2V but greater than 0.80V , the controller enters Burst Mode operation. Burst Mode operation sets a minimum output current level before inhibiting the top switch and turns off the synchronous MOSFET(s) when the inductor current goes negative. This combination of requirements will, at low currents, force the I TH pin below a voltage threshold that will temporarily inhibit turn-on of both output MOSFETs until the output voltage drops. There is 60mV of hysteresis in the burst comparator B tied to the I TH pin. This hysteresis produces output signals to the MOSFETs that turn them on for several cycles, followed by a variable “sleep” interval depending upon the load current. The resultant output voltage ripple is held to a very small value by having the hysteretic comparator after the error amplifi er gain block.Constant Frequency OperationWhen the FCB pin is tied to INTV CC , Burst Mode operation is disabled and the forced minimum output current requirement is removed. This provides constant frequency, discontinuous (preventing reverse inductor current) current operation over the widest possible output current range. This constant frequency operation is not as effi cient as Burst Mode operation, but does provide a lower noise, constant frequency operating mode down to approximately 1% of designed maximum output current. Voltage should not be applied to the FCB pin prior to the application of voltage to the V IN pin.Continuous Current (PWM) OperationTying the FCB pin to ground will force continuous current operation. This is the least effi cient operating mode, but may be desirable in certain applications. The output can source or sink current in this mode. When sinking current while in forced continuous operation, current will(Refer to Functional Diagram)OPERATIONbe forced back into the main power supply potentially boosting the input supply to dangerous voltage levels—BEWARE!Frequency SettingThe FREQSET pin provides frequency adjustment of the internal oscillator from approximately 140kHz to 310kHz. This input is nominally biased through an internal resistor to the 1.19V reference, setting the oscillator frequency to approximately 220kHz. This pin can be driven from an ex-ternal AC or DC signal source to control the instantaneous frequency of the oscillator. Voltage should not be applied to the FREQSET pin prior to the application of voltage to the V IN pin.INTV CC/EXTV CC PowerPower for the top and bottom MOSFET drivers and most other internal circuitry is derived from the INTV CC pin. When the EXTV CC pin is left open, an internal 5V low dropout linear regulator supplies INTV CC power. If EXTV CC is taken above 4.7V, the 5V regulator is turned off and an internal switch is turned on connecting EXTV CC to INTV CC. This allows the INTV CC power to be derived from a high effi ciency external source such as the output of the regulator itself or a secondary winding, as described in the Applications Information.Standby Mode PinThe STBYMD pin is a three-state input that controls com-mon circuitry within the IC as follows: When the STBYMD pin is held at ground, both controller RUN/SS pins are pulled to ground providing a single control pin to shut down both controllers. When the pin is left open, the internal RUN/SS currents are enabled to charge the RUN/SS capacitor(s), allowing the turn-on of either controller and activating necessary common internal biasing. When the STBYMD pin is taken above 2V, both internal linear regulators are turned on independent of the state on the RUN/SS pins of the two switching regulator controllers, providing an output power source for “wake-up” circuitry. Decouple the pin with a small capacitor (0.01μF) to ground if the pin is not connected to a DC potential. Output Overvoltage ProtectionAn overvoltage comparator, 0V, guards against transient overshoots (>7.5%) as well as other more serious condi-tions that may overvoltage the output. In this case, the top MOSFET is turned off and the bottom MOSFET is turned on until the overvoltage condition is cleared.Power Good (PGOOD) PinThe PGOOD pin is connected to an open drain of an in-ternal MOSFET. The MOSFET turns on and pulls the pin low when both the outputs are not within ±7.5% of their nominal output levels as determined by their resistive feedback dividers. When both outputs meet the ±7.5% requirement, the MOSFET is turned off within 10μs and the pin is allowed to be pulled up by an external resistor to a source of up to 7V.Foldback Current, Short-Circuit Detectionand Short-Circuit LatchoffThe RUN/SS capacitors are used initially to limit the inrush current of each switching regulator. After the controller has been started and been given adequate time to charge up the output capacitors and provide full load current, the RUN/SS capacitor is used in a short-circuit time-out circuit. If the output voltage falls to less than 70% of its nominal output voltage, the RUN/SS capacitor begins discharging on the assumption that the output is in an overcurrent and/or short-circuit condition. If the condition lasts for a long enough period as determined by the size of the RUN/SS capacitor, the controllers will be shut down until the RUN/SS pin(s) voltage(s) are recycled. This built-in latchoff can be overridden by providing a >5μA pull-up at a compliance of 4.2V to the RUN/SS pin(s). This current shortens the soft start period but also prevents net dis-charge of the RUN/SS capacitor(s) during an overcurrent and/or short-circuit condition. Foldback current limiting is also activated when the output voltage falls below 70% of its nominal level whether or not the short-circuit latchoff circuit is enabled. Even if a short is present and the short-circuit latchoff is not enabled, a safe, low output current is provided due to internal current foldback and actual power dissipated is low due to the effi cient nature of the current mode switching regulator.(Refer to Functional Diagram)。
LTC3708EUH-TRPBF资料
13708fbT YPICAL APPLICATIONF EATURESA PPLICATIONS DESCRIPTION Buck Controller withOutput TrackingnDigital Signal Processors n Network ServersL , L T , L TC and L TM are registered trademarks of Linear Technology Corporation. No R SENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.High Effi ciency Dual Output Step-Down ConverternVery Low Duty Factor Operation (t ON(MIN) < 85ns)n No R SENSE ™ Option for Maximum Effi ciency n Very Fast T ransient Responsen Programmable Output Voltage Up/Down T racking n 2-Phase Operation Reduces Input Capacitance n 0.6V ±1% Output Voltage Reference n External Frequency Synchronization n Monotonic Soft-Startn Onboard High Current MOSFET Drivers n Wide V IN Range: Up to 36Vn Adjustable Cycle-by-Cycle Current Limit n Instant Output Overvoltage Protection n Optional Short-Circuit Shutdown Timer n Power Good Output with 100μs Masking n Available in 5mm × 5mm QFN PackageThe L TC ®3708 is a dual, 2-phase synchronous step-down switching regulator with output voltage up/down tracking capability. The IC allows either coincident or ratiometric tracking. Multiple L TC3708s can be daisy-chained in ap-plications requiring more than two voltages to be tracked. Power supply sequencing is accomplished using an external soft-start timing capacitor .The L TC3708 uses a constant on-time, valley current mode control architecture to deliver very low duty factors without requiring a sense resistor . Operating frequency is selected by an external resistor and is compensated for variations in input supply voltage. An internal phase-locked loop allows the IC to be synchronized to an external clock.Fault protection is provided by an output overvoltage comparator and an optional short-circuit shutdown timer . The regulator current limit level is user programmable. A wide supply range allows voltages as high as 36V to be stepped down to 0.6V output.VOUT2V OUT2(0.5V/DIV)V OUT1(0.5V/DIV)LOAD CURRENT (A)80E F F I C I E N C Y (%)POWER LOSS (W)901007585950.011103708 TA01c70 4.57.59.03.01.56.000.123708fbP IN CONFIGURATIONA BSOLUTE MAXIMUM RATINGS (Note 1)32313029282726259101112TOP VIEW33UH PACKAGE32-LEAD (5mm s 5mm) PLASTIC QFN13141516171819202122232487654321RUN/SS I TH1V FB1TRACK1SGND TRACK2V FB2I TH2SENSE1–PGND1BG1DRV CC BG2PGND2SENSE2–V CCV R N G 1F C BP G O O DI O N 1B O O S T 1T G 1S W 1S E N S E 1+E X T L P FI N T L P FV R N G 2I O N 2B O O S T 2T G 2S W 2S E N S E 2+T JMAX = 125°C, θJA = 34°C/WEXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCBORDER INFORMATIONLEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTIONTEMPERATURE RANGE L TC3708EUH#PBF L TC3708EUH#TRPBF 370832-Lead (5mm × 5mm) Plastic QFN –40°C to 85°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTIONTEMPERATURE RANGE L TC3708EUHL TC3708EUH#TR370832-Lead (5mm × 5mm) Plastic QFN–40°C to 85°CConsult L TC Marketing for parts specifi ed with wider operating temperature ranges.For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear .com/tapeandreel/Input Supply Voltage (V CC , DRV CC ) ............. 7V to –0.3V Boosted Topside Driver Supply VoltageBOOST1, 2 ............................................ 42V to –0.3V Switch Voltage (SW1, 2) .............................. 36V to –5V SENSE1+, SENSE2+ Voltages ....................... 36V to –5V SENSE1–, SENSE2– Voltages .................... 10V to –0.3V I ON1, I ON2 Voltages .................................... 21V to –0.3V (BOOST – SW) Voltages ..............................7V to –0.3V RUN/SS, PGOOD Voltages .......................... 7V to –0.3V PGOOD DC Current ................................................. 5mA TRACK1, TRACK2 Voltages ..............V CC + 0.3V to –0.3VV RNG1, V RNG2 Voltages.................... V CC + 0.3V to –0.3V I TH1, I TH2 Voltages.................................... 2.7V to –0.3V V FB1, V FB2 Voltages .................................. 2.7V to –0.3V INTLPF , EXTLPF Voltages ......................... 2.7V to –0.3V FCB Voltages ............................................... 7V to –0.3V Operating Temperature Range (Note 5)....–40°C to 85°C Junction Temperature (Note 2) ........................... 125°C Storage Temperature Range ...................–65°C to 125°C Refl ow Peak Body Temperature ........................... 260°CE LECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operatingtemperature range, otherwise specifi cations are at T A = 25°C. V CC = 5V , DRV CC = 5V , unless otherwise noted.SYMBOL PARAMETERCONDITIONS MIN TYP MAX UNITSMain Control LoopI QInput DC Supply CurrentNormal Shutdown2.42503400mA μA I FB1,2Feedback Pin Input Current I TH = 1.2V (Notes 3, 4)–50–100nA V REF Internal Reference Voltage I TH = 1.2V , 0°C to 85°C (Notes 3, 4)I TH = 1.2V (Notes 3, 4)l0.5940.5910.6000.6000.6060.609V V V FB1,2Feedback VoltageI TH = 1.2V (Note 3)0.5940.6000.606V ΔV FB(LINEREG)1,2Feedback Voltage Line RegulationV CC = 4.5V to 6.5V (Note 3)0.02%/VE LECTRICAL CHARACTERISTICSThel denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T A = 25°C. V CC = 5V, DRV CC = 5V, unless otherwise noted.SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS ΔV FB(LOADREG)1,2Feedback Voltage Load Regulation I TH = 0.5V to 1.9V (Note 3)–0.05–0.2% g m(EA)1,2Error Amplifi er T ransconductance I TH = 1.2V (Note 3)l 1.2 1.45 1.7mSt ON1,2On-Time I ON = 60μA, V FCB = 0VI ON = 30μA, V FCB = 0V 94186116233138280nsnst ON(MIN)1,2Minimum On-Time I ON = 180μA5085ns t OFF(MIN)1,2Minimum Off-Time I ON = 30μA270350nsV SENSE(MAX)1,2Maximum Current Sense Threshold V RNG = 1V, V FB = 0.565VV RNG = 0V, V FB = 0.565VV RNG = VCC, V FB = 0.565V 12590180143100200160110220mVmVmVV SENSE(MIN)1,2Minimum Current Sense Threshold V RNG = 1V, V FB = 0.635VV RNG = 0V, V FB = 0.635VV RNG = V CC, V FB = 0.635V –62–42–88mVmVmVΔV FB(OV)1,2Overvoltage Fault Threshold8.51011.5%ΔV FB(UV)1,2Undervoltage Fault Threshold–380–420–460mV V RUN/SS(ON)RUN Pin Start Threshold l0.8 1.3 1.8V V RUN/SS(LE)RUN Pin Latchoff Enable Threshold RUN/SS Pin Rising 2.63 3.3V V RUN/SS(L T)RUN Pin Latchoff Threshold RUN/SS Pin Falling 2.2 2.5 2.8V I RUN/SS(C)Soft-Start Charge Current V RUN/SS = 0V–0.5–1.2–2μA I RUN/SS(D)Soft-Start Discharge Current V RUN/SS = V RUN/SS(LE), V FB1,2 = 0V0.823μA V CC(UVLO)Undervoltage Lockout V CC Falling 3.2 3.6V V CC(UVLOR)Undervoltage Lockout Release V CC Rising 3.5 3.8V TG R UP1,2TG Driver Pull-Up On-Resistance TG High (Note 6)2ΩTG R DOWN1,2TG Driver Pull-Down On-Resistance TG Low (Note 6)2ΩBG R UP1,2BG Driver Pull-Up On-Resistance BG High (Note 6)3ΩBG R DOWN1,2BG Driver Pull-Down On-Resistance BG Low (Note 6)1ΩT rackingI TRACK1,2TRACK Pin Input Current I TH = 1.2V, V TRACK = 0.2V (Note 3)–100–150nAV FB(TRACK1,2)Feedback Voltage at T racking V TRACK = 0V, I TH = 1.2V (Note 3)V TRACK = 0.2V, I TH = 1.2V (Note 3)V TRACK = 0.4V, I TH = 1.2V (Note 3)–10190390200400–10210410mVmVmVPGOOD OutputΔV FBH1,2PGOOD Upper Threshold Either V FB Rising8.51011.5%ΔV FBL1,2PGOOD Lower Threshold Either V FB Falling–8.5–10–11.5%ΔV FB(HYS)1,2PGOOD Hysteresis V FB Returning35% V PGL PGOOD Low Voltage I PGOOD = 5mA0.10.4V I PGOOD PGOOD Leakage Current V PGOOD = 7V±1μA PG Delay PGOOD Delay V FB Falling100μs Phase-Locked LoopsV FCB(DC)Forced Continuous Threshold Measured with a DC Voltage at FCB Pin 1.9 2.1 2.3V V FCB(AC)Clock Input Threshold Measured with a AC Pulse at FCB Pin1 1.52V I EXTLPF External Phase Detector Output CurrentSourcing Capability Sinking Capability f FCB < f SW1, V EXTLPF = 0Vf FCB > f SW1, V EXTLPF = 2.420–20μAμA33708fb43708fbT YPICAL PERFORMANCE CHARACTERISTICS Load T ransient on Channel 1Load T ransient on Channel 2Coincident T rackingRatiometric T rackingE LECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operatingtemperature range, otherwise specifi cations are at T A = 25°C. V CC = 5V , DRV CC = 5V , unless otherwise noted.SYMBOL PARAMETERCONDITIONSMINTYP MAXUNITS I INTLPFInternal Phase Detector Output CurrentSourcing Capability Sinking Capabilityf SW1 < f SW2, V INTLPF = 0V f SW1 > f SW2, V INTLPF = 2.4 20–20μA μA t ON(PLL)1t ON1 Modulation Range by External PLL Up Modulation Down ModulationI ON1 = 60μA, V EXTLPF = 1.8V I ON1 = 60μA, V EXTLPF = 0.6V 1862335880ns ns t ON(PLL)2t ON2 Modulation Range by Internal PLL Up Modulation Down ModulationI ON1 = 60μA, V EXTLPF = 1.8V I ON1 = 60μA, V EXTLPF = 0.6V1862335880ns nsNote 1:Stresses beyond those listed under Absolute Maximum Ratingsmay cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliabilty and lifetime.Note 2: T J is calculated from the ambient temperature T A and power dissipation PD as follows:T J = T A + (P D• 34°C/W)Note 3: The L TC3708 is tested in a feedback loop that adjusts V FB to achieve a specifi ed error amplifi er output voltage (I TH ).Note 4: Internal reference voltage is tested indirectly by extracting erroramplifi er offset from the feedback voltage.Note 5: The L TC3708E is guaranteed to meet performance specifi cations from 0°C to 85°C. Specifi cations over the –40°C to 85°C operatingtemperature range are assured by design, characterization and correlation with statistical process controls.Note 6: R DS(ON) limit is guaranteed by design and/or correlation to static test.I OUT110A/DIVV OUT1100mV/DIV20μs/DIV3708 G01V OUT2100mV/DIVV OUT10.5V/DIV V OUT20.5V/DIV2ms/DIV3708 G03V OUT10.5V/DIV V OUT20.5V/DIV2ms/DIV3708 G0453708fbTYPICAL PERFORMANCE CHARACTERISTICSSoft-StartPower Loss vs Input VoltagePower Loss vs Load CurrentFrequency vs Input VoltageFrequency vs Load CurrentOn-Time vs I ON CurrentOn-Time vs TemperatureCurrent Sense Threshold vs I TH VoltageV OUT12V/DIV V OUT22V/DIV RUN/SS 5V/DIVI L15A/DIV50ms/DIV3708 G05INPUT VOL TAGE (V)50P O W E R L O S S (W )123456101520253708 G06LOAD (mA)102.02.53.5100003707 G071.51.010010001000000.503.0P O W E R L O S S (W )INPUT VOL TAGE (V)5F R E Q U E N C Y (k H z )200220253708 G08180160101520260240LOAD CURRENT (A)F R E Q U E N C Y (k H z )1001503708 G095051015250200I ON CURRENT (μA)110O N -T I M E (n s )1001000100001010010003708 G10TEMPERATURE (°C)–500O N -T I M E (n s )501001502000501001503708 G11250300–252575125I TH VOLTAGE (V)0C U R R E N T S E N S E T H R E S H O L D (m V )10020030023708 G120–10050150250–50–150–2000.511.52.563708fbT YPICAL PERFORMANCE CHARACTERISTICS Maximum Current SenseThreshold vs V RNG VoltageMaximum Current Sense Threshold vs TemperatureLoad Regulation (Figure 13 Circuit)Error Amplifi er g m vs TemperatureSENSE Pin Input Current vs TemperatureRUN/SS Pin Current vs TemperatureFeedback Voltage vs RUN/SS (Soft-Start)RUN/SS Latch-Off Thresholds vs TemperatureUndervoltage Lockout Threshold vs TemperatureV RNG VOLTAGE (V)0.5350300250200150100500 1.25 1.753708 G130.7511.52M A X I M U M C U R R E N T S E N S E T H R E S H O L D (m V)TEMPERATURE (°C)–50M A X I M U M C U R R E N T S E N S E T H R E S H O L D (m V )14015016025751503708 G14130120110–2550100125LOAD CURRENT (A)0–0.2–0.10123708 G15–0.3–0.436915–0.5–0.6–0.7$V O U T (%)TEMPERATURE (°C)–501.0g m (m S )1.11.21.31.40501001503708 G161.51.6–252575125TEMPERATURE (°C)–5050I S E N S E (μA )608090100150120050753708 G1770130140110–2525100125150TEMPERATURE (°C)–50–25–2R U N /S S P I N C U R R E N T (μA )3050753708 G18–12125100125RUN/SS VOLTAGE (V)170060050040030020010001.752.253708 G191.251.52 2.5V F B(m V )TEMPERATURE (°C)–502.0R U N /S S T H R E S H O L D (V )2.53.03.54.0–2525503708 G2075100125150TEMPERATURE (°C)–50U N D E R V O L T A G E L O C K O U T T H R E S H O L D (V )3.54.04.525751503708 G213.02.52.0–255010012573708fbTYPICAL PERFORMANCE CHARACTERISTICSOn-Time vs EXTLPF VoltageOn-Time vs INTLPF Voltage2-Phase OperationEXTLPF VOLTAGE (V)10t O N 1 (n s )50150200250500350 1.1 1.23708 G22100400450300 1.31.4INTLPF VOLTAGE (V)0.60t O N 2 (n s )501502002505003501 1.4 1.63708 G231004004503000.81.2 1.82.0I IN 2A/DIV V SW110V/DIVV SW210V/DIVV IN200mV/DIV 1μs/DIV V IN = 15V V OUT1 = 5V V OUT2 = 3.3VI OUT5= I OUT3 = 2A3708 G024I OUT110A/DIVSW110V/DIV10μs/DIV3708 G25V OUT150mV/DIVf S = 200kHzf S = 240kHzLoad T ransient Response with External SynchronizationI OUT110A/DIVSW110V/DIV 10μs/DIV3708 G26V OUT150mV/DIVf S = 220kHzf S= 220kHzDiscontinuous Mode OperationPower Good MaskI L0.5A/DIVV OUT 20mV/DIV2μs/DIVV IN = 15V V OUT = 5V V FCB = 5V I OUT = 20mA3708 G027V FB 0.2V/DIV100μs/DIV3708 G28PGOOD 2V/DIVP IN FUNCTIONSRUN/SS (Pin 1): Run Control and Soft-Start Input. A capacitor to ground at this pin sets the ramp rate of the output voltage (approximately 0.5s/μF) and the time delay for overcurrent latchoff (see Applications Information). Forcing this pin below 0.8V shuts down the L TC3708.I TH1, I TH2 (Pins 2, 8): Error Amplifi er Compensation Point and Current Control Threshold. The current comparator threshold increases with this control voltage. The voltage ranges from 0V to 2.4V with 0.8V corresponding to zero sense voltage (zero current).V FB1, V FB2 (Pins 3, 7): Error Amplifi er Feedback Input. This pin connects the error amplifi er input to an external resistive divider from V OUT . Additional compensation can be implemented, if desired, using this pin.TRACK1, TRACK2 (Pins 4, 6): Tie TRACK2 pin to a re-sistive divider connected to the output of channel 1 for either coincident or ratiometric output tracking. TRACK1 is used in the same manner between multiple L TC3708s (see Applications Information). To disable this feature, tie the pins to V CC. Do Not Float These Pins.SGND (Pins 5, 33): Signal Ground. All small-signal com-ponents and compensation components should connect to this ground and eventually connect to PGND at one point. The Exposed Pad of the L TC3708EUH must be soldered to the PCB.EXTL PF (Pin 9): Filter Connection for the External PLL. This PLL is used to synchronize the L TC3708 to an external clock. If external clock is not used, leave this pin fl oating. INTLPF (Pin 10): Filter Connection for the Internal PLL. This PLL is used to phase shift the second channel to the fi rst channel by 180°.V CC (Pin 17): Main Input Supply. Decouple this pin to SGND with an RC fi lter (10Ω, 1μF for example).DRV CC (Pin 21): Driver Supply. Provides supply to the drivers for the bottom gates. Also used for charging the bootstrap capacitors.BG1, BG2 (Pins 22, 20): Bottom Gate Drive. Drives the gate of the bottom N-channel MOSFET between ground and DRV CC.PGND1, PGND2 (Pins 23, 19): Power Ground. Connect this pin closely to the source of the bottom N-channel MOSFET, the (–) terminal of C DRVCC and the (–) terminal of C IN. SENSE1–, SENSE2– (Pins 24, 18): Current Sense Com-parator Input. The (–) input to the current comparator is used to accurately Kelvin sense the bottom side of the sense resistor or MOSFET.SENSE1+, SENSE2+ (Pins 25, 16): Current Sense Com-parator Input. The (+) input to the current comparator is normally connected to the SW node unless using a sense resistor (See Applications Information).SW1, S W2 (Pins 26, 15):S witch N ode. T he (–) t erminal o f t he bootstrap capacitor C B connects here. This pin swings from a Schottky diode voltage drop below ground up to V IN. TG1, TG2 (Pins 27, 14): Top Gate Drive. Drives the top N-channel MOSFET with a voltage swing equal to DRV CC superimposed on the switch node voltage SW. BOOST1, BOOST2 (Pins 28, 13): Boosted Floating Driver Supply. The (+) terminal of the bootstrap capacitor C B connects here. This pin swings from a diode voltage drop below DRV CC up to V IN + DRV CC.I ON1, I ON2 (Pins 29, 12): On-Time Current Input. Tie a resistor from V IN to this pin to set the one-shot timer current and thereby set the switching frequency. PGOOD (Pin 30): Power Good Output. Open-drain logic output that is pulled to ground when either or both output voltages are not within ±10% of the regulation point. The output voltage must be out of regulation for at least 100μs before the power good output is pulled to ground.FCB (Pin 31): Forced Continuous and External Clock Input. Tie this pin to ground to force continuous synchronous operation or to V CC to enable discontinuous mode opera-tion at light load. Feeding an external clock signal into this pin will synchronize the L TC3708 to the external clock and enable forced continuous mode.V RNG1, V RNG2 (Pins 32, 11): Sense Voltage Range Input. The voltage at this pin is ten times the nominal sense volt-age at maximum output current and can be programmed from 0.5V to 2V. The sense voltage defaults to 70mV when this pin is tied to ground, 140mV when tied to V CC.83708fbFUNCTIONAL DIAGRAMOUTREF93708fbO PERATION(Refer to Functional Diagram)Main Control LoopThe L TC3708 uses a constant on-time, current mode step-down architecture with two control channels operating at 180 degrees out of phase. In normal operation, each top MOSFET is turned on for a fi xed interval determined by its own one-shot timer OST. When the top MOSFET is turned off, the bottom MOSFET is turned on until the current comparator I CMP trips, restarting the one-shot timer and repeating the cycle. The trip level of the current comparator is set by the I TH voltage which is the output of each error amplifi er, EA. Inductor current is determined by sensing the voltage between the SENSE– and SENSE+ pins using either the bottom MOSFET on-resistance or a separate sense resistor. At low load currents, the inductor current can drop to zero and become negative. This is detected by current reversal comparator I REV, which then shuts off M2 resulting in discontinuous operation. Both switches will remain off with the output capacitor supplying the load current until the I TH voltage rises above the zero current level (0.8V) to initiate another cycle. Discontinuous mode operation is disabled when the FCB pin is brought below 1.9V, forcing continuous synchronous operation.The main control loop is shut down by pulling the RUN/SS pin low, turning off both M1 and M2. Releasing the pin al-lows an internal 1.2μA current source to charge an external soft-start capacitor, C SS. When this voltage reaches 1.3V, the controller turns on and begins switching, but with the effective reference voltage clamped at 0V. As C SS continues to charge, the effective reference ramps up at the same rate and controls the rise rate of the output voltage. Operating FrequencyThe operating frequency is determined implicitly by the top MOSFET on-time and the duty cycle required to maintain regulation. The one-shot timer generates an on-time that is proportional to the ideal duty cycle, thus holding frequency approximately constant with changes in V IN. The nominal frequency can be adjusted with an external resistor R ON. When the L TC3708 is synchronized to an external clock, the operating frequency will then be solely determined by the external clock.Output Overvoltage ProtectionAn overvoltage comparator OV guards against transient overshoots (>10%) as well as other more serious condi-tions that may overvoltage the output. In this condition, M1 is turned off and M2 is turned on and held on until the condition is cleared.Short-Circuit Detection and ProtectionAfter the controller has been started and given adequate time to charge the output capacitors, the RUN/SS capacitor is used as the short-circuit time-out capacitor. If either one of the output voltages falls to less than 70% of its nominal output voltage, the RUN/SS capacitor begins discharging on the assumption that the output is in an overcurrent and/or short-circuit condition. If the condition lasts for a long enough period, as determined by the size of the RUN/SS capacitor, both controllers will be shut down until the RUN/SS pin voltage is recycled. This built-in latchoff can be overridden by providing >5μA pull-up at a compli-ance of 5V to the RUN/SS pin. This current shortens the soft-start period but also prevents net discharge of the RUN/SS capacitor during an overcurrent and/or short-circuit condition.Power Good (PGOOD) PinOvervoltage and undervoltage comparators OV and UV pull the PGOOD output low if the output feedback volt-age exceeds a ±10% window around the regulation point. In addition, the output feedback voltage must be out of this window for a continuous duration of at least 100μs before PGOOD is pulled low. This is to prevent any glitch on the feedback voltage from creating a false power bad signal. The PGOOD will indicate high immediately when the feedback voltage is in regulation.103708fbO PERATION (Refer to Functional Diagram)DRV CCPower for the top and bottom MOSFET drivers is derived from the DRV CC pin. The top MOSFET driver is powered from a fl oating bootstrap capacitor , C B . This capacitor is normally recharged from DRV CC through an external Schottky diode, D B , when the top MOSFET is turned off.2-Phase OperationFor the L TC3708 to operate optimally as a 2-phase controller , the resistors connected to the I ON pins must be selected such that the free-running frequency of each channel is close to that of the other . An internal phase-locked loop (PLL) will then ensure that channel 2 operates at the same frequency as channel 1, but phase shifted by 180°. The loop fi lter connected to the INTLPF pin provides stability to the PLL. For external clock synchronization, a second PLL is incorporated to adjust the on-time of channel 1 until its frequency is the same as the external clock. Compensation for the external PLL is through the EXTLPF pin.The loop fi lter components tied to the INTLPF and EXTLPF pins are used to compensate the internal PPL and external PLL respectively. The typical value ranges are:INTLPF: R IPLL = 2kΩ to 10kΩ, C IPLL = 10nF to 100nF EXTLPF: R EPLL ≤ 1kΩ, C EPLL = 10nF to 100nF For noise suppression, a capacitor with a value of 1nF or less should be placed from INTLPF to ground and EXTLPF to ground.The L TC3708’s 2-phase operation brings considerable benefi ts to portable applications and automatic electron-ics. It lowers the input fi ltering requirement, reduces electromagnetic interference (EMI) and increases the power conversion effi ciency. Until the introduction of the 2-phase operation, dual switching regulators operated both channels in phase (i.e., single phase operation). This means that both controlling switches turned on at the same time, causing current pulses of up to twice the amplitude of those for one regulator to be drawn from the input capacitor or battery. Such operation results in higher input RMS current, larger and/or more expensive input capacitors, more power loss and worse EMI in the input source (whether a wall adapter or a battery).In contrast to single phase operation, the two channels of a 2-phase switching regulator are operated 180 degrees out of phase. This effectively interleaves the current pulses drawn by the switches, greatly reducing the overlap time where they add together . The result is a signifi cant reduc-tion in total RMS input current, which in turn allows less expensive input capacitors to be used, reduces shielding requirements for EMI and improves real world operating effi ciency.Figure 1 compares the input waveforms for a representative single phase dual switching regulator to the 2-phase dual switching regulator . An actual measurement of the RMS input current under these conditions shows that 2-phase dropped the input current from 2.53A RMS to 1.55A RMS .Figure 1. Input Waveforms Comparing Single Phase (1a) and 2-Phase (1b) Operationfor Dual Switching Regulators Converting 12V to 5V and 3.3V at 3A Each5V SWITCH 20V/DIV 3.3V SWITCH 20V/DIV INPUT CURRENT5A/DIV INPUT VOL TAGE 500mV/DIVI IN(MEAS) = 2.53A RMS I IN(MEAS) = 1.55A RMS(1a)(1b)3708 F01O PERATION(Refer to Functional Diagram)While this is an impressive reduction in itself, remember that the power losses are proportional to I2RMS, meaning that the actual power wasted is reduced by a factor of 2.66. The reduced input ripple current also means that less power is lost in the input power path, which could include batteries, switches, trace/connector resistances and protection circuitry. Improvements in both conducted and radiated EMI also directly accrue as a result of the reduced RMS input current and voltage.Of course, the improvement afforded by 2-phase opera-tion is a function of the dual switching regulator’s relative duty cycles which, in turn, are dependent upon the input voltage, V IN. Figure 2 shows how the RMS input current varies for single phase and 2-phase operation for 3.3V and5V regulators over a wide input voltage range.It can readily be seen that the advantages of 2-phase opera-tion are not just limited to a narrow operating range, but inINPUT VOLTAGE (V)INPUTRMSCURRENT(A)3.02.52.01.51.00.5102030403708 F02Figure 2. RMS Input Current Comparisonfact extend over a wide region. A good rule of thumb for most applications is that 2-phase operation will reduce the input capacitance requirement to that for just one channel operating at maximum current and 50% duty cycle.A PPLICATIONS INFORMATIONThe basic L TC3708 application circuit is shown on the fi rst page of this data sheet. External component selection is primarily determined by the maximum load current and begins with the selection of the power MOSFET switches and/or sense resistor. For the L TC3708, the inductor cur-rent is determined by the R DS(ON) of the synchronous MOSFET or by a sense resistor when the user opts for more accurate current sensing. The desired amount of ripple current and operating frequency largely determines the inductor value. Finally, C IN is selected for its ability to handle the large RMS current into the converter and C OUT is chosen with low enough ESR to meet the output voltage ripple specifi cation.Maximum Sense Voltage and V RNG PinInductor current is determined by measuring the voltage across the R DS(ON) of the synchronous MOSFET or through a sense resistor that appears between the SENSE+ and SENSE– pins. The maximum sense voltage is set by the voltage applied to the V RNG pin and is equal to approximately V RNG/7. The current mode control loop will not allow the inductor current valleys to exceed V RNG/(7 • R SENSE). In practice, one should allow some margin for variations in the L TC3708 and external component values. A good guide for selecting the sense resistance is:R V ISENSERNGOUT MAX =10•()The voltage of the V RNG pin can be set using an external resistive divider from V CC between 0.5V and 2V, resulting in nominal sense voltages of 50mV to 200mV. Additionally, the V RNG pin can be tied to ground or V CC, in which case the nominal sense voltage defaults to 70mV or 140mV, respectively. The maximum allowed sense voltage is about 1.4 times this nominal value.Connecting the SENSE+ and SENSE– PinsThe L TC3708 provides the user with an optional method to sense current through a sense resistor instead of using the R DS(ON) of the synchronous MOSFET. When using a sense resistor, it is placed between the source of the syn-chronous MOSFET and ground. To measure the voltage across this resistor, connect the SENSE+ pin to the source of the synchronous MOSFET and the SENSE– pin to the other end of the resistor. The SENSE+ and SENSE– pins provide the Kelvin connections, ensuring accurate voltage measurement across the resistor. Using a sense resistor provides a well-defi ned current limit, but adds cost and reduces effi ciency. Alternatively, one can use the synchro-nous MOSFET as the current sense element by simply connecting the SENSE+ pin to the switch node SW and the SENSE– pin to the source of the synchronous MOSFET, eliminating the sense resistor. This improves effi ciency, but one must carefully choose the MOSFET on-resistance as discussed below.Power MOSFET SelectionEach output stage of the L TC3708 requires two external N-channel power MOSFETs, one for the top (main) switch and one for the bottom (synchronous) switch. Important parameters for the power MOSFETs are the breakdown voltage V(BR)DSS, threshold voltage V GS(TH), on-resistance R DS(ON), reverse transfer capacitance, C RSS, and maximum current, I DS(MAX).The gate drive voltage is set by the 5V DRV CC supply. Consequently, logic-level threshold MOSFETs must be used in L TC3708 applications. If the driver’s voltage is expected to drop below 5V, then sub-logic level threshold MOSFETs should be considered.When the bottom MOSFET is used as the current sense element, particular attention must be paid to its on-re-sistance. MOSFET on-resistance is typically specifi ed with a maximum value R DS(ON)(MAX) at 25°C. Additional margin is required to accommodate the rise in MOSFET on-resistance with temperature:RRDS ON MAXSENSET()()=ρThe ρT term is a normalization factor (unity at 25°C) ac-counting for the signifi cant variation in on-resistance with temperature, typically about 0.4%/°C. For a maximum junction temperature of 100°C, using a value ρ100°C = 1.3 is reasonable (see Figure 3).。
宽输入电压范围升压 - 负输出 - SEPIC 控制器
宽输入电压范围升压/ 负输出/ SEPIC 控制器引言当今的许多电子设备都需要一个负输出或正输出转换器，有时则是两者均需要。
另外，它们还必需采用各种电源运作，包括USB、墙上适配器、碱性电池和锂电池等。
为了从可变输入电压产生不同极性的输出，电源设计师常常采用多种稳压器IC，因而导致库存元器件品种的增加。
LT®3759 可在 1.6V 至42V 的输入电压范围内工作，并采用同一个反馈引脚来控制正输出或负输出，从而缩减了库存清单并简化了设计。
该器件还将许多受欢迎的功能(例如：软起动、可调频率和同步) 整合在小巧的占板面积之内。
LT3759 采用5mm x 4mm 12 引脚MSE 封装，并可在多种配置中使用，例如：升压、SEPIC、反激式和Cuk 拓扑结构。
宽输入电压范围和内部LDOLT3759 的宽输入范围简化了那些必须与众多输入电源相兼容的电源设计。
由于LT3759 包含两个分别由VIN 和DRIVE 引脚供电的内部低压差(LDO) 电压稳压器，因此无需增设外部稳压器或采用一种缓慢充电迟滞起动方案，从而实现了简单的启动和偏置。
LT3759 的内部INTVCC 电流限制功能电路可防止IC 产生过大的片内功率耗散。
输出电压的检测变得容易LT3759 采用了一种新颖的FBX 引脚架构，该架构可简化负输出和正输出转换器的设计。
它包含两个内部误差放大器(一个检测正输出，而另一个则检测负输出)，并允许FBX 引脚从一个正输出或负输出直接连接至分压器，从而消除了与正输出或负输出检测有关的任何困惑，并简化了电路板布局。
您只需确定输出极性和拓扑结构，其余的工作都可交给LT3759 完成。
LT3758 - 高输入电压、升压、反激式、SEPIC 和负输出控制器
LT3758 - 高输入电压、升压、反激式、SEPIC 和负输
出控制器
描述
LT®3758是一款宽输入电压范围、电流模式、DC/DC 控制器，该器件能够产生正输出或负输出电压。
它可以被配置为一个升压、反激式、SEPIC 或负输出转换器。
LT3758 从一个内部7.2V 稳压电源来驱动一个低端外部N 沟道功率MOSFET。
固定频率、电流模式架构在一个很宽的电源电压和输出电压范围内实现了稳定的操作。
LT3758 的工作频率可利用一个外部电阻器来设定(可设置范围为100kHz 至1MHz)，并能够采用SYNC 引脚来使其同步至一个外部时钟。
由于具有一个 5.5V 的最小工作电源电压和一个低停机静态电流(1μA)，因而使LT3758 成为电池供电式系统的理想选择。
LT3758 具有软起动和频率折返功能，用于在启动和输出短路期间限制电感器电流。
特点
·宽输入电压范围：5.5V 至100V
·利用单个反馈引脚来设置正或负输出电压
·电流模式控制提供超卓的瞬态响应
·可利用一个外部电阻器来设置工作频率(100kHz 至1MHz)
·可同步至一个外部时钟
·低停机电流：1μA
·内部7.2V 低压差稳压器
·具迟滞的可编程输入欠压闭锁。
uc3842改可调电源教程_《学习笔记》--DCDC电源电路设计实例
图1 基于LTC3704的电源电路原理图图2 TLC3704电源电路电路流向1）如图1所⽰，通过控制LTC3074开关控制开关管Q1的通断，以形成输出电压；3）如图1中的②，电源输⼊端由3.3V供电，输⼊端的滤波电路由电感（L3）、磁珠（E1）与电容构成，作⽤是滤除3.3V电源平⾯上的作⽤是滤除3.3V电源平⾯上的纹波和噪声，以免对电源电路构成⼲扰；4）如图1中的③，四个滤波电容中，C4应最靠近引脚，其次是C3和C2，C1应布放在最外边，其作⽤是滤除由LTC3704产⽣的对3.3V电源平⾯的⼲扰；4、元器件的选型1）输出电压的设置。
NFB引脚⽤于对输出电压的设置，输出端的分压反馈经NFB引脚输⼊到电源芯⽚内部，经反向后接到⽐较器的⼀端，通过调整MOSFET的占空⽐，增⼤输出电压。
2）MOSFET占空⽐的计算：3）选择电源芯⽚的⼯作模式MODE引脚⽤于设置芯⽚的⼯作模式，包括：突发模式和连续模式。
突发模式：适⽤于负载较轻负载较轻的场合；重负载场合。
连续模式：适⽤于重负载4）⼯作频率的确定通过FREQ引脚于GND之间连接电阻的阻值，可对电源芯⽚的开关频率进⾏配置。
5）电感的选型流过电感的电流是波动的，所以需要确定设计所允许的波动范图1中L1是承载输⼊电流，⽽L2是承载输出电流，在DC/DC电源电路中，流过电感的电流是波动围。
电感值越⼩，则电流波动越⼤，⽽电电流波动过⼩，不利于电流检测环路的建⽴；电感值越⼩电流波动于电感有关，电感值越⼤，则电流波动越⼩（电流波动过⼩不适合⼯作于连续模式）。
流波动过⼤，则电路不适合⼯作于连续模式输⼊电流：输⼊电感（L1）和输出电感（L2）的峰值电流：合流的总峰值电流：电感：6）确定电流感应电阻的阻值原理都是利⽤电阻将流过MOSFET的转变为电压，并与内部的参考电平⽐较。
利⽤Q1的导通电阻，SENCE引脚与Q1的漏极相连，在Q1的栅极与GND之间⽆需添加电阻；利⽤Q1的栅极和GND之间的电阻。
LT3704 中文数据手册 datasheet
LQWYFF 3hP^_`h LQWYFF 3hP`hIF
LQWYFF 3hP`hIF
LQWYFF <ZIF LQWYFF 3hPh@ tWUl1OsSCV LQWYFF `@`.
pqh?F
pn
,>DyP^_2HV1
pc
,>DyP^_1@V1
H3 UIUHT A >6h
cRVF A 966hKu .P</ YV\QF A 6Y P ;Y YV\QF A 6Y P ;Y
NDNCM > ;3XZRIKBC2OTJA > 3RZ;h6B_]\
Ny
@>
.MF
cRVF
RZPc@
RZPc43;V_44oc@V
pV\QF.PLQ/ PRGH5V\QF _7^.hF4r
pV\QF.PD[/ PRGH5V\QF _4^.hF4r
YLO.PRGH/
Y`s PRGH5V\QF ^.`h
YLK.PRGH/
s`s PRGH5V\QF ^.`h
UPRGH5V\QF PRGH5V\QF ^.1H`d
YIUHT
IUHT OI<v`h
AT|`TF
YLQWYFF qYLQWYFF
qYLQ7 qYLQWYFF
qYLQ8 YOGR.ORDG/
YGURSRXW
LLQWYFF
YUXQ1 YUXQx
_7^.`h
^.`h`@`. U@SC 6uSCUXps<Z tWSC
UXQ ^.`h2HTc?
UXQ ^.`h1@Tc?
YUXQ.K\VW/ LUXQ YQIE
UXQ OI^.c?`p UXQ ^.`. <JP`h
宽压输入隔离稳压正、负双输出系列产品数据手册说明书
ZY_WHAD-3W宽压输入隔离稳压正、负双输出系列——————————————概述ZY_WHAD-3W 系列电源模块是一种宽压输入隔离稳压正、负双输出电源模块，其转换效率高，高低温度特性好，带容性负载能力强，具有短路保护等功能，可持续短路，自恢复。
国际标准引脚方式，UL94-VO 阻燃封装，自然冷却，无需外加散热片，无需外加元件可直接使用，并可直接焊在PCB 板上。
电路结构为闭环自动控制系统，具有电压精度高等优点。
连接简单，是您前级电源的理想解决方案。
——————————————产品特性◆ 转换效率高达80%；◆ 输入电压：+9-36V ，+18-72V ； ◆ 双端稳压输出；◆ 输出精度：典型值±1%； ◆ 可持续短路，自恢复；◆ 外壳材料符合UL94-V0标准； ◆ 工作温度：-40℃～+85℃； ◆ 开关频率：80-550(PFM)； ◆隔离电压：1500VDC 。
————————————产品应用● 计算机外围设备； ● 工业控制系统； ● 数据通讯设备；● 分步式电源控制系统； ● 模拟/数字系统； ●……—————————————订购信息————————————————————————————————原理框图图 1 原理框图如图 1所示为该系列电源模块的原理框图。
该电路采用PFM 电路，内部具有反馈电路，输出精度高达±1%。
特别适用于输入电压变化范围大而且输入输出必须隔离的电路，如工业控制系统电源，数据通讯系统，分步式电源控制系统等。
广州致远电子股份有限公司修订历史目录1. 引脚信息 (1)1.1ZY_WHAD-3W引脚信息 (1)2. ZY_WHAD-3W产品选型 (2)3. ZY_WHAD-3W特性参数 (3)3.1参数列表 (3)3.2绝缘特性 (3)4. 机械尺寸 (4)5. 电路连接 (5)6. 免责声明 (6)1. 引脚信息1.1 ZY_WHAD-3W 引脚信息● 产品实物图图 1.1 ZY_WHAD-3W 实物图产品尺寸：长（L ）*宽（W ）*高（H ），31.8*20.3*9.5mm 。
基于LTC3780的四开关升降压型汽车开关电源设计
LTC1144资料
2
U
W
U
U
W W
W
元器件交易网
LTC1144 TYPICAL PERFORMANCE CHARACTERISTICS
Output Resistance vs Supply Voltage
元器件交易网
LTC1144 Switched-Capacitor Wide Input Range Voltage Converter with Shutdown
FEATURES
s s s s s s
DESCRIPTIO
s s
Wide Operating Supply Voltage Range: 2V to 18V Boost Pin (Pin 1) for Higher Switching Frequency Simple Conversion of 15V to –15V Supply Low Output Resistance: 120Ω Maximum Power Shutdown to 8µA with SHDN Pin Open Circuit Voltage Conversion Efficiency: 99.9% Typical Power Conversion Efficiency: 93% Typical Easy to Use
ORDER PART NUMBER LTC1144CN8 LTC1144IN8
N8 PACKAGE 8-LEAD PLASTIC DIP T JMAX = 110°C, θJA = 100°C/W
TOP VIEW BOOST 1 CAP+ 2 GND 3 CAP– 4 8 7 6 5 V+ OSC SHDN VOUT
LTC1144CS8 LTC1144IS8 S8 PART MARKING 1144 1144I
LTC4365 LTC4365-1过压、欠压、反向供电保护控制器示例电路手册说明书
DescriptionOvervoltage, Undervoltage and Reverse Supply Protection ControllerDemonstration circuit DC1555C is intended to demon-strate the performance of the LTC4365 and LTC4365-1 Undervoltage, Overvoltage and Reverse Supply Protection Controllers.The L TC®4365/LTC4365-1 protect circuits from input volt-ages that may be too high, too low or negative. It operates by controlling the gates of two back-to-back connected MOSFETs to keep the output in a safe range. The OV and UV protection levels are adjusted by resistive dividers at the OV and UV pins. Asserting the SHDN pin disables the MOSFETs and places the controller in a low-current shut-down state. The FAUL T pin is asserted when the Controlleris in shutdown mode or when the input voltage is outside of the UV or OV level.The LTC4365 and LTC4365-1 can withstand DC voltages between –40V and +60V and have a valid operating range of 2.5V to 34V.L, L T, L TC, L TM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.performance summary(T A = 25°C)Regarding the supply protection parameters, the LTC4365 and LTC4365-1 are identical. The only differences are in the gate fault recovery delay time and the delay from turn-off to low-power operation. These delays are 36ms (typ, both) for the LTC4365, while they are 1ms and 0.7ms respectively for the LTC4365-1.The DC1555C includes the controller, two back-to-back connected power MOSFETs, three jumpers and three LEDs to indicate the input and output voltages and the FAUL T pin signal.Design files for this circuit board are available at /demo/DC1555CSYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V IN Board Input Voltage Range–3030V V IN(UVLO)Input Supply Undervoltage Lockout V IN Rising 1.8 2.2 2.4VI VIN Input Supply Current SHDN = 0VSHDN = 2.5V 102550150µAµAI VIN(R)Reverse Input Supply Current V IN = –40V, V OUT = 0V–1.2–1.8mAΔV GATE External N-Channel Gate Drive (GATE – V OUT)V IN = V OUT = 5V, I GATE = –1µAV IN = V OUT = 12V to 34V, I GATE = –1µA37.43.68.44.29.8VVI GATE(UP)External N-Channel Gate Pull-Up current GATE = V IN = V OUT = 12V–12–20–30µA I GATE(FAST)External N-Channel Fast Gate Pull-Down Current Fast Shutdown, GATE = 20V, V IN = V OUT = 12V315072mA I GATE(SLOW)External N-Channel Gentle Gate Pull-Down Current Gentle Shutdown, GATE = 20V, V IN = V OUT = 12V5090150µA V UV UV Input Threshold Voltage UV Falling → ΔV GATE = 0V492.5500507.5mV V OV OV Input Threshold Voltage OV Rising → ΔV GATE = 0V492.5500507.5mV t GATE(FAST)External N-Channel Fast Gate Turn-Off Delay C GATE = 2.2nF, UV or OV Fault24µs t FAUL T OV, UV Fault Propagation Delay Overdrive = 50mV, V IN = V OUT = 12V12µs V SHDN SHDN Input Threshold SHDN Falling to ΔV GATE = 0V0.40.75 1.2V1dc1555cfb2dc1555cfboperating principlesThe LTC4365/LTC4365-1 monitors the input rail voltage and disconnects downstream circuits when the input volt-age is too low, too high or negative. The LTC4365 provides accurate overvoltage and undervoltage comparators to ensure that power is applied to the system only if the input supply is within the allowable voltage window. ReverseDemonstration circuit 1555C is easy to set up to evaluate the performance of the LTC4365/LTC4365-1. Refer to Figures 1a and 1b for proper measurement equipment setup and follow the procedure below.Note that the circuit on the DC1555C is optimized for 12V operation. The Si4230 FET limits overvoltage and reverse voltage to 30V and –30V, respectively. Refer to the LTC4365 data sheet for applications optimized for other voltages.Reverse Voltage Tests (Figure 1a)1) Set JP1 to EN.2) Set JP2 and JP3 to CONNECT LED.3) Connect a power supply across V IN and GND in a nega-tive configuration (connect positive rail to GND and negative rail to V IN ).4) Connect voltmeters at the input and output and ammeter in series with supply.5) Ramp supply down to –30V (referenced to GND).6) Verify that the output voltage is between 0V and –0.5V, all LEDs are off, and the input current is <1.8mA. (FET leakage or other board leakage paths can pull V OUT slightly negative, but it will be clamped by the internal protection diode.)7) Ramp supply back to 0V.Quick start proceDuresupply protection circuit automatically isolates the load from negative input voltages.During normal operation, a high voltage charge pump enhances the gate of external N-channel power MOSFETs. The controller consumes 10µA during shutdown and 125µA while operating.Undervoltage/Overvoltage Test (Figure 1b)8) Reverse the polarity of power supply connection across V IN to GND (connect positive rail to V IN and negative rail to GND).9) Ramp supply up to 30V and verify green V IN LED, red FAUL T LED, green V OUT LED, and V OUT according to Table 1 within the various voltage ranges.10) Ramp supply down from 30V down to 0V and verify green V IN LED, red FAUL T LED, green V OUT LED, and V OUT according to Table 1.11) Repeat steps 9 and 10 with 8A load connected acrossV OUT and GND.Table 1V IN V OUT V IN LED V OUT LED FAUL T LED0V to 5.77V = 0V Off/Dim/OnOff On 6.56V to 13.51V = V IN On On Off 15.47V to 30V= 0VOnOffOnJumper Test12) Remove load and set supply to 9V.13) Move jumpers and verify LEDs according to Table 2.Table 2JP1JP2/JP3VIN LED VOUT LED EN CONNECT LED On On DIS CONNECT LEDOn Off ENOpenOffOffQuick start proceDureFigure 1a. Reverse Voltage MeasurementFigure 1b. Undervoltage/Overvoltage Measurement3dc1555cfbparts listITEM QUANTITY REFERENCE DESCRIPTION MANUFACTURERS PART NUMBER 13CLD1, CLD2, CLD3 Current Limiting, Diode SOD-80Central Semi. Corp. CCLM2000 TR 20C1 (OPT)Cap., X5R 4.7µF 50V 20% 1210Taiyo Yuden UMK325BJ475MM-T 30C2 (OPT)Cap., Alum 47µF 35V 10% SANYO 35CE47AX40C3 (OPT)Cap., X7R 1000pF 50V 10% 0805AVX 08055C102KAT1A52D1, D2 LED, GRN Rohm Semi. SML-010FTT86L61D3 LED, RED Rohm Semi. SML-010VTT86L71D4 Diode, 75V/200mW SOD-523Diodes Inc. 1N4148WT80D5 (OPT)Zener Diode, 15V SOD-523Diodes Inc. BZT52C15T #PBF90D6 (OPT)Zener Diode, 20V POWERDI-123Diodes Inc. DFLT20A #PBF100D7 (OPT)Zener Diode, 40V POWERDI-123Diodes Inc. DFLT40A #PBF114E1, E2, E6, E7 Turret, Testpoint Mill Max 2501-2-00-80-00-00-07-0 124E3, E4, E5, E8 Turret, Testpoint Mill Max 2308-2-00-80-00-00-07-0 133JP1, JP2, JP3 Headers, Single Row 3 Pins 2mm Ctrs.SULLINS NRPN031PAEN-RC141Q1 Dual N-Channel, 30V SO-8Vishay Si4214DY-T1-GE3(AL T) Vishay SI4230DY-T1-GE3 150Q2 (OPT)Dual N-Channel, Low Current SOT-563 Diodes Inc. 2N7002V-7161R1 Res., Chip 1M 0.1W 1% 0603Vishay CRCW06031M00FKEA171R2 Res., Chip 54.9K 0.1W 1% 0603Vishay CRCW060354K9FKEA181R3 Res., Chip 36.5K 0.1W 1% 0603Vishay CRCW060336K5FKEDA191R4 Res., Chip 510K 0.1W 5% 0603Vishay CRCW0603510KJNEA203XJP1, XJP2, XJP3 Shunt, 2mm Ctrs.Samtec 2SN-BK-G214Stand-Off, Nylon 0.25" Tall Keystone, 8831(Snap On)221U1I.C., Overvoltage, Undervoltage and Reverse SupplyLinear Technology Corp. LTC4365CTS8Protection Controller for DC1555C-ALinear Technology Corp. LTC4365CTS8-1 221U1I.C., Overvoltage, Undervoltage and Reverse SupplyProtection Controller for DC1555C-B4dc1555cfb5dc1555cfbInformation furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.schematic Diagram6dc1555cfbLinear Technology Corporation1630 McCarthy Blvd., Milpitas, CA 95035-7417(408) 432-1900 ● FAX : (408) 434-0507 ● www.linear .comLINEAR TECHNOLOGY CORPORA TION 2011LT 0713 REV B • PRINTED IN USADEMONSTRATION BOARD IMPORTANT NOTICELinear Technology Corporation (L TC) provides the enclosed product(s) under the following AS IS conditions:This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONL Y and is not provided by L TC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT , SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.The user assumes all responsibility and liability for proper and safe handling of the goods. Further , the user releases L TC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.).No License is granted under any patent right or other intellectual property whatsoever. L TC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.L TC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive .Please read the DEMO BOARD manual prior to handling the product . Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged .This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a L TC applica-tion engineer .Mailing Address:Linear Technology 1630 McCarthy pitas, CA 95035Copyright © 2004, Linear Technology Corporation。
lt3724 高压电流模式降压转换器演示电路 dc736a 用户手册说明书
Description High Voltage Current Mode Step-Down ConverterDemonstration Circuit 736A is a 200kHz high voltage, current-mode DC/DC step-down converter featuring the L T®3724.The circuit operates from a V IN range of 30V to 55V and outputs 24V at 3A (72W). A soft-start feature controls the output voltage slew rate at start-up, reducing current surges and voltage overshoots. Burst Mode® operation that improves the efficiency at light loads can be enabled with a jumper.An optional boost bias circuit is provided on the bottom side of the board for back-driving the LT3724 internal regulator from the output voltage. Customers might want to use this optional circuit with modified applications that have relatively high input voltages and low (~5V) output voltages. In such applications, the optional circuit can increase the overall efficiency by reducing the power lostperformance summary in the LT3724. The demonstration circuit has also been layed out with the option for a second switching MOSFET to facilitate higher output currents. The circuit design can be modified for a boost converter configuration.This circuit is suitable for a wide range of Industrial control systems and particularly suitable for 12V/42V automotive applications and 48V Telecom power supplies.The LT3724 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this demo manual. Design files for this circuit board are available at /demoL, L T, L TC, L TM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.Specifications are at T A = 25°CPARAMETER CONDITIONS MIN TYP MAX UNITS Input Voltage Range3055VEfficiency V IN = 30V, I OUT = 3.0AV IN = 48V, I OUT = 3.0AV IN = 55V, I OUT = 3.0A 97.495.494.7%%%Switching Frequency200kHz Output Voltage I OUT = 0A to 3.0A24V Output Voltage Ripple V IN = 48V, I OUT = 3.0A 100mV1dc736af2dc736afQuick start proceDureDC736A is easy to set up to evaluate the performance of the LT3724. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below:NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscil-loscope probe. See Figure 2 for the proper scope technique. 1. Place JP1 in the RUN position.2. Place JP2 in the desired operating mode: fixed frequency or Burst Mode operation.3. With power off, connect the input power supply to V IN and GND.4. With power off, connect the load to V OUT and GND.5. Turn on the power at the input and adjust the input voltage until the LT3724 turns on. NOTE: Make sure that the input voltage does not exceed 55V.6. Check for the proper output voltage.NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high or is shorted.7. Once the proper output voltage is established, adjust the input voltage and load within the operating range and observe the output voltage regulation, ripple voltage,efficiency and other parameters.Figure 1. Proper Measurement Equipment SetupFigure 2. Measuring Output Rippleparts ListITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER11CIN1Cap., Aluminum 68µF 63V 20%Sanyo 63MV68AX-T22CIN2, CIN3 Cap., X7R 2.2µF 100V 20%TDK C4532X7R2A225M31COUT1 Cap., Alum 330µF 35V 10%Sanyo 35CV330AX-T42COUT3, COUT2 Cap., X7R 22µF 25V 20%TDK C5750X7R1E226M51C1 Cap., NPO 1000pF 100V 10%AVX 08051A102KAT1A61C2 Cap., X5R 0.22µF 16V 10%Taiyo Yuden EMK107BJ224KA71C3 Cap., X7R 1000pF 25V 10%AVX 04023C102KAT2A81C4 Cap., X5R 0.1µF 16V 10%AVX 0402YD104KAT2A91C5 Cap., X5R 1µF 16V 10%Taiyo Yuden EMK212BJ105KG101C6 Cap., X7R 120pF 25V 10%AVX 04023C121KAT2A111C7 Cap., X7R 1500pF 16V 20% 0402AVX 0402YC152MAT2A121C12Cap., X7R 0.01µF 16V 10%AVX 0402YC103KAT2A131D1 Diode, Speed Switching Diodes Inc. BAS19141D2 Schottky Diode 60V IR 30BQ060151D5Diode, 75V/200mW Diodes Inc. 1N4148WS161L1 Inductor, 47µH Coilcraft DO5040H-473MLB171Q1 MOSFET N-Channel, PowerPak SO8 Vishay Siliconix Si7852DP181R1 Res, Chip 1M 0.1W 5%AAC CR10-105JM191R2 Res/Jumper, Chip 0Ω 0.06W 1A AAC CJ05-000M201R3 Res., Chip 52.3k 1/16W 1%Vishay CRCW0402 52.3K 1%211R4 Res., Chip 402K 1/16W 1%AAC CR05-4023FM221R5 Res., 0.025 0.5W 1%IRC LRF2010-01-R025-F231R6 Res., Chip 1M 0.1W 5%AAC CR16-105JM241R7 Res., Chip 4.99k 0.06W 1%AAC CR05-4991FM251R8 Res., Chip 93.1k 1/16W 1%AAC CR05-9312FM261R9 Res., Chip 2.21k 1/16W 1%AAC CR05-2211FM271R14Res., Chip 470 1/16W 5%AAC CR05-471JM281R15Res., Chip 47k 1/16W 5%AAC CR05-473JM291U1 I.C., Voltage Regulator Linear Technology Corporation LT3724EFE Additional Demo Board Circuit Components10C8 Cap., X5R C-4.7µF, 6.3V-0805 6.3V 20%Taiyo Yuden JMK212BJ475MG-T20C9 Cap., X5R 1µF 16V 20%Taiyo Yuden EMK212BJ105MG30C10 Cap., NPO 220pF 25V 10%AVX 04023A221KAT2A40C11Cap., Aluminum 22µF 35V 10%Sanyo 35MV22UAX50D3,D4 Schottky Diode, 40V Zetex ZHCS40060L2 Inductor, L-10µH Murata LQH3C100M2470R10 Res./Jumper, Chip 0Ω 0.06W 1A AAC CJ05- 000M80R11 Res., Chip 107k 0.06W 1%AAC CR05-1073FM90R12 Res., Chip 10k 0.06W 5%AAC CR05-103JM100R13 Res., Chip 12.4k 1/16W 1%AAC CR05-1242FM110U2 I.C., Voltage Regulator Linear Technology Corporation LT1613CS53dc736afparts ListITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Hardware – For Demo Board Only14E1, E2, E3, E4 Testpoint, Turret Mill Max 2501-220E5 Testpoint, Turret Mill Max 2501-232JP2, JP1 Headers, 3 Pins 2mm Ctrs. Comm Con Connectors 2802S-03G242XJP1, XJP2JMP, 3 Pin 1 Row .079CC Comm Con Connectors CCIJ2MM-138GW 4dc736af5dc736afInformation furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.schematic Diagram6dc736afLinear Technology Corporation1630 McCarthy Blvd., Milpitas, CA 95035-7417(408) 432-1900 ● FAX : (408) 434-0507 ● www.linear .comLINEAR TECHNOLOGY CORPORA TION 2012LT 0912 • PRINTED IN USADEMONSTRATION BOARD IMPORTANT NOTICELinear Technology Corporation (L TC) provides the enclosed product(s) under the following AS IS conditions:This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONL Y and is not provided by L TC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT , SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.The user assumes all responsibility and liability for proper and safe handling of the goods. Further , the user releases L TC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.).No License is granted under any patent right or other intellectual property whatsoever. L TC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.L TC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive .Please read the DEMO BOARD manual prior to handling the product . Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged .This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a L TC applica-tion engineer .Mailing Address:Linear Technology 1630 McCarthy pitas, CA 95035Copyright © 2004, Linear Technology Corporation。
DSC-CN3704
如韵电子 CONSONANCE Rev 1.25A 四节锂电池充电管理集成电路CN3704概述:CN3704是PWM 降压模式四节锂电池充电管理集成电路，独立对四节锂电池充电进行自动管理，具有封装外形小，外围元器件少和使用简单等优点。
CN3704具有恒流和恒压充电模式，非常适合锂电池的充电。
在恒压充电模式，CN3704将电池电压调制在16.8V ，精度为±1%；在恒流充电模式，充电电流通过一个外部电阻设置。
对于深度放电的锂电池，当电池电压低于11.2V 时，CN3704用所设置的恒流充电电流的15%对电池进行涓流充电。
在恒压充电阶段，充电电流逐渐减小，当充电电流降低到外部电阻所设置的值时，充电结束。
在充电结束状态，如果电池电压下降到16V 时，自动开始新的充电周期。
当输入电源掉电或者输入电压低于电池电压时，CN3704自动进入睡眠模式。
其它功能包括输入低电压锁存，电池温度监测，电池端过压保护和充电状态指示等。
CN3704采用16管脚TSSOP 封装。
应用:●笔记本电脑，上网本 ● 航模，车模和船模等 ● 备用电池应用● 便携式工业和医疗仪器 ● 电动工具● 独立电池充电器特点:● 宽输入电压范围：7.5V 到28V ● 对四节锂电池完整的充电管理 ● 充电电流达5A● PWM 开关频率：300KHz ● 恒压充电电压精度： ±1% ● 恒流充电电流由外部电阻设置 ● 对深度放电的电池进行涓流充电 ● 充电结束电流可由外部电阻设置 ● 电池温度监测功能 ● 自动再充电功能● 充电状态和充电结束状态指示 ● 软启动功能 ● 电池端过压保护 ● 工作环境温度：－40℃ 到 ＋85℃ ● 采用16管脚TSSOP 封装 ●产品无铅，无卤素元素，满足RoHS管脚排列:BAT VCC DRV COM2COM3NC test CSP典型应用电路:图1 典型应用电路订购信息:管脚描述:极限参数VCC，VG，DRV，CHRG，DONE到GND的电压…….…－0.3V to 30VCSP，BA T到GND的电压………………………………..…－0.3V to 28VCOM3到GND的电压…………………………………...…….6.5V其它管脚到GND的电压………………………..........………－0.3V to V COM3+0.3V存储温度……………………………………………...……..…－65℃---150℃工作环境温度………………………….…………………….…－40℃---85℃焊接温度(10 秒)…………………………………………..……300℃超出以上所列的极限参数可能造成器件的永久损坏。
lt3474原理 -回复
lt3474原理-回复首先，我们将从基础知识开始，介绍LT3474的工作原理。
LT3474是一种具有恒定频率、开关电源的DC/DC转换器，专为输出电流较高的应用而设计。
它能够在大范围的输入电压下提供稳定的输出电压，并具有高效率和低电流纹波。
LT3474转换器的工作原理可以分为以下几个步骤：1. 输入电压稳压：输入电源将直流电源通过端子IN输入转换器。
转换器中的输入电压稳压电路通过使用反馈电压来控制MOSFET的开关状态，以稳定输入电压。
2. 输出电压调整：转换器将输入电压经过电感L和二极管D1转换为脉冲信号，并通过滤波电容C进行平滑处理。
这个过程产生了一个短时脉冲的高电压。
然后，通过使用反馈电路对这个高电压进行调整，以达到所需的输出电压。
如果输出电压低于设定值，反馈电路将相应地增大PWM控制电路的占空比，以增加输出电压。
相反，如果输出电压高于设定值，反馈电路将减小占空比。
3. PWM控制：利用PWM（脉宽调制）控制方式来实现稳定输出电压。
PWM控制电路根据反馈电路的信号和设定值生成一个脉冲宽度调制信号，并通过控制开关管的导通时间来调整输出电压的大小。
脉冲信号的频率通常是在几十kHz到几MHz之间，具体取决于应用需求。
4. 开关管控制：转换器的核心部分是MOSFET开关管。
PWM控制电路通过调整开关管的导通和关断时间来控制输出功率的大小。
当开关管导通时，输入电流通过电感L和开关管Q流入电容C。
然后，在开关管关闭时，电感L产生一个反向电流，通过二极管D2供电给负载。
5. 输出滤波：输出电压通过滤波电容C进行平滑处理，以减小输出电压的纹波及噪声。
总结起来，LT3474的工作原理包括输入电压稳压、输出电压调整、PWM 控制、开关管控制和输出滤波。
通过这些步骤，LT3474能够将输入电压转换为稳定的输出电压，以满足各种应用的需求。
宽输入范围DC／DC控制器
宽输入范围DC／DC控制器
佚名
【期刊名称】《今日电子》
【年(卷),期】2011(000)011
【摘要】LT3759具有两个电压反馈误差放大器和基准电压。
一组用于正输出电压，另一组则用于鱼输出电压，它们均利用单个反馈引脚进行调节，从而使LT3759成为一款适合多种电源设计的高通用型DC／DC控制器。
【总页数】1页(P67-67)
【正文语种】中文
【中图分类】TN713
【相关文献】
1.一种宽输入电压范围软开关电流型DC/DC转换器 [J], 朱浩亮
2.凌力尔特公司推出宽输入范围DC／DC控制器LT3759 [J],
3.凌力尔特推出宽输入电压范围降压型DC／DC控制器 [J],
4.宽输入电压范围Z源谐振DC-DC变换器 [J], 柏方泉;沈锦飞
5.宽输入范围降压型DC/DC控制器 [J],
因版权原因，仅展示原文概要，查看原文内容请购买。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
宽输入电压范围正变负DC-DC控制器LTC3704LTC3704系新设计的一款正压转成负压输出的非隔离控制IC。
是目前转换效率最佳，外接元件最少，输出功率可大可小的一款新品。
由于不用检测电流的R SENSE，而用外部功率MOSFET的R SD(ON)做过流检测，控制IC的工作频率可从50KHz~1MHz，还可以同步到外时钟，设计的猝发工作模式可以使其在轻载时消耗极低，仅10μA。
其它特点如下：●宽输入电压范围，从2.5V~36V。
●电流型控制，有极好的瞬态响应。
●最大占空比达92%。
●+/-1%的内部电压基准。
●小型封装缩小了占空面积。
LTC3704的内部等效电路如图1。
简单应用电路如图2。
图1 LTC3704的内部等效方框电路LTC3704的10个引脚功能如下：RUN 1PIN, RUN端子提供给用户用一个精准检测输入电压并调节变换器的起动阈值。
将此端降到1.248V时，IC关断。
其有100mV窗口，此端低于此电压时，IC工作电流仅10μA，最大起动运行电压可调至7V。
ITH 2PIN，误差放大器补偿端。
电流比较器输入阈值跟随此端电压增长，正常电压范围为0V~1.40V。
NFB 3PIN，接收反馈电压，用外接电阻分压器接到输出，正常时此端电压为-1.230V。
FREQ 4PIN，外接一支电阻到GND，设置工作频率。
正常状态电压约0.62V。
MODE/SYNC 5PIN，该端输入控制其工作模式，外同步信号也从此端送入。
如果MODE/SYNC端接地，即使能猝发工作模式。
如果接至INT Vcc或外部逻辑电平的同步信号，猝发工作模式即被禁止，IC仅工作在连续模式。
GND 6PIN，IC公共端。
GATE 7PIN，栅驱动输出端。
INTVcc 8PIN，内部5.2V稳压器输出，供给栅驱动电路，需外接去耦电容，为4.7uf低ESR的瓷电容。
V IN 9PIN，IC的供电端，需外接旁路电容。
SENSE 10PIN，电流检测输入给控制环。
将此端接至外部功率MOSFET的漏极，利用V SDON作过流检测，以提高效率。
内部前沿消隐也由此端提供，此端共计两个功能。
图2 LTC3704的基本应用电路下面描述其工作:工作原理主控制环路LTC3704是一个用于DC/DC正压至负压变换器应用的恒频电流型控制器。
LTC3704与传统的电流型控制器有所不同，因为电流控制环路可通过检测功率MOSFET开关(而不是一个分立的检测电阻)两端的压降来闭合，如图3所示。
这种检测技术提高了效率和功率密度，并降低了总体解决方案的成本。
图3 SENSE端的应用方法关于电路的工作原理，请参见图1和图2。
在正常工作状态下，当振荡器设定PWM锁存器时，功率MOSFET导通。
当电流比较器C1将锁存器复位时，功率MOSFET关断。
由误差放大器EA将经过分压的输出电压与一个内部1.230V 基准进行比较，并在I TH引脚上输出一个误差信号。
I TH引脚上的电压设定电流比较器C1的输入门限。
当负载电流增加时，NFB电压相对于基准电压的下降使I TH引脚电平上升，这导致电流比较器C1在一个更大的峰值电感电流值上发生跳变。
因此，平均电感电流将增加，直到与负载电流相等，由此保持输出稳定。
LTC3704的标称工作频率是采用一个从FREQ引脚连接到地的电阻来设定的，其受控范围为50KHz至1000KHz。
此外，IC内部的振荡器可以与一个加在MODE/SYNC引脚上的外部时钟同步，并能够锁定在其标称值100%到130%之间的某一频率上。
当MODE/SYNC引脚处于开路状态时，用一个50K的内部电阻将该引脚的电平拉低，并使能突发方式操作。
如果该引脚的电平高于2V，或被施加了一个外部时钟，则突发方式操作失效。
IC仅工作于连续方式。
在没有负载(或负载极小)的情况下，控制器将进行跳跃脉冲操作以保持稳定状态，并防止出现过大的输出波纹。
RUN引脚用来控制IC是处于使能状态还是低电流的停机状态。
微功率的1.248V基准和比较器C2允许用户设置IC导通和关断的电源电压(比较器C2具有用于实现噪声免疫的100mV迟滞)。
RUN引脚电平低于1.248V时，芯片关断,输入电源电流的典型值只有10μA。
如图3所示，LTC3704的使用既可以通过检测功率MOSFET两端的压降来完成，也可以通过把SENSE引脚与位于功率MOSFET源极的一个普通分流电阻相连接来完成。
检测功率MOSFET两端电压的方法最大限度地提高了变换器的效率，并最大限度地减少了元件的数量。
但将输出电压限制为该引脚的最大额定值(36V)，通过把SENSE引脚与位于功率MOSFET源极的电阻相连接，用户能够对该IC的36V最大额定输入电压高得多的输出电压进行设置。
●操作方式的设置对于那些优先考虑最大限度地提高轻负载条件下(例如，小于100μA)的效率应用来说，应该采用突发方式操作(即MODE/SYNC引脚应与地相连)。
而在那些固定频率操作较低电流效率更为重要，或需要最小输出波纹的应用中，应采用脉冲跳跃方式操作，且MODE/SYNC引脚应与INTVcc引脚相连接。
这就使得不连续导通方式(DCM)操作的时间被减少到接近由芯片的最少导通时间(约175ns)所规定的限值。
在此输出电流电平以下，变换器将执行跨越周期的操作以保持输出稳定。
图4跳变和图5示出了图2中变换器的突发方式和脉冲跳变方式操作的轻负载开关波形。
●猝发方式操作猝发方式工作是通过MODE/SYNC引脚置于空置或将其接地来选择的。
在正常工作状态下，I TH引脚上对应空载至满载的电压范围为0.30V至1.2V。
在猝发方式操作中，如果误差放大器EA把I TH电压驱动至0.525V以下时，电流比较器C1的缓冲I TH输入将被箝位于0.525V(它对应于最大负载电流的25%)。
这样，电感器峰值电流保持在大约30mV，用功率MOSFET的R DS(ON)相除，如果I TH引脚电平降至0.30V以下，猝发方式比较器B1将关断功率MOSFET，并把IC的静态电流按比例变到250μA(休眠方式)。
在这种条件下，负载电流将由输出电容器提供，直到I TH电压升至猝发比较器的50mV迟滞以上。
在轻载条件下，将观察到在短时的猝发开关(平均电感器电流是其最大值的25%)之后是较长的休眠期，由此极大地提高了变换器效率。
图3示出了描绘突发方式操作的示波器波形。
图4 轻载下的猝发工作模式图5 禁止猝发模式工作的波形●跨跃脉冲方式操作将MODE/SYNC引脚与一个大于2V的DC电压相连后，猝发方式操作失效。
内部的0.525V缓冲I TH猝发箝位被取消，使得I TH引脚在空载到满载的条件下直接控制电流比较器。
空载时，I TH引脚被驱动至0.30V以下，功率MOSFET被关断并进入休眠方式。
图5示出了描绘这种操作方式的波形。
当一个外部时钟信号以高于芯片内部振荡器频率的速率对MODE/SYNC引脚进行驱动时，振荡器将与之同步。
在这种同步方式中。
猝发模式工作失效。
与同步工作相关联的恒定频率由变换器提供了一个更加受控的噪声频谱，代价是牺牲轻载条件下的总体系统效率。
当振荡器的内部逻辑电路在MODE/SYNC引脚上检测到一个同步信号时，内部振荡器斜坡上升被提前终止，斜率补偿增加了大约30%。
因此，在要求同步的应用中，建议将IC的标称工作频率设置为外部时钟频率的75%左右。
如果试图与更高的外部频率(1.3 Fo以上)同步，则会导致斜率补偿不足以抑制次谐波振荡(或抖动)。
外部时钟信号必须超过2V脉宽至少达到25ns以上，而且应具有80%的最大占空比，如图6所示。
MOSFET的导通将与外部时钟信号的上升沿同步。
●工作频率的设置工作频率和电感值的选择是对效率和元件尺寸权衡之后的折衷。
低频工作通过降低MOSFET和二极管的开关损耗提高了效率。
然而，对于给定的负载电流值，较低的工作频率要求采用更大的电感。
LTC3704采用一种恒定频率结构，利用一个从FREQ引脚连接到地的外部电阻在50KHz至1000KHz的范围内进行设置，如图1所示.FREQ引脚上的标称电压为0.6V，流入FREQ引脚的电流被用来对一个内部振荡电容器进行充放电。
图7示出了对于给定工作频率情况下选择的R T值图形。
图6 外同步时的时钟和工作波形图7 定时电阻和工作频率INTVcc稳压器旁路和操作如图8所示。
一个内部沟道低压降稳压器生成了为LTC3704内的驱动器和逻辑电路供电的5.2V电源。
INTVcc稳压器能够提供高达50mA的电流，且必须通过一个紧靠着IC引脚而最小值为4.7uf的钽电容器或陶瓷电容器旁路到地。
对于MOSFET栅极驱动器所要求的大瞬态电流的提供而言，良好的旁路是必需的。
对于不超过7V(该引脚的绝对最大额定值)的输入电压，LTC3704中的内部低压降稳压器是多余的，INTVcc引脚可以直接短接至V IN引脚。
然而，当INTVcc 引脚短接至V IN引脚时，设置稳定INTVcc电压的分压器将从输入电源吸收10μA的电流，即使在待机状态下也是如此。
对于那些要求最低待机方式输入电源电流的应用，不要把INTVcc引脚与V IN相连。
不管INTVcc引脚是否短接至VI N，必需始终通过一个紧挨着INTVcc和GND引脚的4.7uf钽电容器或低ESR陶瓷电容器把驱动器电路旁路到地。
图8 对LDO连接的旁路电容及外功率MOSFET的驱动在实际应用中，大多数IC电源电流被用来驱动功率MOSFET的栅电容。
因此，对大功率MOSFET进行高频驱动的高输入电压应用可能会使LTC3704超过其最大额定结温，可以利用下列公式来估算结温：总静态电流I Q(TOT)由静态工作电流(I Q)和用于对功率MOSFET的栅极进行充放电所需的电流组成。
10引脚MSOP封装具有R TH(JA)=120℃/W的热阻。
举个例子，假设有一个V IN=5V且V SW(MAX)=12V的电源。
开关频率为500KHz,最高环境温度为70度。
选择的功率MOSFET是IRF7805，其最大导通电阻R DS(ON)为11mΩ(室温条件下)，最大栅极电荷量为37nC (栅极电荷的温度系数较小)。
这表明了与IC中的静态电流相比，栅极充电电流有多么重要。
为了防止超过最高结温，当在高的V IN条件下的连续方式工作也需检查输入电源电流，可能需要在工作频率与功率MOSFET大小之间进行权衡，以保持可靠的IC结温。
然而，在降低工作频率之前，一定要和功率MOSFET制造商核对他们最新﹑最顶级的低Q G﹑低R DS(ON)器件。
功率MOSFET制造技术正在不断改进，几乎每年都会推出更新和性能更好的器件。
●输出电压设置输出电压由一个电阻分压器按照下式进行设定：其中，V REF=-1.230V，I NFB是流出NFB引脚的电流(I NFB=-7.5μA)。