UC3843D中文资料

UC3842
Figure 1. Open Loop Test Circuit
High peak currents associated with capacitive loads necessitate careful grounding techniques Timing and bypass capacitors should be connected close to pin 5 in a single point ground. The transistor and 5kΩ potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to pin 3.
UNDER-VOLTAGE LOCKOUT SECTION VTH(ST) VOPR(MIN)
3
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UC3842/UC3843/UC3844/UC3845
Electrical Characteristics (Continued)
(VCC=15V, RT=10kΩ, CT=3.3nF, TA= 0°C to +70°C, unless otherwise specified) Parameter PWM SECTION Max. Duty Cycle Min. Duty Cycle TOTAL STANDBY CURRENT Start-Up Current Operating Supply Current Zener Voltage IST ICC(OPR) VZ ICC = 25mA Vpin3=Vpin2=ON 30 0.45 14 38 1 17 mA mA V D(Max) D(Max) D(MIN) UC3842/UC3843 UC3844/UC3845 95 47 97 48 100 50 0 % % % Symbol Conditions Min. Typ. Max. Unit
1200 8DIP 1100 POWER DISSIPATION (mW) 1000 900 800 700 600 500 400 300
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
14SOP
8SOP
AMBIENT TEMPERATURE (℃)
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UC3842/UC3843/UC3844/UC3845
SMPS Controller
Features
• • • • Low Start up Current Maximum Duty Clamp UVLO With Hysteresis Operating Frequency up to 500KHz
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UC3842/UC3843/UC3844/UC3845
Absolute Maximum Ratings
Parameter Supply Voltage Output Current Analog Inputs (Pin 2.3) Error Amp Output Sink Current Power Dissipation at TA≤25°C (8DIP) Power Dissipation at TA≤25°C (8SOP) Power Dissipation at TA≤25°C (14SOP) Storage Temperature Range Lead Temperature (Soldering, 10sec) Symbol VCC IO V(ANA) ISINK (E.A) PD(Note1,2) PD(Note1,2) PD(Note1,2) TSTG TLEAD Value 30 ±1 -0.3 to 6.3 10 1200 460 680 -65 ~ +150 +300 Unit V A V mA mW mW mW °C °C
Note: 1. Board Thickness 1.6mm, Board Dimension 76.2mm ×114.3mm, (Reference EIA / JSED51-3, 51-7) 2. Do not exceeed PD and SOA (Safe Operation Area)
Power Dissipation Curve
UC3842/UC3843/UC3844/UC3845
Electrical Characteristics
(VCC=15V, RT=10kΩ, CT=3.3nF, TA= 0°C to +70°C, unless otherwise specified) Parameter REFERENCE SECTION Reference Output Voltage Line Regulation Load Regulation Short Circuit Output Current OSCILLATOR SECTION Oscillation Frequency Frequency Change with Voltage Oscillator Amplitude ERROR AMPLIFIER SECTION Input Bias Current Input Voltage Open Loop Voltage Gain Power Supply Rejection Ratio Output Sink Current Output Source Current High Output Voltage Low Output Voltage CURRENT SENSE SECTION Gain Maximum Input Signal Power Supply Rejection Ratio Input Bias Current OUTPUT SECTION Low Output Voltage High Output Voltage Rise Time Fall Time Start Threshold Min. Operating Voltage (After Turn On) VOL ISINK = 20mA ISINK = 200mA VOH tR tF ISOURCE = 20mA ISOURCE = 200mA TJ = 25°C, CL= 1nF (Note 3) TJ = 25°C, CL= 1nF (Note 3) UC3842/UC3844 UC3843/UC3845 UC3842/UC3844 UC3843/UC3844 13 12 14.5 7.8 8.5 7.0 0.08 1.4 13.5 13.0 45 35 16.0 8.4 10.0 7.6 0.4 2.2 150 150 17.5 9.0 11.5 8.2 V V V V ns ns V V V V GV VI(MAX) PSRR IBIAS (Note 1 & 2) Vpin1 = 5V(Note 1) 12V ≤ VCC ≤ 25V (Note 1,3) 2.85 0.9 3 1 70 -3 3.15 1.1 -10 V/V V dB µA IBIAS VI(E>A) GVO PSRR ISINK ISOURCE VOH VOL Vpin1 = 2.5V 2V ≤ VO ≤ 4V (Note3) 12V ≤ VCC ≤ 25V (Note3) Vpin2 = 2.7V, Vpin1 = 1.1V Vpin2 = 2.3V, Vpin1 = 5V Vpin2 = 2.3V, RL = 15kΩ to GND Vpin2 = 2.7V, RL = 15kΩ to Pin 8 2.42 65 60 2 -0.6 5 -0.1 2.50 90 70 7 -1.0 6 0.8 -2 2.58 1.1 µA V dB dB mA mA V V f ∆f/∆VCC VOSC TJ = 25°C 12V ≤ VCC ≤ 25V 47 52 0.05 1.6 57 1 kHz % VP-P VREF ∆VREF ∆VREF ISC TJ = 25°C, IREF = 1mA 12V ≤ VCC ≤ 25V 1mA ≤ IREF ≤ 20mA TA = 25°C 4.90 5.00 6 6 -100 5.10 20 25 -180 V mV mV mA Symbol Conditions Min. Typ. Max. Unit
8-DIP 8-SOP
1
1
14-SOP
1
Internal Block Diagram
* NORMALLY 8DIP/8SOP PIN NO. * ( ) IS 14SOP PINNO. * TOGGLE FLIP FLOP USED ONLY IN UC3844, UC3845
Rev. 1.0.1
©2002 Fairchild Semiconductor Corporation
Description
The UC3842/UC3843/UC3844/UC3845 are fixed frequencycurrent-mode PWM controller. They are specially designed for Off-Line and DC to DC converter applications with minimum external components. These integrated circuits feature a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator and a high current totempole output for driving a Power MOSFET. The UC3842 and UC3844 have UVLO thresholds of 16V (on) and 10V (off). The UC3843 and UC3845 are 8.5V(on) and 7.9V (off). The UC3842 and UC3843 can operate within 100% duty cycle. The UC3844 and UC3845 can operate with 50% duty cycle.
Adjust VCC above the start threshould before setting at 15V
Note: 1. Parameter measured at trip point of latch 2. Gain defined as: ∆ V pin1 A = ----------------- ,0 ≤ Vpin3 ≤ 0.8V ∆ V pin3 3. These parameters, although guaranteed, are not 100 tested in production.
Thermal Data
Characteristic Thermal Resistance Junction-ambient Symbol Rthj-amb(MAX) 8-DIP 100 8-SOP 265 14-SOP 180 Unit °C/W
Pin Array
8DIP,8SOP 14SOP
COMP 1
8
VREF
COMP 1
14 VREF
VFB 2
7
VCC
N/C
2
13
N/C
CURRENT SENSE
3
6
OUTPUT
VFB 3
12
VCC
RT/ CT 4
5 GND
N/C 4
11 PWR VC
CURRENT SENSE
பைடு நூலகம்
5
10 OUTPUT
N/C
6
9
GND
RT/C T 7
8
PWR GND
2
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