MAX1928EUB18-T中文资料

REF
PGND GND
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19-2527; Rev 0; 7/02
Low-Output-Voltage, 800mA, PWM Step-Down DC-DC Converters
General Description
The MAX1927/MAX1928 800mA step-down converters power low-voltage microprocessors in compact equipment requiring the highest possible efficiency. The MAX1927/MAX1928 are optimized for generating low output voltages (down to 750mV) at high efficiency using small external components. The supply voltage range is from 2.6V to 5.5V and the guaranteed minimum output current is 800mA. 1MHz pulse-width modulation (PWM) switching allows for small external components. A unique control scheme minimizes ripple at light loads, while maintaining a low 140µA quiescent current. The MAX1927/MAX1928 include a low on-resistance internal MOSFET switch and synchronous rectifier to maximize efficiency and minimize external component count. No external diode is needed. 100% duty-cycle operation allows for a dropout voltage of only 340mV at 800mA. Other features include internal soft-start, power-OK (POK) output, and selectable forced PWM operation for lower noise at all load currents. The MAX1928 is available with several preset output voltages: 1.5V (MAX1928-15), 1.8V (MAX1928-18), and 2.5V (MAX1928-25). The MAX1927R has adjustable output range down to 0.75V. The MAX1927/MAX1928 are available in a tiny 10-pin µMAX package. o 800mA Output Current o Output Voltages from 0.75V to 5V o 2.6V to 5.5V Input Voltage Range o Power-OK Output o No Schottky Diode Required o Selectable Forced PWM Operation o 1MHz Fixed-Frequency PWM Operation o 140µA Quiescent Current o Soft-Start o 10-Pin µMAX Package
Applications
WCDMA Handsets PDAs and Palmtops DSP Core Power Battery-Powered Equipment
MAX1928EUB15 MAX1928EUB18 MAX1928EUB25
Pin Configuration
TOP VIEW
PWM 1 GND REF FB COMP 2 3 4 5 10 POK 9 BATT
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
1.269 2 0.4 0.5 0.3 0.35
V mV
Ω Ω V/A A A A
2
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Transconductance (gm)
µS
Reference Voltage Accuracy Reference Supply Rejection PWM CONTROLLER P-Channel On-Resistance N-Channel On-Resistance Current-Sense Transresistance (RCS ) P-Channel Current-Limit Threshold P-Channel Pulse-Skipping Current Threshold N-Channel ive Current-Limit Threshold
ELECTRICAL CHARACTERISTICS
(VBATT = 3.6V, SHDN = BATT, CREF = 0.1µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER BATT Input Voltage Undervoltage Lockout Threshold Quiescent Current Quiescent Current in Dropout Shutdown Supply Current REFERENCE AND ERROR AMP MAX1927R FB Voltage Accuracy MAX1928-15 MAX1928-18 MAX1928-25 FB Input Current MAX1928 MAX1927R MAX1927R MAX1928-15 MAX1928-18 MAX1928-25 1.231 2.6V < VBATT < 5.5V VBATT = 3.6V VBATT = 2.6V VBATT = 3.6V VBATT = 2.6V 1.1 0.11 0.738 1.477 1.773 2.462 5 0.75 1.5 1.8 2.5 10 10 250 210 175 125 1.25 0.5 0.25 0.3 0.17 0.2 0.48 1.3 0.13 -0.55 1.6 0.15 0.762 1.523 1.827 2.538 15 150 µA nA V SHDN = GND VBATT rising or falling (35mV hysteresis) No load, pulse skipping, PWM = GND 1MHz switching CONDITIONS MIN 2.6 2.15 2.35 140 2 190 0.1 340 10 TYP MAX 5.5 2.55 240 UNITS V V µA mA µA µA
VIN 2.6V TO 5.5V
Typical Operating Circuit
PWM L1 LX SHDN RC COMP CC Cf FB C2 VOUT 0.75V AT 800mA
BATT C1
MAX1927R MAX1928
8 LX 7 PGND 6 SHDN
MAX1927R
POK
µMAX
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Low-Output-Voltage, 800mA, PWM Step-Down DC-DC Converters MAX1927/MAX1928
ABSOLUTE MAXIMUM RATINGS
BATT, PWM, POK, COMP, SHDN to GND ...............-0.3V to +6V PGND to GND .......................................................-0.3V to +0.3V LX, REF, FB to GND ................................-0.3V to (VBATT + 0.3V) Continuous Power Dissipation (TA = +70°C) 10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C
Features
MAX1927/MAX1928
Ordering Information
PART MAX1927REUB PRESET TEMP PINOUTPUT PACKAGE RANGE VOLTAGE Adj. to 0.75V -40°C to +85°C 10 µMAX 1.5V 1.8V 2.5V -40°C to +85°C 10 µMAX -40°C to +85°C 10 µMAX -40°C to +85°C 10 µMAX
Low-Output-Voltage, 800mA, PWM Step-Down DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 3.6V, SHDN = BATT, CREF = 0.1µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)