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Part: MAX746CSE
Category:
Power Management
-> Battery Management
Description: MAX746 High-Efficiency, Pwm, Step-Down, N-channel DC-DC Controller
Company: Maxim Integrated Products
Datasheet: Download MAX746CSE datasheet File size : 404 kB
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Datasheet text preview:
19-0192; Rev 1; 11/93
High-Efficiency, PWM, Step-Down, N-Channel DC-DC Controller
_______________General Description
The MAX746 is a high-efficiency, high-current, step-down DC-DC power-supply controller that drives external N-channel FETs. It provides 93% to 96% efficiency from a 6V supply voltage with load currents ranging from 50mA up to 3A. It uses a pulse-width-modulating (PWM) current-mode control scheme to provide precise output regulation and low output noise. The MAX746's 4V to 15V input voltage range, fixed 5V/adjustable (Dual-ModeTM) output, and adjustable current limit make this device ideal for a wide range of applications. High efficiency is maintained with light loads due to a proprietary automatic pulse-skipping control (Idle-ModeTM) scheme that minimizes switching losses by reducing the switching frequency at light loads. The low 950µA quiescent current and ultra-low 1.4µA shutdown current further extend battery life. External components are protected by the MAX746's cycleby-cycle current limit. The MAX746 also features a 2V ±1.5% reference, a comparator for low-battery detection or level translating, and soft-start and shutdown capability. T h e M A X 7 4 7--d i s c u s s e d i n a s e p a r a t e d a t a s h e e t -- functions similarly to the MAX746, but drives P-channel logic level FETs.
____________________________Features
o 93% to 96% Efficiency for 50mA to 3A Output Currents o 4V to 15V Input Voltage Range o Low 950µA Supply Current o 1.4µA Shutdown Current o Drives External N-Channel FETs o Fixed-Frequency Current-Mode PWM (Heavy Loads) o Idle-Mode PFM (Light Loads) o Cycle-by-Cycle Current Limiting o 2V ±1.5% Accurate Reference Output o Adjustable Soft-Start o Undervoltage Lockout o Precision Comparator for Power-Fail or Low-Battery Warning
MAX746
______________Ordering Information
PART MAX746CPE MAX746CSE MAX746C/D MAX746EPE MAX746ESE MAX746MJE TEMP. RANGE 0°C to +70°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -55°C to +125°C PIN-PACKAGE 16 Plastic DIP 16 Narrow SO Dice* 16 Plastic DIP 16 Narrow SO 16 CERDIP
________________________Applications
5V-to-3.3V Green PC Applications Notebook/Laptop Computers Personal Digital Assistants Battery-Operated Equipment Cellular Phones
* Contact factory for dice specifications.
__________Typical Operating Circuit __________________Pin Configuration
INPUT 6V TO 15V
V+
TOP VIEW
AV+ 40m
CP HIGH SHDN ON/OFF D LOW-BATTERY ETECTOR INPUT LBI REF SS OUT LBO CC FB AGND GND
LBO 1 LBI 2
1 6 GND 1 5 V+ 1 4 CP
MAX746
CS EXT 39µH
OUTPUT 5 V
440µF
SS 3 REF 4 SHDN 5 FB 6 CC 7 AV+ 8
MAX746
1 3 HIGH 1 2 EXT 1 1 AGND 1 0 CS 9 OUT
D LOW-BATTERY ETECTOR OUTPUT
DIP/SO
TMDual-Mode and Idle-Mode are trademarks of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
High-Efficiency, PWM, Step-Down, N-Channel DC-DC Controller MAX746
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V+, AV+ to GND ......-0.3V to 17V HIGH, EXT to GND....-0.3V to 21V AGND to GND..........-0.3V to 0.3V All Other Pins......-0.3V to (V+ + 0.3V) Reference Current (IREF) ....±2mA Continuous Power Dissipation (TA = +70°C) Plastic DIP (derate 10.53mW/°C above +70°C) ..........842mW Narrow SO (derate 8.70mW/°C above +70°C) ...696mW CERDIP (derate 10.00mW/°C above +70°C) ......800mW Operating Temperature Ranges: MAX746C_E ........0°C to +70°C MAX746E_E .....-40°C to +85°C MAX746MJE ........-55°C to +125°C Junction Temperatures: MAX746C_E/E_E ..........+150°C MAX746MJE........+175°C Storage Temperature Range .....-65°C to +160°C Lead Temperature (soldering, 10sec) .....+300°C
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.
ELECTRICAL CHARACTERISTICS
(V+ = 10V, ILOAD = 0A, IREF = 0µA, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER Input Voltage Output Voltage SYMBOL V+ VOUT V+ = 6V to 15V, 0V < (V+ - CS) < 0.125V, FB = 0V (includes line and load regulation) (V+ - CS) = 0V, external feedback mode V+ = 6V to 15V, FB = 0V V+ = 4V to 15V, external feedback mode 0V < (V+ - CS) < 0.125V Circuit of Figure 1, ILOAD = 0.5A to 2.5A, V+ = 6V VOUT = 5V For dual-mode switchover FB = 2V VREF IREF = 0µA IREF = 0µA to 100µA SS = 0V SS = 2V Operating, V+ = 15V Supply Current (Note 2) ISUPP Operating, V+ = 10V Shutdown mode Oscillator Frequency fOSC MAX746C MAX746E/M 85 80 MAX746C MAX746E/M 0.95 1.4 100 100 20 115 120 µA kHz 0.5 100 MAX746C MAX746E/M 1.97 1.96 1 2.00 2.00 9 1.0 500 1.1 1.4 1.7 mA 1.3 94 50 80 40 100 2.03 2.04 20 1.5 MAX746C MAX746E/M CONDITIONS MIN 4 4.85 1.96 1.95 5.08 2.00 2.00 0.05 0.1 2.5 TYP MAX 15 5.25 2.04 2.05 UNITS V V
Feedback Voltage
VFB
V
Line Regulation Load Regulation Efficiency OUT Leakage Current FB Input Logic Low FB Input Leakage Current Reference Voltage Reference Load Regulation Soft-Start Source Current Soft-Start Fault Current (Note 1)
%/V % % µA mV nA V mV µA µA
2
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High-Efficiency, PWM, Step-Down, N-Channel DC-DC Controller MAX746
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 10V, ILOAD = 0A, IREF = 0µA, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER Maximum Duty Cycle Charge-Pump Output Voltage Current-Sense Amplifier Current-Limit Threshold EXT Output High EXT Output Low EXT Sink Current EXT Source Current Compensation Pin Impedance MAX746C LBI Threshold Voltage LBO Output Voltage Low LBI Input Leakage Current LBO Output Leakage Current SHDN Input Voltage Low SHDN Input Voltage High SHDN Input Leakage Current Note 1: Note 2: VIL VIH SHDN = 10V 2.0 0.1 100 VOL LBI falling MAX746E/M ISINK = 0.5mA LBI = 2.5V V+ = 15V, LBO = 15V, LBI = 2.5V 1.96 2.00 2.04 0.4 100 1 0.4 V nA µA V V nA 1.97 VHIGH VLIMIT SYMBOL V+ = 6V IHIGH = 0mA to 10mA V+ CS VHIGH forced to 15V, IEXT = -1mA VHIGH forced to 15V, IEXT = 1mA VHIGH = 15V, VEXT = 12.5V VHIGH = 15V, VEXT = 2.5V 160 270 24 2.00 2.03 V CONDITIONS MIN 91 V+ + 4 125 VHIGH - 0.1 0.25 TYP 96 V+ + 5 V+ + 6 150 175 MAX UNITS % V mV V V mA mA k
The soft-start fault current is the current sink capability of SS when VREF < 1V or when the device is in shutdown. ISUPP is the supply current drawn by V+, which includes the current drawn by the charge pump. The charge pump doubles the current drawn by HIGH from the V+ input, so ISUPP = IV+ + 2IHIGH.
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