MAX747 Datasheet, PDF (1/12 Pages) Maxim Integrated Products – High-Efficiency PWM, Step-Down P-Channel DC-DC Controller

19-0171; Rev 1; 9/93
High-Efficiency PWM, Step-Down
P-Channel DC-DC Controller
_______________General Description
The MAX747 high-efficiency, high-current, step-down
controller drives external P-channel FETs. It provides
90% to 95% efficiency from a 6V supply with load
currents ranging from 50mA up to 2.5A. It uses a
pulse-width-modulating (PWM) current-mode control
scheme to provide precise output regulation and low
output noise. The MAX747’s 4V to 15V input voltage
range, a fixed 5V/adjustable (Dual-Mode™) output, and
a current limit set with an external resistor make this
device ideal for a wide range of applications.
High efficiency is maintained with light loads due to a
proprietary dual-control (Idle-Mode™) scheme that
minimizes switching losses by reducing the switching
frequency at light loads. The low 800µA quiescent
current and ultra-low 0.6µA shutdown current further
extend battery life.
External components are protected by the MAX747’s
cycle-by-cycle current limit. The MAX747 also features a
2V ±1.5% reference, a comparator for low-battery
detection or level translating, as well as soft-start and
shutdown capability.
The MAX746, discussed in a separate data sheet,
functions similarly to the MAX747, but it drives N-channel
logic level FETs on the high side.
________________________Applications
Notebook Power Supplies
Personal Digital Assistants
Battery-Operated Equipment
Cellular Phones
5V to 3.3V Green PC Applications
__________________Pin Configuration
TOP VIEW
LBI 1
SS 2
REF 3
SHDN 4
FB 5
CC 6
AV+ 7
MAX747
14 ^LBO
13 GND
12 V+
11 EXT
10 ^AGND
9 CS
8 ^OUT
____________________________Features
o 90% to 95% Efficiency for 50mA to 2.5A
Output Currents
o 4V to 15V Input Voltage Range
o Low 800µA Supply Current
o 0.6µA Shutdown Current
o Drives External P-Channel FETs
o Cycle-by-Cycle Current Limiting
o 2V ±1.5% Accurate Reference Output
o Adjustable Soft-Start
o Precision Comparator for Power-Fail or
Low-Battery Warning
______________Ordering Information
PART
TEMP. RANGE
MAX747CPD
0°C to +70°C
MAX747CSD
0°C to +70°C
MAX747C/D
0°C to +70°C
MAX747EPD
-40°C to +85°C
MAX747ESD
-40°C to +85°C
MAX747MJD
-55°C to +125°C
* Contact factory for dice specifications.
PIN-PACKAGE
14 Plastic DIP
14 Narrow SO
Dice*
14 Plastic DIP
14 Narrow SO
14 CERIDIP
__________Typical Operating Circuit
INPUT
6V TO 15V
100µF
V+
AV+
MAX747 _CS
ON/OFF
SHDN
EXT
5OmΩ
P ^5OµH
OUTPUT
5V
2.3A
LOW-BATTERY
DETECTOR
INPUT
OUT
LBI
REF
LBO
SS CC FB AGND GND
0.1µF
LOW-BATTERY
DETECTOR
OUTPUT
430µF
DIP/SO
™ Dual-Mode and Idle-Mode are trademarks of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
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