Rainbow Electronics MAX747 - Manual

_______________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
____________________________Features
♦ 90% to 95% Efficiency for 50mA to 2.5A
Output Currents
♦ 4V to 15V Input Voltage Range
♦ Low 800µA Supply Current
♦ 0.6µA Shutdown Current
♦ Drives External P-Channel FETs
♦ Cycle-by-Cycle Current Limiting
♦ 2V ±1.5% Accurate Reference Output
♦ Adjustable Soft-Start
♦ Precision Comparator for Power-Fail or
Low-Battery Warning
______________Ordering Information
* Contact factory for dice specifications.
MAX747
High-Efficiency PWM, Step-Down
P-Channel DC-DC Controller
________________________________________________________________ Maxim Integrated Products 1
OUTPUT
5V
2.3A
INPUT
6V TO 15V
AV+
EXT
OUT
GND
430µF
REF
MAX747 CS
SHDN
ON/OFF
LBI
LOW-BATTERY
DETECTOR
INPUT
V+
LOW-BATTERY
DETECTOR
OUTPUT
AGND FB CC SS
LBO
5Om Ω
5O µ H P
0.1µF
100µF
__________________Pin Configuration
SS
1
2
3
4
14
13
12
11
GND
CC
FB
AV+
LBI
DIP/SO
TOP VIEW
MAX747
5
6
7
10
9
8 OUT
AGND
REF
SHDN
LBO
V+
EXT
CS
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.
19-0171; Rev 1; 9/93
PART TEMP. RANGE PIN-PACKAGE
MAX747CPD 0°C to +70°C 14 Plastic DIP
MAX747CSD 0°C to +70°C 14 Narrow SO
MAX747C/D 0°C to +70°C Dice*
MAX747EPD -40°C to +85°C 14 Plastic DIP
MAX747ESD -40°C to +85°C 14 Narrow SO
MAX747MJD -55°C to +125°C 14 CERIDIP
™ Dual-Mode and Idle-Mode are trademarks of Maxim Integrated Products.