Rainbow Electronics MAX746 - Manual

_______________General Description
The MAX746 is a high-efficiency, high-current, step-down
DC-DC power-supply controller that drives external N-chan-
nel 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-Mode
TM ) 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 propri-
etary automatic pulse-skipping control (Idle-Mode
TM ) scheme
that minimizes switching losses by reducing the switching fre-
quency 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 cycle-
by-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.
The MAX747—discussed in a separate data sheet—
functions similarly to the MAX746, but drives P-channel logic
level FETs.
________________________Applications
5V-to-3.3V Green PC Applications
Notebook/Laptop Computers
Personal Digital Assistants
Battery-Operated Equipment
Cellular Phones
____________________________Features
♦ 93% to 96% Efficiency for 50mA to 3A
Output Currents
♦ 4V to 15V Input Voltage Range
♦ Low 950µA Supply Current
♦ 1.4µA Shutdown Current
♦ Drives External N-Channel FETs
♦ Fixed-Frequency Current-Mode PWM (Heavy Loads)
♦ Idle-Mode PFM (Light Loads)
♦ Cycle-by-Cycle Current Limiting
♦ 2V ±1.5% Accurate Reference Output
♦ Adjustable Soft-Start
♦ Undervoltage Lockout
♦ Precision Comparator for Power-Fail or
Low-Battery Warning
______________Ordering Information
* Contact factory for dice specifications.
MAX746
High-Efficiency, PWM, Step-Down,
N-Channel DC-DC Controller
________________________________________________________________ Maxim Integrated Products 1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
GND
V+
CP
HIGH REF
SS
LBI
LBO
TOP VIEW
MAX746
EXT
AGND
CS
OUT AV+
CC
FB
SHDN
DIP/SO
__________________Pin Configuration
CP
HIGH
SHDN
LBI
REF
EXT
OUT
V+
AV+
CS
OUTPUT
5V
LOW-BATTERY
DETECTOR OUTPUT
LBO
GND AGND FB CC SS
ON/OFF
LOW-BATTERY
DETECTOR INPUT
INPUT 6V TO 15V
40m Ω
39 µ H
440 µ F
MAX746
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.
PART TEMP. RANGE PIN-PACKAGE
MAX746CPE 0°C to +70°C 16 Plastic DIP
MAX746CSE 0°C to +70°C 16 Narrow SO
MAX746C/D 0°C to +70°C Dice*
MAX746MJE -55°C to +125°C 16 CERDIP
MAX746ESE -40°C to +85°C 16 Narrow SO
MAX746EPE -40°C to +85°C 16 Plastic DIP
19-0192; Rev 1; 11/93
™Dual-Mode and Idle-Mode are trademarks of Maxim Integrated Products.