19-0165; Rev 2; 1/96
5V, Step-Down,
Current-Mode PWM DC-DC Converters
__________________General Description
The MAX730A/MAX738A/MAX744A are 5V-output
CMOS, step-down switching regulators. The MAX738A/
MAX744A accept inputs from 6V to 16V and deliver
750mA. The MAX744A guarantees 500mA load capa-
bility for inputs above 6V and has tighter oscillator fre-
quency limits for low-noise (radio) applications. The
MAX730A accepts inputs between 5.2V and 11V and
delivers 450mA for inputs above 6V. Typical efficien-
cies are 85% to 96%. Quiescent supply current is
1.7mA and only 6µA in shutdown.
Pulse-width modulation (PWM) current-mode control
provides precise output regulation and excellent tran-
sient responses. Output voltage accuracy is guaran-
teed to be ±5% over line, load, and temperature varia-
tions. Fixed-frequency switching allows easy filtering of
output ripple and noise, as well as the use of small
external components. These regulators require only a
single inductor value to work in most applications, so
no inductor design is necessary.
The MAX730A/MAX738A/MAX744A also feature cycle-
by-cycle current limiting, overcurrent limiting, undervolt-
age lockout, and programmable soft-start protection.
___________________________Applications
Portable Instruments
Cellular Phones and Radios
Personal Communicators
Distributed Power Systems
Computer Peripherals
__________Typical Operating Circuit
________________________________Features
o 750mA Load Currents (MAX738A/MAX744A)
o High-Frequency, Current-Mode PWM
o 159kHz to 212.5kHz Guaranteed Oscillator
Frequency Limits (MAX744A)
o 85% to 96% Efficiencies
o 1.7mA Quiescent Current
o 6µA Shutdown Supply Current
o Single Preselected Inductor Value,
No Component Design Required
o Overcurrent, Soft-Start, and Undervoltage
Lockout Protection
o Cycle-by-Cycle Current Limiting
o 8-Pin DIP/SO Packages (MAX730A)
_________________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX730ACPA
0°C to +70°C
8 Plastic DIP
MAX730ACSA
0°C to +70°C
8 SO
MAX730AC/D
0°C to +70°C
Dice*
MAX730AEPA -40°C to +85°C
8 Plastic DIP
MAX730AESA -40°C to +85°C
8 SO
MAX730AMJA -55°C to +125°C 8 CERDIP
Ordering Information continued at end of data sheet.
*Contact factory for dice specifications.
_________________Pin Configurations
INPUT
6V TO 16V
68µF
V+
LX
ON/OFF
MAX738A
MAX744A
SHDN
OUT
REF
SS
CC
GND
33µH
OUTPUT
5V
100µF
TOP VIEW
SHDN 1
REF 2
SS 3
CC 4
MAX730A
MAX738A
MAX744A
DIP
8 V+
7 LX
6 GND
5 OUT
Pin Configurations continued on last page.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
