19-0113; Rev. 2; 1/95
NUAL
KIT MA
ATION
HEET
EVALU
DATA S
LOWS
FOL
3.3V/5V/Adjustable-Output,
Step-Up DC-DC Converters
____________________________Features
o
Operates Down to 0.7V Input Supply Voltage
o
87% Efficiency at 200mA
o
60µA Quiescent Current
o
20µA Shutdown Mode with Active Reference and
LBI Detector
o
500kHz Maximum Switching Frequency
o
±1.5% Reference Tolerance Over Temperature
o
Low-Battery Detector (LBI/LBO)
o
8-Pin DIP and SO Packages
_______________General Description
The MAX756/MAX757 are CMOS step-up DC-DC switch-
ing regulators for small, low input voltage or battery-pow-
ered systems. The MAX756 accepts a positive input
voltage down to 0.7V and converts it to a higher pin-
selectable output voltage of 3.3V or 5V. The MAX757 is
an adjustable version that accepts an input voltage down
to 0.7V and generates a higher adjustable output voltage
in the range from 2.7V to 5.5V. Typical full-load efficiencies
for the MAX756/MAX757 are greater than 87%.
The MAX756/MAX757 provide three improvements over
previous devices. Physical size is reduced—the high
switching frequencies (up to 0.5MHz) made possible by
MOSFET power transistors allow for tiny (<5mm diameter)
surface-mount magnetics. Efficiency is improved to 87%
(10% better than with low-voltage regulators fabricated in
bipolar technology). Supply current is reduced to 60µA
by CMOS construction and a unique constant-off-time
pulse-frequency modulation control scheme.
MAX756/MAX757
______________Ordering Information
PART
MAX756CPA
MAX756CSA
MAX756C/D
MAX756EPA
MAX756ESA
MAX757CPA
MAX757CSA
MAX757C/D
MAX757EPA
MAX757ESA
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
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
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
________________________Applications
3.3V to 5V Step-Up Conversion
Palmtop Computers
Portable Data-Collection Equipment
Personal Data Communicators/Computers
Medical Instrumentation
2-Cell & 3-Cell Battery-Operated Equipment
Glucose Meters
* Dice are tested at T
A
= +25°C only.
__________Typical Operating Circuit
INPUT
2V to V
OUT
_________________Pin Configurations
TOP VIEW
SHDN
1
2
8
7
LX
GND
OUT
LBI
150µF
5
1
LBI
SHDN
LX
8
OUTPUT
22µH
5V at 200mA
or
1N5817
3.3V at 300mA
100µF
3/5
REF
3
LBO
4
MAX756
6
5
DIP/SO
SHDN
FB
1
2
8
7
2
MAX756
3/5
OUT
6
LX
GND
OUT
LBI
3
0.1µF
REF
GND
7
LBO
4
LOW-BATTERY
DETECTOR OUTPUT
REF
3
LBO
4
MAX757
6
5
DIP/SO
________________________________________________________________
Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
