19-0263; Rev 1; 7/95
NUAL
KIT MA
ATION
HEET
EVALU
DATA S
LLOWS
FO
12V or Adjustable, High-Efficiency,
Low I
Q
, Step-Up DC-DC Controller
____________________________Features
o
90% Efficiency for 30mA to 2A Load Currents
o
Up to 24W Output Power
o
110µA Max Supply Current
o
5µA Max Shutdown Current
o
2V to 16.5V Input Range
o
Preset 12V or Adjustable Output Voltage
o
Current-Limited PFM Control Scheme
o
Up to 300kHz Switching Frequency
o
Evaluation Kit Available
_______________General Description
The MAX1771 step-up switching controller provides
90% efficiency over a 30mA to 2A load. A unique cur-
rent-limited pulse-frequency-modulation (PFM) control
scheme gives this device the benefits of pulse-width-
modulation (PWM) converters (high efficiency at heavy
loads), while using less than 110µA of supply current (vs.
2mA to 10mA for PWM converters).
This controller uses miniature external components. Its
high switching frequency (up to 300kHz) allows sur-
face-mount magnetics of 5mm height and 9mm diame-
ter. It accepts input voltages from 2V to 16.5V. The
output voltage is preset at 12V, or can be adjusted
using two resistors.
The MAX1771 optimizes efficiency at low input voltages
and reduces noise by using a single 100mV current-limit
threshold under all load conditions. A family of similar
devices, the MAX770–MAX773, trades some full-load
efficiency for greater current-limit accuracy; they provide
a 200mV current limit at full load, and switch to 100mV
for light loads.
The MAX1771 drives an external N-channel MOSFET
switch, allowing it to power loads up to 24W. If less power
is required, use the MAX756/MAX757 or MAX761/MAX762
step-up switching regulators with on-board MOSFETs.
An evaluation kit is available. Order the MAX1771EVKIT-SO.
MAX1771
______________Ordering Information
PART
MAX1771CPA
MAX1771CSA
MAX1771C/D
MAX1771EPA
MAX1771ESA
MAX1771MJA
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
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
8 CERDIP**
________________________Applications
Positive LCD-Bias Generators
Flash Memory Programmers
High-Power RF Power-Amplifier Supply
Palmtops/Hand-Held Terminals
Battery-Powered Applications
Portable Communicators
* Contact factory for dice specifications.
** Contact factory for availability and processing to MIL-STD-883B.
__________________Pin Configuration
__________Typical Operating Circuit
TOP VIEW
INPUT
2V TO V
OUT
OUTPUT
12V
EXT
V+
1
2
8
CS
GND
AGND
REF
MAX1771
ON/OFF
SHDN
EXT
CS
N
MAX1771
7
6
5
FB
3
SHDN
4
REF
FB AGND GND
V+
DIP/SO
________________________________________________________________
Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
