MAX1771 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller

19-0263; Rev 1; 7/95
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12V or Adjustable, High-Efficiency,
Low I_Q, Step-Up DC-DC Controller
_______________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.
________________________Applications
Positive LCD-Bias Generators
Flash Memory Programmers
High-Power RF Power-Amplifier Supply
Palmtops/Hand-Held Terminals
Battery-Powered Applications
Portable Communicators
____________________________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
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX1771CPA
0°C to +70°C
8 Plastic DIP
MAX1771CSA
0°C to +70°C
8 SO
MAX1771C/D
MAX1771EPA
0°C to +70°C
-40°C to +85°C
Dice*
8 Plastic DIP
MAX1771ESA
MAX1771MJA
-40°C to +85°C
-55°C to +125°C
8 SO
8 CERDIP**
* Contact factory for dice specifications.
** Contact factory for availability and processing to MIL-STD-883B.
__________________Pin Configuration
__________Typical Operating Circuit
INPUT
2V TO VOUT
MAX1771 ^EXT
N
ON/OFF
SHDN
CS
REF
V+
FB AGND GND
OUTPUT
12V
TOP VIEW
EXT 1
V+ ²
FB ³
SHDN ⁴
MAX1771
DIP/SO
8 _CS
7 GND
6 AGND
5 _REF
________________________________________________________________ Maxim Integrated Products 1
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