LT1111
Micropower
DC/DC Converter
Adjustable and Fixed 5V, 12V
FEATURES
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DESCRIPTIO
Operates at Supply Voltages from 2V to 30V
72kHz Oscillator
Works with Surface Mount Inductors
Only Three External Components Required
Step-Up or Step-Down Mode
Low-Battery Detector Comparator On-Chip
User Adjustable Current Limit
Internal 1A Power Switch
Fixed or Adjustable Output Voltage Versions
Space Saving 8-Pin MiniDIP or SO-8 Package
The LT1111 is a versatile micropower DC/DC converter.
The device requires only three external components to
deliver a fixed output of 5V or 12V. Supply voltage ranges
from 2V to 12V in step-up mode and to 30V in step-down
mode. The LT1111 functions equally well in step-up, step-
down, or inverting applications.
The LT1111 oscillator is set at 72kHz, optimizing the
device to work with off-the-shelf surface mount inductors.
The device can deliver 5V at 100mA from a 3V input in
step-up mode or 5V at 200mA from a 12V input in step-
down mode.
Switch current limit can be programmed with a single
resistor. An auxiliary open-collector gain block can be
configured as a low-battery detector, linear post regulator,
undervoltage lock-out circuit, or error amplifier.
For input sources of less than 2V use the LT1110.
APPLICATI
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3V to 5V, 5V to 12V Converters
9V to 5V, 12V to 5V Converters
Remote Controls
Peripherals and Add-On Cards
Battery Backup Supplies
Uninterruptible Supplies
Laptop and Palmtop Computers
Cellular Telephones
Portable Instruments
Flash Memory VPP Generators
TYPICAL APPLICATI
Typical Load Regulation
6
5
OUTPUT VOLTAGE (V)
All Surface Mount 3V to 5V Step-Up Converter
SUMIDA
CD54-220M
MBRS120T3
22µH
3V INPUT
5V
100mA
4
3
2
1
0
0
25
V
IN
= 2V 2.2 2.4
I
LIM
+
V
IN
SW1
10
µ
F*
+
LT1111CS8-5
SENSE
GND
SW2
33
µ
F
*OPTIONAL
LT1111 • TA01
U
2.6
2.8 3V
50
75
100 125
150 175 200
LT1111 • TA02
UO
UO
LOAD CURRENT (mA)
1
LINER [ LINEAR TECHNOLOGY ]
