LT1111
Micropower
DC/DC Converter
Adjustable and Fixed 5V, 12V
FEATURES
DESCRIPTIO
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Operates at Supply Voltages from 2V to 30V
The LT 1111 is a versatile micropower DC/DC converter.
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Works with Surface Mount Inductors
The device requires only three external components to
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72kHz Oscillator
deliver a fixed output of 5V or 12V. Supply voltage ranges
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Only Three External Components Required
from 2V to 12V in step-up mode and to 30V in step-down
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Step-Up or Step-Down Mode
mode. The LT1111 functions equally well in step-up, step-
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Low-Battery Detector Comparator On-Chip
down, or inverting applications.
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User Adjustable Current Limit
The LT1111 oscillator is set at 72kHz, optimizing the
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Internal 1A Power Switch
device to work with off-the-shelf surface mount inductors.
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Fixed or Adjustable Output Voltage Versions
The device can deliver 5V at 100mA from a 3V input in
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Space Saving 8-Pin MiniDIP or SO-8 Package
step-up mode or 5V at 200mA from a 12V input in step-
U
down mode.
APPLICATIO S
Switch current limit can be programmed with a single
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3V to 5V, 5V to 12V Converters
resistor. An auxiliary open-collector gain block can be
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9V to 5V, 12V to 5V Converters
configured as a low-battery detector, linear post regulator,
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Remote Controls
undervoltage lock-out circuit, or error amplifier.
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Peripherals and Add-On Cards
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Battery Backup Supplies
For input sources of less than 2V use the LT1110.
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Uninterruptible Supplies
, LTC and LT are registered trademarks of Linear Technology Corporation
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Laptop and Palmtop Computers
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Cellular Telephones
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Portable Instruments
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Flash Memory VPP Generators
TYPICAL APPLICATIO
Typical Load Regulation
All Surface Mount 3V to 5V Step-Up Converter
6
SUMIDA
5
CD54-220M
MBRS120T3
22m H
5V
V = 2V 2.2 2.4 2.6 2.8 3V
3V INPUT IN
4
100mA
I
V 3
LIM IN
SW1
+ +
2
10 F*m LT1111CS8-5 33 Fm
SENSE
1
GND SW2
0
0 25 50 75 100 125 150 175 200
LOAD CURRENT (mA)
*OPTIONAL
LT1111 TA01
LT1111 TA02
1111fd
1
OUTPUT VOLTAGE (V)
U
ULT1111
(Note 1)
ABSOLUTEXAI U RATI GS
Supply Voltage (V ) ............................................... 36V Operating Temperature Range
IN
SW1 Pin Voltage (V ) ......................................... 50V LT1111C............................................... 0 C to 70 C
SW1
SW2 Pin Voltage (V ) ............................ 0.5V to V LT1111I ......................................... 40 C to 105 C
SW2 IN
Feedback Pin Voltage (LT1111) ............................. 5.5V LT1111M (OBSOLETE) ............. 55 C to 125 C
Switch Current ....................................................... 1.5A Storage Temperature Range ................ 65 C to 150 C
Maximum Power Dissipation ............................ 500mW Lead Temperature (Soldering, 10 sec)................. 300 C
PACKAGE/ORDER I FOR ATIO
TOP VIEW ORDER PART ORDER PART
NUMBER NUMBER
I 1 8 FB (SENSE)*
LIM
TOP VIEW
LT1111CS8
LT1111CN8
V 2 7 SET
IN
I 1 8 FB (SENSE)* LT1111CS8-5
LT1111CN8-5 LIM
SW1 3 A0
6
LT1111CN8-12 LT1111CS8-12
V 2 7 SET
IN
SW2 4 5 GND
LT1111IS8
SW1 A0
3 6
N8 PACKAGE
SW2 GND
4 5
8-LEAD PLASTIC DIP
S8 PART MARKING
*FIXED VERSIONS
S8 PACKAGE
1111
T = 90 C, q = 130 C/W (N)
JMAX JA 8-LEAD PLASTIC SO
*FIXED VERSION 11115
J8 PACKAGE
LT1111MJ8
8-LEAD CERAMIC DIP 11111
T = 90 C, q = 150 C/W
JMAX JA
T = 150 C, q = 120 C/W (J) LT1111MJ8-5
JMAX JA
1111I
LT1111MJ8-12
OBSOLETE PACKAGE
Consider the N8 Package for Alternate Source
Consult LTC Marketing for parts specified with wider operating temperature ranges.
LECTR AL CHARACTERIST
E IC ICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25 C.V = 3V, Military or Commercial Version
A IN
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I Quiescent Current Switch OFF 300 400 m A
Q
V Input Voltage Step-Up Mode l 2.0 12.6 V
IN
Step-Down Mode l 30.0 V
Comparator Trip Point Voltage LT1111 (Note 2) l 1.20 1.25 1.30 V
V Output Sense Voltage LT1111-5 (Note 3 l 4.75 5.00 5.25 V
OUT
LT1111-12 (Note 3) l 11.40 12.00 12.60 V
Comparator Hysteresis LT1111 l 8 12.5 mV
Output Hysteresis LT1111-5 l 32 50 mV
LT1111-12 l 75 120 mV
f Oscillator Frequency 54 72 88 kHz
OSC
DC Duty Cycle: Step-Up Mode Full Load 43 50 59 %
Step-Down Mode 24 34 50 %
t Switch ON Time: Step-Up Mode I Tied to V 579 m s
ON LIM IN
Step-Down Mode V , = 5V, V = 12V 3.3 5 7.8 m s
OUT IN
V SW Saturation Voltage, Step-Up Mode V = 3.0V, I = 650mA 0.5 0.65 V
SAT IN SW
V = 5.0V, I = 1A 0.8 1.0 V
IN SW
SW Saturation Voltage, Step-Down Mode V = 12V, I = 650mA 1.1 1.5 V
IN SW
1111fd
2
U WU
U W W W