LT1109
Micropower Low Cost
DC/DC Converter
Adjustable and Fixed 5V, 12V
FEATURES
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DESCRIPTIO
Uses Off-the-Shelf Inductors
Only 33µH Inductor Required
Low Cost
3-Lead TO-92, SO8, or 8-Pin DIP
Adjustable or Fixed 5V or 12V Output
120kHz Oscillator
Only Three External Components Required
320µA I
Q
1.6V Minimum Start-Up Voltage
Logic Controlled Shutdown
The LT1109 is a simple step-up DC/DC converter. Avail-
able in 8-pin SO, 3-lead TO-92 (fixed output only) or
miniDIP packages, the devices require only three external
components to construct a complete DC/DC converter.
Current drain is just 320µA at no load, making the device
ideal for cost-sensitive applications where standby cur-
rent must be kept to a minimum.
The LT1109-5 can deliver 5V at 100mA from a 3V input
and the LT1109-12 can deliver 12V at 60mA from a 5V
input. The 8-pin versions also feature a logic controlled
SHUTDOWN pin that turns off the oscillator when taken
low. The gated-oscillator design requires no frequency
compensation components. The high frequency 120kHz
oscillator permits the use of small surface mount induc-
tors and capacitors. For a 5V to 12V at 120mA converter,
see the LT1109A. Foa a 5V to 12V at 200mA converter
with 20µA shutdown current, see the LT1301.
APPLICATI
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Flash Memory VPP Generators
3V to 5V Converters
5V to 12V Converters
Disk Drives
PC Plug-In Cards
Peripherals
Battery-Powered Equipment
TYPICAL APPLICATI
L1
¦
33µH
3
V
IN
5V
1
SW
V
IN
SENSE
8
MBRS120T3
All Surface Mount
Flash Memory VPP Generator
15
Output Voltage
V
IN
= 5V
12
OUTPUT VOLTAGE (V)
V
OUT
12V
80mA
9
SHUTDOWN
5V/DIV
6
1ms/DIV
LT1109 • TA02
LT1109CS8-12
7
SHUTDOWN*
GND
4
SHUTDOWN
PROGRAM
LT1109 • TA01
+
C1**
22µF
16V
3
* 8-PIN PACKAGE ONLY
¦
L1 = SUMIDA CD54-330LC (I
OUT
= 80mA)
COILTRONICS CTX33-1 (80mA)
MURATA-ERIE LQH4N330K (I
OUT
= 50mA)
ISI LCS2414-330K (I
OUT
= 50mA)
**C1 = MATSUO 267M1602226 OR EQUIVALENT
0
0 10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
LT1109 • TPC01
U
Flash Memory Program Output
V
OUT
5V/DIV
OV
UO
UO
1
LINER [ LINEAR TECHNOLOGY ]
