LT1109
Micropower Low Cost
DC/DC Converter
Adjustable and Fixed 5V, 12V
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DESCRIPTIO
EATURE
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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 IQ
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.
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PPLICATI
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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
U
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TYPICAL APPLICATI
All Surface Mount
Output Voltage
Flash Memory Program Output
Flash Memory VPP Generator
15
12
9
✝
ꢀ
L1
MBRS120T3
VOUT
ꢀ
V
= 5V
IN
33µH
5V/DIV
ꢀ
3
OV
SW
V
OUT
1
7
8
V
12V
V
SENSE
IN
IN
SHUTDOWN
5V/DIV
5V
80mA
LT1109CS8-12
6
+
C1**
1ms/DIV
SHUTDOWN*
GND
LT1109 • TA02
22µF
16V
3
4
SHUTDOWN
PROGRAM
0
LT1109 • TA01
* 8-PIN PACKAGE ONLY
0
10 20 30 40 50 60 70 80 90 100
✝
L1 = SUMIDA CD54-330LC (I
= 80mA)
OUT
COILTRONICS CTX33-1 (80mA)
OUTPUT CURRENT (mA)
LT1109 • TPC01
MURATA-ERIE L=Q5H04mN3A3)0K (I
OUT
= 50mA)
ISI LCS2414-330K (I
**C1 = MATSUO 267M1602226 OR EQUIVALENT
OUT
1
Linear [ Linear ]
