LT1109
1
Micropower Low Cost
DC/DC Converter
Adjustable and Fixed 5V, 12V
All Surface Mount
Flash Memory VPP Generator
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Flash Memory VPP Generators
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3V to 5V Converters
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5V to 12V Converters
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Disk Drives
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PC Plug-In Cards
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Peripherals
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Battery-Powered Equipment
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Uses Off-the-Shelf Inductors
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Only 33µH Inductor Required
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Low Cost
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3-Lead TO-92, SO8, or 8-Pin DIP
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Adjustable or Fixed 5V or 12V Output
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120kHz Oscillator
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Only Three External Components Required
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320µA I
Q
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1.6V Minimum Start-Up Voltage
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Logic Controlled Shutdown
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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.
SHUTDOWN
5V/DIV
OV
V
OUT
5V/DIV
1ms/DIV
LT1109 • TA02
L1
LT1109 • TA01
+
GND
SW
SENSE
LT1109CS8-12
V
OUT
12V
80mA
MBRS120T3
V
IN
V
IN
5V
SHUTDOWN PROGRAM
SHUTDOWN*
* 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
✝
✝
33µH
1
7
3
8
C1**
22µF
16V
4
Flash Memory Program Output
OUTPUT CURRENT (mA)
0
0
OUTPUT VOLTAGE (V)
3
6
9
12
15
10 100
LT1109 • TPC01
20 30 40 50 60 70 80 90
V
IN
= 5V
Output Voltage