LTC1265/LTC1265-3.3/LTC1265-5
1.2A, High Efficiency
Step-Down DC/DC Converter
U
FEATURES
DESCRIPTIO
The LTC®1265 is a monolithic step-down current mode
DC/DC converter featuring Burst Mode TM operation at low
output current. The LTC1265 incorporates a 0.3Ω switch
(VIN =10V) allowing up to 1.2A of output current.
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High Efficiency: Up to 95%
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Current Mode Operation for Excellent Line and Load
Transient Response
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Internal 0.3
Ω Power Switch (VIN = 10V)
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Short-Circuit Protection
Under no load condition, the converter draws only 160µA.
In shutdown it typically draws a mere 5µA making this
converter ideal for current sensitive applications. In drop-
out the internal P-channel MOSFET switch is turned on
continuouslymaximizingthelifeofthebatterysource.The
LTC1265incorporatesautomaticpowersavingBurstMode
operation to reduce gate charge losses when the load
currents drop below the level required for continuous
operation.
Low Dropout Operation: 100% Duty Cycle
Low-Battery Detector
Low 160µA Standby Current at Light Loads
Active-High Micropower Shutdown: IQ < 15µA
Peak Inductor Current Independent of Inductor Value
Available in 14-pUin SO Package
APPLICATIO S
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5V to 3.3V Conversion
Theinductorcurrentisuser-programmableviaanexternal
current sense resistor. Operation up to 700kHz permits
the use of small surface mount inductors and capacitors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
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Distributed Power Systems
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Step-Down Converters
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Inverting Converters
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Memory Backup Supply
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Portable Instruments
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Battery-Powered Equipment
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Cellular Telephones
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TYPICAL APPLICATIO
V
IN
5.4V TO
12V
LTC1265-5 Efficiency
†††
+
C
IN
100
68µF
20V
0.1µF
L1*
R
**
SENSE
V
PWR V
SHDN
IN
IN
33µH
V
5V
1A
0.1Ω
OUT
V
= 6V
= 9V
IN
SW
95
90
85
80
75
70
V
D1†
IN
LTC1265-5
1k
††
+
C
OUT
I
TH
220µF
PGND
V
= 12V
IN
10V
3900pF
+
C
T
SENSE
130pF
1000pF
L = 33µH
V = 5V
OUT
–
SENSE
R
T
= 0.1Ω
* COILTRONICS CTX33-4
SENSE
SGND
C
= 130pF
** IRC LRC2010-01-R100-J
†
MBRS130LT3
†† AVX TPSE227K010
††† AVX TPSE686K020
0.01
0.10
LOAD CURRENT (A)
1.00
LTC1265-FO1
LTC1265 TA01
Figure 1. High Efficiency Step-Down Converter
1