LTC1265-5_15 Datasheet, PDF (1/16 Pages) Linear Technology – 1.2A, High Efficiency Step-Down DC/DC Converter

LTC1265/LTC1265-3.3/LTC1265-5
1.2A, High Efficiency
Step-Down DC/DC Converter
FEATURES
s _{High Efficiency: Up to 95%}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{Internal 0.3Ω Power Switch (VIN = 10V)}
s _{Short-Circuit Protection}
s _{Low Dropout Operation: 100% Duty Cycle}
s _{Low-Battery Detector}
s _{Low 160µA Standby Current at Light Loads}
s _{Active-High Micropower Shutdown: IQ < 15µA}
s _{Peak Inductor Current Independent of Inductor Value}
s _{Available in 14-pin SO Package}
U
APPLICATIO S
s _{5V to 3.3V Conversion}
s _{Distributed Power Systems}
s _{Step-Down Converters}
s _{Inverting Converters}
s _{Memory Backup Supply}
s _{Portable Instruments}
s _{Battery-Powered Equipment}
s _{Cellular Telephones}
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
(V_IN =10V) allowing up to 1.2A of output current.
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
continuously maximizing the life of the battery source. The
LTC1265 incorporates automatic power saving Burst Mode
operation to reduce gate charge losses when the load
currents drop below the level required for continuous
operation.
The inductor current is user-programmable via an external
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.
TYPICAL APPLICATIO
V_IN
5.4V TO
12V
+ C_IN^{††â€} 
68µF
20V
0.1µF _{PWR VIN}
SHDN
V_IN
SW
1k
LTC1265-5
I_TH
PGND
3900pF
130pF
C_T
SENSE⁺
L1*
33µH
D1^†
R_SENSE**
0.1Ω
+
V_OUT
5V
1A
C_OUT^††
220µF
10V
1000pF
SENSE^–
SGND
* COILTRONICS CTX33-4
** IRC LRC2010-01-R100-J
† MBRS130LT3
†† AVX TPSE227K010
††† AVX TPSE686K020
LTC1265-FO1
Figure 1. High Efficiency Step-Down Converter
100
95
90
85
80
75
70
0.01
LTC1265-5 Efficiency
V_IN = 6V
V_IN = 9V
V_IN = 12V
L = 33µH
V_OUT = 5V
R_SENSE = 0.1Ω
C_T = 130pF
0.10
LOAD CURRENT (A)
1.00
LTC1265 TA01
1