LT3957
1
3957f
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Wide Input Voltage Range: 3V to 40V
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Single Feedback Pin for Positive or Negative
Output Voltage
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Internal 5A/40V Power Switch
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Current Mode Control Provides Excellent Transient
Response
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Programmable Operating Frequency (100kHz to
1MHz) with One External Resistor
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Synchronizable to an External Clock
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Low Shutdown Current < 1µA
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Internal 5.2V Low Dropout Voltage Regulator
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Programmable Input Undervoltage Lockout with
Hysteresis
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Programmable Soft-Start
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Thermally Enhanced QFN (5mm × 6mm) Package
TYPICAL APPLICATION
DESCRIPTION
Boost, Flyback, SEPIC and
Inverting Converter
with 5A, 40V Switch
The LT
®
3957 is a wide input range, current mode DC/DC
converter which is capable of generating either positive
or negative output voltages. It can be confi gured as either
a boost, fl yback, SEPIC or inverting converter. It features
an internal low side N-channel power MOSFET rated for
40V at 5A and driven from an internal regulated 5.2V
supply. The fi xed frequency, current-mode architecture
results in stable operation over a wide range of supply
and output voltages.
The operating frequency of LT3957 can be set with an
external resistor over a 100kHz to 1MHz range, and can
be synchronized to an external clock using the SYNC pin.
A minimum operating supply voltage of 3V, and a low
shutdown quiescent current of less than 1µA, make the
LT3957 ideally suited for battery-powered systems.
The LT3957 features soft-start and frequency foldback
functions to limit inductor current during start-up.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No R
SENSE
and ThinSOT are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Patents pending.
High Effi ciency Output Boost Converter
FEATURES
APPLICATIONS
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Automotive
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Telecom
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Industrial
Effi ciency vs Output Current
SENSE2
SENSE1
LT3957
10µH
V
IN
SW
GND
FBX
RT SS
INTV
CC
EN/UVLO
SYNC
SGND
95.3k
VC
3957 TA01a
200k
41.2k
300kHz
4.7µF
0.33µF
6.8k
22nF
226k
15.8k
10µF
s2
V
OUT
24V
600mA
V
IN
4.5V TO 16V
10µF
OUTPUT CURRENT (mA)
0
70
EFFICIENCY (%)
75
80
85
90
95
100
100 200 300
400 500
3957 TA01b
600
V
IN
= 12V