LT3957_15 Datasheet, PDF (1/28 Pages) Linear Technology – Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch

FEATURES
n _{Wide Input Voltage Range: 3V to 40V}
n _{Single Feedback Pin for Positive or Negative}
Output Voltage
n _{Internal 5A/40V Power Switch}
n _{Current Mode Control Provides Excellent Transient}
Response
n _{Programmable Operating Frequency (100kHz to}
1MHz) with One External Resistor
n _{Synchronizable to an External Clock}
n _{Low Shutdown Current < 1μA}
n _{Internal 5.2V Low Dropout Voltage Regulator}
n _{Programmable Input Undervoltage Lockout with}
Hysteresis
n _{Programmable Soft-Start}
n _{Thermally Enhanced QFN (5mm × 6mm) Package}
APPLICATIONS
n _Automotive
n _Telecom
n _Industrial
LT3957
Boost, Flyback, SEPIC and
Inverting Converter
with 5A, 40V Switch
DESCRIPTION
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 configured as either
a boost, flyback, 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 fixed 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.
TYPICAL APPLICATION
V_IN
4.5V TO 16V
High Efficiency Output Boost Converter
10μH
10μF
200k
V_IN
SW
EN/UVLO
GND
95.3k
LT3957
SGND
SENSE1
SYNC
SENSE2
FBX
RT SS
VC INTV_CC
41.2k
300kHz
0.33μF ^6.8k
4.7μF
22nF
10μF
s2
V_OUT
24V
600mA
226k
15.8k
3957 TA01a
Efficiency vs Output Current
100
V_IN = 12V
95
90
85
80
75
70
0
100 200 300 400 500 600
OUTPUT CURRENT (mA)
3957 TA01b
3957f
1