LT3972
33V, 3.5A, 2.4MHz
Step-Down Switching Regulator
with 75µA Quiescent Current
FEATURES
DESCRIPTION
TheLT®3972isanadjustablefrequency(200kHzto2.4MHz)
monolithic buck switching regulator that accepts input
voltages up to 33V (62V Maximum). A high efficiency
95mΩ switch is included on the die along with a boost
Schottky diode and the necessary oscillator, control, and
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Wide Input Range:
Operation from 3.6V to 33V
Over-Voltage Lockout Protects Circuits
Through 62V Transients
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3.5A Maximum Output Current
Low Ripple (<15mV ) Burst Mode® Operation:
logic circuitry. Current mode topology is used for fast
transient response and good loop stability. Low ripple
Burst Mode operation maintains high efficiency at low
output currents while keeping output ripple below 15mV
in a typical application. In addition, the LT3972 can fur-
ther enhance low output current efficiency by drawing
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P-P
IN
I = 75μA at 12V to 3.3V
Q
OUT
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Adjustable Switching Frequency: 200kHz to 2.4MHz
Low Shutdown Current: I < 1μA
Integrated Boost Diode
Synchronizable Between 250kHz to 2MHz
Power Good Flag
Q
bias current from the output when V
is above 3V.
OUT
Saturating Switch Design: 95mΩ On-Resistance
Output Voltage: 0.79V to 30V
Thermal Protection
Soft-Start Capability
Small 10-Pin Thermally Enhanced MSOP and
(3mm × 3mm) DFN Packages
Shutdown reduces input supply current to less than 1μA
while a resistor and capacitor on the RUN/SS pin provide a
controlled output voltage ramp (soft-start). A power good
flag signals when V
reaches 91% of the programmed
OUT
output voltage. The LT3972 is available in 10-Pin MSOP
and 3mm × 3mm DFN packages with exposed pads for
low thermal resistance.
APPLICATIONS
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
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Automotive Battery Regulation
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Distributed Supply Regulation
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Industrial Supplies
Wall Transformer Regulation
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TYPICAL APPLICATION
5V Step-Down Converter
Efficiency
100
V
OUT
V
IN
5V
6.3V TO 33V
TRANSIENT
TO 62V
V
= 12V
3.5A
IN
90
80
70
60
50
V
BD
IN
V
= 30V
IN
RUN/SS
BOOST
OFF ON
V
= 24V
IN
0.47μF
4.7μH
536k
15k
V
C
SW
LT3972
GND
10μF
RT
680pF
PG
V
= 5V
OUT
L = 4.7μH
63.4k
SYNC
FB
f = 600kHz
100k
47μF
0
0.5
1
1.5
2
2.5
3.5
3
OUTPUT CURRENT (A)
3680 TA01a
3680 TA01
3972f
1