LT3481
36V, 2A, 2.8MHz Step-Down
Switching Regulator with
50µA Quiescent Current
FEATURES
DESCRIPTION
TheLT®3481isanadjustablefrequency(300kHzto2.8MHz)
monolithic buck switching regulator that accepts input
voltages up to 34V (36V maximum). A high efficiency
0.18Ω switch is included on the die along with a boost
Schottky diode and the necessary oscillator, control, and
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 LT3481 can fur-
ther enhance low output current efficiency by drawing
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Wide Input Range: 3.6V to 34V Operating,
36V Maximum
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2A Maximum Output Current
Low Ripple Burst Mode® Operation
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50μA I at 12V to 3.3V
Q
IN
OUT
Output Ripple < 15mV
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Adjustable Switching Frequency: 300kHz to 2.8MHz
Low Shutdown Current: I < 1μA
Q
Integrated Boost Diode
Power Good Flag
Saturating Switch Design: 0.18Ω On-Resistance
1.265V Feedback Reference Voltage
Output Voltage: 1.265V to 20V
Soft-Start Capability
Synchronizable Between 275kHz to 475kHz
Small 10-Pin Thermally Enhanced MSOP and
(3mm x 3mm) DFN Packages
bias current from the output when V
is above 3V.
OUT
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 90% of the programmed
OUT
output voltage. The LT3481 is available in 10-Pin MSOP
and 3mm x 3mm DFN packages with exposed pads for
low thermal resistance.
APPLICATIONS
, LT, LTC and LTM are registered trademarks 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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Power for Portable Products
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Distributed Supply Regulation
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Industrial Supplies
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Wall Transformer Regulation
TYPICAL APPLICATION
3.3V Step-Down Converter
Efficiency
V
V
3.3V
2A
90
80
70
60
50
10000.0
1000.0
100.0
10.0
IN
OUT
4.5V TO
34V
V
BD
IN
RUN/SS
BOOST
OFF ON
16.2k
0.47μF
4.7μH
V
C
SW
LT3481
GND
4.7μF
RT
PG
330pF
1.0
BIAS
FB
V
V
= 12V
IN
OUT
324k
= 3.3V
40
30
0.1
60.4k
L = 4.7μ
F = 800 kHz
200k
22μF
0.01
0.0001 0.001
0.01
0.1
1
10
LOAD CURRENT (A)
3481 TA01
3481 TA01b
3481fb
1