LT3481 Datasheet, PDF (1/24 Pages) Linear Technology – 36V, 2A, 2.8MHz Step-Down Switching Regulator with 50μA Quiescent Current

LT3481
36V, 2A, 2.8MHz Step-Down
Switching Regulator with
50µA Quiescent Current
FEATURES
■ _{Wide Input Range: 3.6V to 34V Operating,}
36V Maximum
■ _{2A Maximum Output Current}
■ _{Low Ripple Burst Mode}^® _Operation
50μA I_Q at 12V_IN to 3.3V_OUT
Output Ripple < 15mV
■ _{Adjustable Switching Frequency: 300kHz to 2.8MHz}
■ _{Low Shutdown Current: IQ < 1μA}
■ _{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
APPLICATIONS
■ _{Automotive Battery Regulation}
■ _{Power for Portable Products}
■ _{Distributed Supply Regulation}
■ _{Industrial Supplies}
■ _{Wall Transformer Regulation}
DESCRIPTION
The LT^®3481 is an adjustable frequency (300kHz to 2.8MHz)
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
bias current from the output when V_OUT is above 3V.
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_OUT reaches 90% of the programmed
output voltage. The LT3481 is available in 10-Pin MSOP
and 3mm x 3mm DFN packages with exposed pads for
low thermal resistance.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
3.3V Step-Down Converter
V_IN
4.5V TO
34V
V_IN
BD
V_OUT
3.3V
2A
OFF ON
4.7μF
16.2k
330pF
60.4k
RUN/SS
BOOST
V_C
LT3481
SW
RT
PG
BIAS
GND
FB
0.47μF
4.7μH
324k
200k
22μF
3481 TA01
Efficiency
90
10000.0
80
1000.0
70
100.0
60
10.0
50
40
30
0.0001
1.0
V_IN = 12V
V_OUT = 3.3V _0.1
L = 4.7μ
F = 800 kHz
0.01
0.001 0.01 0.1
1
10
LOAD CURRENT (A)
3481 TA01b
3481fb
1