LT3681 Datasheet, PDF (1/24 Pages) Linear Technology – 36V, 2A, 2.8MHz Step-Down Switching Regulator with Integrated Power Schottky Diode

LT3681
36V, 2A, 2.8MHz Step-Down
Switching Regulator with
Integrated Power Schottky Diode
FEATURES
■ _{Wide Input Voltage 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_P-P
■ _{Adjustable Switching Frequency: 300kHz to 2.8MHz}
■ _{Low Shutdown Current: IQ < 1µA}
■ _{Integrated Boost Diode}
■ _{Integrated Power Schottky 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}
■ _{Small 14-Pin Thermally Enhanced}
(4mm x 3mm) DFN Package
U
APPLICATIO S
■ _{Automotive Battery Regulation}
■ _{Power for Portable Products}
■ _{Distributed Supply Regulation}
■ _{Industrial Supplies}
■ _{Wall Transformer Regulation}
DESCRIPTIO
The LT^®3681 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. An undedicated power Schottky diode is
integrated into the LT3681 to minimize the solution size.
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 LT3681 can further 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 LT3681
is available in 14-Pin 4mm x 3mm DFN package with
exposed pads for low thermal resistance.
, 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.
TYPICAL APPLICATIO
5V Step-Down Converter
V_IN
6.3V TO
34V
4.7mF
OFF ON
20k
330pF
60.4k
V_IN
RUN/SS
BD
BOOST
V_C LT3681
SW
DC
RT
DA
PG
BIAS
GND
FB
0.47mF _L
6.8mH
V_OUT
5V
2A
590k
200k
22mF
L: NEC PLC-0745-6R8
3681 TA01
Efficiency
100
90
80
70
60
50
40
30
20
10
0
0.0001 0.001
10.0000
1.0000
0.1000
0.0100
0.01 0.1
I_LOAD (A)
V_IN = 12V
V_OUT = 3.3V
L = 4.7mH
0.0010
F = 800 kHz
0.0001
1
10
3681 TA01b
3681f
1