LT3680 Datasheet, PDF (1/24 Pages) Linear Technology – 36V, 3.5A, 2.4MHz Step-Down Switching Regulator with 75μA Quiescent Current

LT3680
36V, 3.5A, 2.4MHz
Step-Down Switching Regulator
with 75µA Quiescent Current
FEATURES
■ _{Wide Input Voltage Range: 3.6V to 36V}
■ _{3.5A Maximum Output Current}
■ _{Low Ripple (<15mVP-P) Burst Mode}^® _Operation:
I_Q = 75μA at 12V_IN to 3.3V_OUT
■ _{Adjustable Switching Frequency: 200kHz to 2.4MHz}
■ _{Low Shutdown Current: IQ < 1μA}
■ _{Integrated Boost Diode}
■ _{Synchronizable Between 250kHz to 2MHz}
■ _{Power Good Flag}
■ _{Saturating Switch Design: 95m On-Resistance}
■ _{0.790V Feedback Reference Voltage}
■ _{Output Voltage: 0.79V to 30V}
■ _{Thermal Protection}
■ _{Soft-Start Capability}
■ _{Small 10-Pin Thermally Enhanced MSOP and}
(3mm × 3mm) DFN Packages
APPLICATIONS
■ _{Automotive Battery Regulation}
■ _{Power for Portable Products}
■ _{Distributed Supply Regulation}
■ _{Industrial Supplies}
■ _{Wall Transformer Regulation}
DESCRIPTION
The LT^®3680 is an adjustable frequency (200kHz to
2.4MHz) monolithic buck switching regulator that accepts
input voltages up to 36V. A high efficiency 95m 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 LT3680 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
91% of the programmed output voltage. The LT3680 is
available in 10-Pin MSOP and 3mm × 3mm DFN packages
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 APPLICATION
5V Step-Down Converter
V_IN
6.3V TO 36V
OFF ON
V_IN
RUN/SS
BD
BOOST
15k
10μF
680pF
63.4k
V_C
LT3680
SW
RT
PG
SYNC
GND
FB
V_OUT
5V
3.5A
0.47μF _4.7μH
536k
100k
47μF
3680 TA01a
Efficiency
100
V_IN = 12V
90
V_IN = 34V
80
V_IN = 24V
70
60 _{VOUT = 5V}
L = 4.7μH
f = 600kHz
50
0 0.5 1 1.5 2 2.5
OUTPUT CURRENT (A)
3 3.5
3680 G01
3680fa
1