LT3972_15 Datasheet, PDF (1/24 Pages) Linear Technology – 33V, 3.5A, 2.4MHz Step-Down Switching Regulator with 75A Quiescent Current

LT3972
33V, 3.5A, 2.4MHz
Step-Down Switching Regulator
with 75µA Quiescent Current
FEATURES
■ _{Wide Input Range:}
Operation from 3.6V to 33V
Overvoltage Lockout Protects Circuits
Through 62V Transients
■ _{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: 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
APPLICATIONS
■ _{Automotive Battery Regulation}
■ _{Distributed Supply Regulation}
■ _{Industrial Supplies}
■ _{Wall Transformer Regulation}
DESCRIPTION
The LT^®3972 is an adjustable frequency (200kHz to 2.4MHz)
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
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
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 LT3972 is available in 10-pin MSOP
and 3mm × 3mm DFN packages with exposed pads for
low thermal resistance.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered
trademarks 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 33V
TRANSIENT
TO 62V
V_IN
BD
V_OUT
5V
3.5A
OFF ON
RUN/SS
BOOST
15k
10μF
680pF
63.4k
V_C
LT3972
SW
RT
PG
SYNC
GND
FB
0.47μF _4.7μH
536k
100k
47μF
3972 TA01
Efficiency
100
V_IN = 12V
90
V_IN = 30V
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
3972 TA01a
3972fa
1