LT3971-5_15 Datasheet, PDF (1/28 Pages) Linear Technology – 38V, 1.2A, 2MHz Step-Down Regulator with 2.8A Quiescent Current

FEATURES
n _{Ultralow Quiescent Current:}
2.8µA I_Q Regulating 12V_IN to 3.3V_OUT
n _{Fixed Output Voltages: 3.3V, 5V,}
2.1µA I_Q Regulating 12V_IN to 3.3V_OUT
n _{Low Ripple Burst Mode}^® _Operation:
Output Ripple < 15mV_P-P
n _{Wide Input Voltage Range: 4.3V to 38V}
n _{1.2A Maximum Output Current}
n _{Adjustable Switching Frequency: 200kHz to 2MHz}
n _{Synchronizable Between 250kHz to 2MHz}
n _{Fast Transient Response}
n _{Accurate 1V Enable Pin Threshold}
n _{Low Shutdown Current: IQ = 700nA}
n _{Power Good Flag}
n _{Soft-Start Capability}
n _{Internal Compensation}
n _{Output Voltage: 1.19V to 30V}
n _{Small Thermally Enhanced 10-Lead MSOP, 16-Lead}
MSOP and (3mm × 3mm) DFN Packages
APPLICATIONS
n _{Automotive Battery Regulation}
n _{Power for Portable Products}
n _{Industrial Supplies}
LT3971/LT3971-3.3/LT3971-5
38V, 1.2A, 2MHz
Step-Down Regulator with
2.8µA Quiescent Current
DESCRIPTION
The LT^®3971 is an adjustable frequency monolithic buck
switching regulator that accepts a wide input voltage range
up to 38V. Low quiescent current design consumes only
2.8µA of supply current while regulating with no load. Low
ripple Burst Mode operation maintains high efficiency at
low output currents while keeping the output ripple below
15mV in a typical application. An internally compensated
current mode topology is used for fast transient response
and good loop stability. A high efficiency 0.33Ω switch
is included on the die along with a boost Schottky diode
and the necessary oscillator, control and logic circuitry.
An accurate 1V threshold enable pin can be used to shut
down the LT3971, reducing the input supply current to
700nA. A capacitor on the SS pin provides a controlled
inrush current (soft-start). A power good flag signals
when V_OUT reaches 91% of the programmed output volt-
age. The LT3971 is available in small 10-lead MSOP and
3mm × 3mm DFN packages with exposed pads for low
thermal resistance. A 16-lead MSOP is also offered which
has enhanced pin-to-pin fault tolerance.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
V_IN
4.5V TO 38V
3.3V Step Down Converter
OFF ON EN
V_{IN BOOST}
4.7µF
PG
SW
SS _LT3971-3.3
RT
BD
49.9k
SYNC GND ^VOUT
f = 800kHz
0.47µF _4.7µH
22µF
V_OUT
3.3V
1.2A
3971 TA01
No Load Supply Current
3.0
OUTPUT IN REGULATION
2.5
LT3971-5
2.0
LT3971-3.3
1.5
1.0
5
10 15 20 25 30 35
INPUT VOLTAGE (V)
3971 TA01b
3971fd
1