LT3991

1

3991f

TYPICAL APPLICATION

DESCRIPTION

55V, 1.2A Step-Down

Regulator with 2.8µA

Quiescent Current

switching regulator that accepts a wide input voltage range

up to 55V. 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 0.44Ω 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 LT3991, 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

age. The LT3991 is available in small 10-pin MSOP and

3mm

× 3mm DFN packages with exposed pads for low

thermal resistance.

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.

3.3V Step Down Converter

FEATURES

APPLICATIONS

and (3mm

× 3mm) DFN Packages

No Load Supply Current

SW

FB

SS

RT

4.3V TO 55V

3.3V

1.2A

4.7μF

0.47μF

47μF

1M

118k

10μH

1.78M

GND

BD

SYNC

OFF ON

10pF

LT3991

3991 TA01

EN

BOOST

PG

INPUT VOLTAGE (V)

5

1.0

15

25

35

45

55

3991 TA01b

2.0

1.5

4.0

3.5

3.0

2.5