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LTC3872

3872fa

PI FU CTIO S

IPRG (Pin 1/Pin 4): Current Sense Limit Select Pin.

ITH (Pin 2/Pin 3): It serves as the error ampliﬁer com-

pensation point. Nominal voltage range for this pin is

0.7V to 1.9V.

VFB (Pin 3/Pin 2): Receives the feedback voltage from an

external resistor divider across the output.

GND (Pin 4/Pin 1): Ground Pin.

NGATE (Pin 5/Pin 8): Gate Drive for the External N-Channel

MOSFET. This pin swings from 0V to VIN.

VIN (Pin 6/Pin 7): Supply Pin. This pin must be closely

decoupled to GND (Pin 4).

RUN/SS (Pin 7/Pin 6): Shutdown and external soft-start

pin. In shutdown, all functions are disabled and the NGATE

pin is held low.

SW (Pin 8/Pin 5): Switch node connection to inductor and

current sense input pin through external slope compensa-

tion resistor. Normally, the external N-channel MOSFET’s

drain is connected to this pin.

Exposed Pad (NA/Pin 9): Ground. Must be soldered to PCB

for electrical contact and rated thermal performance.

(TS8/DD8)

RUN/SS

VIN

GND

ITH

VFB

NGATE

3872 FD

IPRG

SLOPE

COMPENSATION

550kHz

OSCILLATOR

CURRENT

COMPARATOR

VIN

VOLTAGE

REFERENCE

UNDERVOLTAGE

LOCKOUT

–

ITH

BUFFER

SWITCHING

LOGIC CIRCUIT

CURRENT LIMIT

CLAMP

INTERNAL

SOFT-START

RAMP

–+

ILIM

LATCH

1.2V

SHUTDOWN

COMPARATOR

SHDN

ERROR

AMPLIFIER

0.7

μA

FUNCTIONAL DIAGRAM

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