LTC4449 datasheet(6/14 Pages) LINER

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LTC4449

4449fa

BLOCK DIAGRAM

PIN FUNCTIONS

TG (Pin 1): High Side Gate Driver Output (Top Gate). This

pin swings between TS and BOOST.

TS (Pin 2): High Side MOSFET Source Connection (Top

Source).

BG (Pin 3): Low Side Gate Driver Output (Bottom Gate).

This pin swings between VCC and GND.

GND (Pin 4, Exposed Pad Pin 9): Chip Ground. The

exposed pad must be soldered to PCB ground for optimal

electrical and thermal performance.

IN (Pin 5): Input Signal. Input referenced to an internal

supply baised off of VLOGIC (Pin 6) and GND. If this pin is

ﬂoating, an internal resistive divider triggers a shutdown

mode in which both BG (Pin 3) and TG (Pin 1) are pulled

low. Trace capacitance on this pin should be minimized

to keep the shutdown time low.

VLOGIC (Pin 6): Logic Supply. This pin powers the input

buffer and logic. Connect this pin to the power supply

of the controller that is driving IN (Pin 5) to match input

thresholds or to VCC (Pin 7) to simplify PCB routing.

VCC (Pin 7): Output Driver Supply. This pin powers the

low side gate driver output directly and the high side gate

driver output through an external Schottky diode connected

between this pin and BOOST. A low ESR ceramic bypass

capacitor should be tied between this pin and GND.

BOOST (Pin 8): High Side Bootstrapped Supply. An

external capacitor should be tied between this pin and TS

(Pin 2). Normally an external Schottky diode is connected

between VCC (Pin 7) and this pin. Voltage swing at this

pin is from VCC – VD to VIN + VCC – VD, where VD is the

forward voltage drop of the Schottky diode.

SHOOT-

THROUGH

PROTECTION

THREE-STATE

INPUT

BUFFER

LEVEL

SHIFTER

INTERNAL

SUPPLY

UNDERVOLTAGE

LOCKOUT

UNDERVOLTAGE

LOCKOUT

BOOST

4449 BD

VCC

VLOGIC

VCC

GND

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