LT3572

5

3572fa

PIN FUNCTIONS

SW (Pin 1): Switch Node. This pin connects to the col-

lector of an internal NPN power switch.

bypassed with a capacitor.

SYNC (Pin 3): Synchronization Pin. This pin is used to

synchronize the internal oscillator to an external signal.

The synchronizing range is 15% above the free running

frequency set by the RT pin up to 2.5MHz. If not used,

this pin must be tied to GND.

RT (Pin 4): Frequency Set Pin. Place a resistor to GND

to set the internal frequency. The range of oscillation is

500kHz to 2.25MHz.

GND (Pins 5, 9, 20): Ground.

PWMB (Pin 6): Logic Input for the Driver. A high signal

on this input sets OUTB high and OUTB low.

PWMA (Pin 7): Logic Input for the Driver. A high signal

on this input sets OUTA high and OUTA low.

Input Supply for the Drivers.

SHDN (Pin 10): Shutdown Pin. Tie to 1.5V or more to

enable the switcher. Pull low to disable the switcher.

SHDNA (Pin 11): Shutdown Pin. Tie to 1.5V or more to

enable OUTA and OUTA. Pull low to place OUTA and OUTA

in a high impedance state.

SHDNB (Pin 12): Shutdown Pin. Tie to 1.5V or more to

enable OUTB and OUTB. Pull low to place OUTB and OUTB

in a high impedance state.

FB (Pin 13): Feedback Pin. The LT3572 regulates this pin

to 1.225V. Connect the feedback resistors to this pin to

set the output voltage for the switching regulator.

SS (Pin 14): Soft-Start Pin. Place a soft-start capacitor

here. A capacitor on the soft-start pin slowly ramps the

current limit of the part from 0A to 1.3A.

PGOOD (Pin 15): This pin is an open-drain output that

pulls low when the FB pin is within 95% of its regulation

value.

OUTB (Pin 16): The Output Driver. This node switches

OUTB (Pin 17): The Output Driver. This node switches

OUTA (Pin 18): The Output Driver. This node switches

OUTA (Pin 19): The Output Driver. This node switches

Exposed Pad (Pin 21): Ground. The Exposed Pad of the

package provides both electrical contact to ground and

good thermal contact to the printed circuit board. The

Exposed Pad must be soldered to the circuit board for

proper operation.