Datasheet

LTC3721-1

sn37211 37211fs

FB (Pin 13/Pin 12): Error Amplifier Inverting Input. This is

the voltage feedback input for the LTC3721-1. The nomi-

nal regulation voltage at FB is 1.2V.

SS (Pin 14/Pin 13): Soft-Start/Restart Delay Circuitry

Timing Capacitor. A capacitor from SS to GND provides a

controlled ramp of the current command. During overload

conditions, SS is discharged to ground initiating a soft-

start cycle. SS charging current is approximately 13µA. SS

will charge up to approximately 5V in normal operation.

During a constant overload current fault, SS will oscillate

at a low frequency between approximately 0.5V and 4V.

DESCRIPTIO S

UVLO (Pin 15/Pin 14): Input to Program System Turn-On

and Turn-Off Voltages. The nominal threshold of the UVLO

comparator is 5.0V. UVLO is connected to the main DC

system feed through a resistor divider. When the UVLO

threshold is exceeded, the LTC3721-1 commences a soft-

start cycle and a 10µA (nominal) current is fed out of UVLO

to program the desired amount of system hysteresis. The

hysteresis level can be adjusted by changing the resis-

tance of the divider. UVLO can also be used to terminate

all switching by pulling UVLO down to less than 4V. An

open drain or collector switch can perform this function

without changing the system turn on or turn off voltages.

NC (Pin 2, Pin 3, Pin 16/Pin 7, Pin 16): Not Connected.

(GN Package/UF Package)

PROGRAMMABLE

DEAD-TIME

DRVA

DRVB

37211 TD01

CURRENT

SENSE

OR C

RAMP

PWM

COMPARATOR

(–)

TI I G DIAGRA

WUW