LTC4221IGN datasheet(9/28 Pages) LINER

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LTC4221

4221f

PI FU CTIO S

FAULT (Pin 7): Fault Status Input/Output. FAULT is a

bidirectional pin. As an input, pulsing VFAULT < 0.816V will

set the FAULT latch and bring the LTC4221 into the fault

state. As an output, FAULT is pulled high by an internal

3.8µA pull-up under normal operating conditions. When

an overcurrent fault is detected by a SENSE pin or a

overvoltage fault detected by an FB pin, the FAULT latch is

set and the LTC4221 goes into the fault state. The FAULT

latch is reset by a UVLO or the ON1 pin being driven below

0.4V.

FILTER (Pin 8): Overcurrent Fault Timing Filter. The

FILTER pin requires an external capacitor to ground to

adjust the response time of the two slow comparators. The

FILTER pin can be left unconnected for a default slow

comparator response time of 15µs.

TIMER (Pin 9): Analog System Timer. The TIMER pin

requires an external capacitor to ground to generate

timing delay cycles during start-up. The LTC4221’s initial

and start-up timing cycles are controlled by CTIMERand the

internal current sources connected to the TIMER pin.

GND (Pin 10): Ground. Connect to a ground plane for

optimum performance.

PWRGD2 (Pin 11): Channel 2 Power Good Output. Similar

functionality as PWRGD1. Controlled by FB2.

FB2 (Pin 12): VOUT2 Feedback Input. Similar functionality

as FB1. Monitors channel 2 output voltage, controls

PWRGD2 output and channel 2 start-up current limit.

GATE2 (Pin 13): Channel 2 Gate Drive. Similar functional-

ity as GATE1. Controls the gate drive of the channel 2

external N-channel MOSFET. ON2 controls GATE2 in the

same manner as ON1 controls GATE1. VON1 < 0.4V over-

rides conditions at ON2 and GATE2 is held low by a 100µA

current source. UVLO, overvoltage, overcurrent and exter-

nally generated faults override conditions at ON1 and ON2,

and pull GATE2 low.

SENSE2 (Pin 14): Channel 2 Current Sense Input. Similar

functionality as SENSE1. Monitors channel 2 load current

through RSENSE2 placed in the supply path between VCC2

and SENSE2. To disable the current limit and circuit

breaker function for channel 2, tie SENSE2 to VCC2.

VCC2 (Pin 15): Channel 2 Positive Supply Input. VCC2 can

range from 1V to 13.5V for normal operation but it must

be ≤VCC1. An undervoltage lockout circuit disables both

channels whenever the voltage at VCC2 is less than 0.8V.

ON2 (Pin 16): Channel 2 On Input. GATE2 is pulled to

ground by a 100µA current source when VON2 < 0.821V.

When VON2 > 0.851V, GATE2 ramps up after an initial

timing cycle.

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