LTC4232 datasheet(6/16 Pages) LINER

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LTC4232

4232fb

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PIN FUNCTIONS

FB: Foldback and Power Good Input. Connect this pin to

an external resistive divider from OUT. If the voltage falls

below 0.6V, the current limit is reduced using a foldback

profile (see the Typical Performance Characteristics sec-

tion). If the voltage falls below 1.21V, the PG pin will pull

low to indicate the power is bad.

FLT: Overcurrent Fault Indicator. Open-drain output pulls

low when an overcurrent fault has occurred and the circuit

breaker trips. For overcurrent auto-retry tie to UV pin (see

the Applications Information section for details).

GATE: Gate Drive for Internal N-channel MOSFET. An

internal 24µA current source charges the gate of the

N-channel MOSFET. At start-up the GATE pin ramps up at

a 0.3V/ms rate determined by internal circuitry. During an

undervoltage or overvoltage condition a 250µA pull-down

current turns the MOSFET off. During a short-circuit or

undervoltage lockout condition, a 140mA pull-down cur-

rent source between GATE and OUT is activated.

GND: Device Ground.

IMON: Current Monitor Output. The current in the internal

MOSFETswitchisdividedby50,000andsourcedfromthis

pin. Placing a 20k resistor from this pin to GND creates a

0Vto2Vvoltageswingwhencurrentrangesfrom0Ato5A.

INTVCC: Internal 3.1V Supply Decoupling Output. This pin

must have a 1µF or larger bypass capacitor.

ISET:CurrentLimitAdjustmentPin.Fora5.6Acurrentlimit

value open this pin. This pin is driven by a 20k resistor

in series with a voltage source. The pin voltage is used

to generate the current limit threshold. The internal 20k

resistor and an external resistor between ISET and ground

create an attenuator that lowers the current limit value.

Due to circuit tolerance, the ISET resistor should not be

less than 2k. In order to match the temperature variation

of the sense resistor, the voltage on this pin increases at

the same rate as the sense resistance increases. Therefore

the voltage at ISET pin is proportional to temperature of

the MOSFET switch.

OUT: Output of Internal MOSFET Switch. Connect this pin

directly to the load.

OV: Overvoltage Comparator Input. Connect this pin to an

external resistive divider from VDD. If the voltage at this

pin rises above 1.235V, an overvoltage is detected and

the switch turns off. Tie to GND if unused.

PG: Power Good Indicator. Open-drain output pulls low

when the FB pin drops below 1.21V indicating the power is

bad. If the FB pin rises above 1.23V and the GATE to OUT

voltage exceeds 4.2V, the open-drain pull-down releases

the PG pin to go high.

SENSE: Current Sense Node and MOSFET Drain. The cur-

rent limit circuit controls the GATE pin to limit the sense

voltage between the VDD and SENSE pins to 42mV (5.6A)

orlessdependingonthevoltageattheFBpin.Theexposed

pad on DHC packages are connected to SENSE and must

be soldered to an electrically isolated printed circuit board

trace to properly transfer the heat out of the package.

TIMER: Timer Input. Connect a capacitor between this pin

and ground to set a 12ms/µF duration for current limit

before the switch is turned off. If the UV pin is toggled

low while the MOSFET switch is off, the switch will turn

on again following a cooldown time of 518ms/µF duration.

Tie this pin to INTVCC for a fixed 2ms overcurrent delay

and 100ms auto-retry time.

UV: Undervoltage Comparator Input. Tie high if unused.

Connect this pin to an external resistive divider from VDD.

If the UV pin voltage falls below 1.15V, an undervoltage is

detected and the switch turns off. Pulling this pin below

0.62V resets the overcurrent fault and allows the switch

to turn back on (see the Applications Information section

for details). If overcurrent auto-retry is desired then tie

this pin to the FLT pin.

VDD: Supply Voltage and Current Sense Input. This pin

has an undervoltage lockout threshold of 2.73V.

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