LTC4211 datasheet(7/22 Pages) LINER

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LTC4235

4235f

For more information www.linear.com/LTC4235

pin FuncTions

CPO1, CPO2: Charge Pump Output. Connect a capacitor

from CPO1 or CPO2 to the corresponding IN1 or IN2 pin.

The value of this capacitor is approximately 10x the gate

capacitance (CISS) of the external MOSFET for ideal diode

control. The charge stored on this capacitor is used to pull

up the ideal diode MOSFET gate during a fast turn-on.

Leavethispinopeniffastidealdiodeturn-onisnotneeded.

DGATE1, DGATE2: Ideal Diode MOSFET Gate Drive Out-

put. Connect this pin to the gate of an external N-channel

MOSFET for ideal diode control. An internal clamp limits

the gate voltage to 12V above and a diode voltage below

IN.Duringfastturn-on,a1.5Apull-upchargesDGATEfrom

CPO. During fast turn-off, a 1.5A pull-down discharges

DGATE to IN.

D2OFF: Control Input. A rising edge above 1.235V turns

off the external ideal diode MOSFET in the IN2 supply path

and a falling edge below 1.215V allows the MOSFET to be

turned on. Connect this pin to an external resistive divider

fromIN1tomakeIN1thehigherpriorityinputsupplywhen

IN1 and IN2 are equal.

EN: Enable Input. Ground this pin to enable Hot Swap

control. If this pin is pulled high, the Hot Swap MOSFET

is not allowed to turn on. A 10µA current source pulls

this pin up to a diode below INTVCC. Upon EN going low

when ON is high, there is a start-up delay of 100ms for

debounce, after which the fault is cleared.

FAULT: Overcurrent Fault Status Output. Output that pulls

low when the fault timer expires during an overcurrent

fault. Otherwise it is pulled high by a 10µA current source

to a diode below INTVCC. It may be pulled above INTVCC

using an external pull-up. Leave open if unused.

FTMR:FaultTimerCapacitorTerminal.Connectacapacitor

between this pin and ground to set a 12ms/µF duration

for current limit before the external Hot Swap MOSFET is

turned off. The duration of the off time is 8s/µF, resulting

in a 0.15% duty cycle.

GND: Device Ground.

HGATE: Hot Swap MOSFET Gate Drive Output. Connect

this pin to the gate of the external N-channel MOSFET for

HotSwapcontrol.Aninternal10µAcurrentsourcecharges

the MOSFET gate. An internal clamp limits the gate volt-

age to 12V above and a diode voltage below OUT. During

an undervoltage generated turn-off, a 2mA pull-down

discharges HGATE to ground. During an output short or

INTVCC undervoltage lockout, a fast 200mA pull-down

discharges HGATE to OUT.

IN1, IN2: Positive Supply Input and Ideal Diode MOSFET

Gate Drive Return. Connect this pin to the power input

side of the external ideal diode MOSFET. The 5V INTVCC

supply is generated from IN1, IN2 and OUT via an internal

diode-OR. The voltage sensed at this pin is used to control

DGATE. The gate fast pull-down current returns through

this pin when DGATE is discharged.

INTVCC: Internal 5V Supply Decoupling Output. This pin

must have a 0.1µF or larger capacitor to GND. An external

load of less than 500µA can be connected at this pin. An

undervoltage lockout threshold of 2.2V will turn off both

MOSFETs.

IMON: Current Sense Monitoring Output. This pin voltage

is proportional to the sense voltage across the current

sense resistor with a voltage gain of 100. An internal 20k

resistor is connected from this pin to ground.

ON: ON Control Input. A rising edge above 1.235V turns

on the external Hot Swap MOSFET and a falling edge below

1.155V turns it off. Connect this pin to an external resistive

divider from SENSE+ to monitor the supply undervoltage

condition. Pulling the ON pin below 0.6V resets the fault

latch after an overcurrent fault. Tie to INTVCC if unused.

OUT: Hot Swap MOSFET Gate Drive Return. Connect this

pintotheoutputsideoftheexternalMOSFET.Thegatefast

pull-down current returns through this pin when HGATE

is discharged. An internal resistive divider connected be-

tween this pin and GND is used for current limit foldback

and power good monitor for 12V operation. If the OUT

voltage falls below 10.33V, the PWRGD pin pulls high to

indicate the power is bad. If the voltage falls below 7.65V,

the output current limit is reduced.

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