LTC4232 datasheet(7/22 Pages) AD

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LTC4231

Rev. B

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PIN FUNCTIONS

GATE: Gate Drive for External N-Channel MOSFET. After

all start-up conditions are satisfied, a 10μA pull-up cur-

rent from the internal charge pump charges up ∆VGATE to

the high threshold voltage ∆VGATE(H) and then turns off.

The charge pump turns on again when ∆VGATE decays by

more than 0.7V or every 15ms, whichever comes first,

and recharges ∆VGATE to ∆VGATE(H). During GATE turn-

off, a 1mA pull-down current discharges GATE to GND.

During severe short circuits, a 130mA pull-down current

is activated to discharge GATE to SOURCE.

GND: Device Ground.

GNDSW: Switched GND. Connect this pin to an external

resistive network to monitor IN for overvoltage or under-

voltage (OV/UV). To reduce the power dissipated by this

resistive divider, the LTC4231 periodically samples IN by

connecting GNDSW to GND once every 10ms. Tie this pin

to GND if unused.

IN: Supply Voltage and Current Sense Input. This pin has

a nominal undervoltage lockout threshold of 2.3V.

SHDN: Shutdown Control Input. A logic high at SHDN

enables the LTC4231. GATE ramps up after a debounce

delay of 40ms. A logic low at SHDN activates a 1mA pull-

down current at GATE, discharging it to GND. Once GATE

< 1.2V, the LTC4231 enters a low current Shutdown.

Connect to IN if unused. When connected to IN, if IN goes

below ground, use a resistor to limit the current to ≤1mA.

OV: Overvoltage Comparator Input. Connect this pin to an

external resistive network to monitor IN for OV. This pin

connects internally to an overvoltage comparator with a

0.795V threshold. To reduce the power dissipated by this

resistive divider, the LTC4231 periodically samples IN by

connecting GNDSW to GND once every 10ms. Once an

OV is detected at IN, GATE and STATUS pull low. Tie this

pin to GND if unused.

SENSE: Current Sense Input. Connect to the output of

the current sense resistor. The circuit breaker comparator

and the analog current limit amplifier monitor the voltage

across the current sense resistor. During an overcurrent

fault when ∆VSENSE exceeds 50mV, the circuit breaker

comparator trips and triggers TIMER to ramp up. For

more severe overcurrent faults, the analog current limit

amplifier controls the gate of the external MOSFET to keep

∆VSENSE at 80mV. To disable the circuit breaker compara-

tor and analog current limit amplifier, connect this pin to

IN.

SOURCE: N-Channel MOSFET Source Connection.

Connect this pin to the source of the external MOSFET.

STATUS: Status Output. Open-drain output that goes high

impedance when ∆VGATE first exceeds ∆VGATE(H). The state

of the pin is latched and resets (pulls low) when SHDN

goes low, an UVLO occurs, an OV/UV is detected at IN or

an overcurrent fault sets the internal current fault latch.

This pin may be left open if unused.

TIMER: Timer Input. Connect a capacitor between this

pin and GND to set a 24ms/µF duration for overcurrent

before the internal current fault latch trips and turns off the

MOSFET. For the LTC4231-1 latchoff option, the MOSFET

remains off until the current fault latch is cleared by pull-

ing SHDN low or by cycling power. For the LTC4231-2

auto-retry option, the current fault latch is cleared auto-

matically and the GATE is ramped up after a 500ms delay.

UVH, UVL: Undervoltage Comparator Input. Connect

these pins to an external resistive network to monitor

IN for UV. These pins connect internally to an undervolt-

age comparator with a 0.795V threshold. The comparator

monitors UVH when GATE is low and UVL when GATE

is high to implement separate undervoltage turn-on and

undervoltage turn-off thresholds. To reduce the power

dissipated by this resistive divider, the LTC4231 periodi-

cally samples IN by connecting GNDSW to GND once

every 10ms. Once an UV is detected at these pins, GATE

and STATUS pull low. Tie both pins to IN if unused. When

connected to IN, for applications where IN goes below

ground, use a resistor to limit the current to ≤1mA.

Exposed Pad (QFN Package): The exposed pad may be

left open or connected to device ground.

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