NCP382

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7

FUNCTIONAL DESCRIPTION

Overview

The NCP382 is a dual high side power distribution

switches designed to protect the input supply voltage in case

of heavy capacitive loads, short circuit or over current. In

addition, the high side MOSFETs are turned off during

undervoltage or thermal shutdown condition. Thanks to the

soft start circuitry, NCP382 is able to limit large current and

voltage surges.

Overcurrent Protection

NCP382 switches into a constant current regulation mode

Depending on the load, the output voltage is decreased

accordingly.

− In case of hot plug with heavy capacitive load, the

output voltage is brought down to the capacitor voltage.

value until the charge of the capacitor is completed.

Drop due to

capacitor charge

Figure 6. Heavy Capacitive Load

value and the voltage value is reduced according to the

load by the following relation:

V

I

OCP

(eq. 1)

Figure 7. Overload

− In case of short circuit or huge load, the current is

short condition is removed. If the output remains

shorted or tied to a very low voltage, the junction

device enters in thermal shutdown (MOSFET is

turned−off).

Thermal

Regulation

Threshold

Timer

Regulation

Mode

Figure 8. Short−Circuit

Then, the device enters in timer regulation mode, described

in 2 phases:

the die temperature to drop.

.

The timer regulation mode allows the device to handle

high thermal dissipation (in case of short circuit for

example) within temperature operating condition.

NCP382 stays in on−phase/off−phase loop until the over

current condition is removed or enable pin is toggled.

Remark: other regulation modes can be available for

different applications. Please contact our On Semiconductor

representative for availability.

FLAG Indicator

The FLAG pin is an open−drain MOSFET asserted low

during overcurrent or overtemperature conditions. When an

overcurrent fault is detected on the power path, FLAG pin

is asserted low at the end of the associate deglitch time

(TFOCP). Thanks to this feature, the FLAG pin is not tied

low during the charge of a heavy capacitive load or a voltage

transient on output. The FLAG pin remains low until the

fault is removed. Then, the FLAG pin goes high at the end

Undervoltage Lock−out

Thanks to a built−in under voltage lockout (UVLO)

circuitry, the output remains disconnected from input until

hysteresis witch provides noise immunity to transient

condition.

Thermal Sense

Thermal shutdown turns off the power MOSFET if the die

part from turning on until the die temperature cools at

TRSD.