AP22652/AP22653/AP22652A/AP22653A

Document number: DS41186 Rev. 3 - 2

11 of 16

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September 2021

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AP22652/AP22653/AP22652A/AP22653A

Application Information (continued)

Special Functions

Discharge Function

When enable is de-asserted, or when the input voltage is under UVLO level, the discharge function is active. The output capacitor is discharged

through an internal NMOS that has a discharge resistance of 600Ω. Hence, the output voltage drops down to zero. The time taken for discharge is

dependent on the RC time constant of the resistance and the output capacitor.

FAULT Response

The FAULT open-drain output goes active low for any of following faults: overcurrent, OUT pin short-circuit, reverse-voltage condition, or thermal

shutdown. The time from when a fault condition is encountered to when the FAULT output goes low is 6ms (typ). The FAULT output remains low

until overcurrent, OUT pin short-circuit, and overtemperature conditions are removed. Connecting a heavy capacitive load to the output of the

device can cause a momentary overcurrent condition, which does not trigger the FAULT due to the 6ms deglitch timeout. This 6ms timeout is also

applicable for overcurrent recovery and overtemperature recovery. The AP22652 and AP22653 are designed to eliminate erroneous overcurrent

reporting without the need for external components, such as an RC delay network.

For the AP22652/52A and AP22653/53A when the reverse voltage condition is triggered, FAULT output goes low after 6ms (typ). This 6ms (typ)

timeout is also applicable for the recovery from reverse voltage fault. The Flag Current is always higher than Current Limit Threshold to ensure

maximum loading consuming.

When the ILIM pin is shorted to GND, current-limit threshold and short-circuit current limit will be clamped at typically 100mA. When the ILIM pin is

shorted to GND, the AP22652/53 and AP22652A/53A FAULT pin will assert during current-limiting and short-circuit conditions.

For latch-off version, once Fault signal is triggered, the device will stay off until EN pin is toggled or power is restarted.

Power Supply Considerations

A 0.01μF to 0.1μF, X7R or X5R ceramic bypass capacitor between IN and GND, close to the device, is recommended. This limits the input voltage

drop during line transients. Placing a high-value electrolytic capacitor on the input (10μF minimum) and output pin (120µF) is recommended when

the output load is heavy. This precaution also reduces power-supply transients that may cause ringing on the input. Additionally, bypassing the

device output with a 0.1μF to 4.7μF ceramic capacitor improves the immunity of the device to short-circuit transients. This capacitor also prevents

output from going negative during turn-off due to parasitic inductance.

Power Dissipation and Junction Temperature

The low on-resistance of the internal MOSFET allows the small surface-mount packages to pass large current. Using the maximum operating

ambient temperature (TA) and RDS(ON), the power dissipation can be calculated by:

PD = RDS(ON)× I2

Finally, calculate the junction temperature:

TJ = PD x ΘJA + TA

Where:

TA = Ambient temperature °C

θJA = Thermal resistance

PD = Total power dissipation

Generic Hot-Plug Applications

In many applications, it may be necessary to remove modules or PC boards while the main unit is still operating. These are considered hot-plug

applications. Such implementations require the control of current surges seen by the main power supply and the card being inserted. The most

effective way to control these surges is to limit and slowly ramp the current and voltage being applied to the card, similar to the way in which a

power supply normally turns on. Due to the controlled rise and fall times of the AP22652/52A and AP22653/53A these devices can be used to

provide a softer start-up to devices being hot-plugged into a powered system. The UVLO feature of the AP22652/52A and AP22653/53A also

ensures that the switch is off after the card has been removed, and that the switch is off during the next insertion.

Generic Hot-Plug Applications

By placing the AP22652/52A and AP22653/53A between the VCC input and the rest of the circuitry, the input power reaches these devices first

after insertion. The typical rise time of the switch is approximately 1ms, providing a slow voltage ramp at the output of the device. This

implementation controls system surge current and provides a hot-plugging mechanism for any device.