AP22908

Document number: DS42262 Rev. 5 - 2

13 of 19

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February 2023

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AP22908

Application Information

Input Capacitor

A 1μF capacitor is recommended to connect between VIN and GND pins to decouple input power supply glitch and noise. The input capacitor has

no specific type or ESR (Equivalent Series Resistance) requirement. However, for higher current application, ceramic capacitors are

recommended due to their capability to withstand input current surges from low impedance sources, such as batteries in portable applications.

This input capacitor must be located as close as possible to the device to assure input stability and less noise. For PCB layout, a wide copper

trace is required for both VIN and GND.

Output Capacitor

The 0.1μF to 1μF capacitor is recommended to connect between VOUT and GND pins to stabilize and accommodate load transient condition. The

output capacitor has no specific type or ESR requirement. The amount of the capacitance may be increased without limit. For PCB layout, the

output capacitor must be placed as close as possible to VOUT and GND pins, and keep the traces as short as possible.

Enable/Shutdown Operation

The AP22908 is turned on by setting the ON pin high, and is turned off by pulling it low. To ensure proper operation, the signal source used to

drive the ON pin must be able to swing above and below the specified turn-on/off voltage thresholds listed in the Electrical Characteristics section

under VIL and VIH.

Discharge Operation

The AP22908 offers discharge option that helps to discharge the output charge when disabled. The discharge resistance with a typical value of

80Ω is connected between the output and ground.

Power Dissipation

The maximum IC junction temperature should be restricted to +125°C under normal operating conditions. The device power dissipation and proper

sizing of the thermal plane is critical to avoid thermal shutdown and ensure reliable operation. Power dissipation of the device depends on input

voltage and load conditions and can be calculated by:

DSON

2

OUT

D

xR

I

P



(1)

However, the maximum power dissipation that can be handled by the device depends on the maximum junction to ambient thermal resistance,

maximum ambient temperature, and maximum device junction temperature, which can be approximated by the equation below:

JA

A

)

MAX

(

D

)

T

C

125

(

P









(2)

Layout Guildline

Good PCB layout is important for improving the thermal performance of the device. All trace lengths should be kept as short as possible. The input

(VIN) and output (VOUT) PCB traces should be as wide as possible to reduce stray impedance.

Use a ground plane to enhance the power dissipation capability of the device if applicable. Place input and output capacitors close to the device to

minimize the effects of parasitic inductance.