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:
PD IOUT2xRDSON
(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:
(125C TA )
(2)
PD(MAX)
JA
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.
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March 2023
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AP22908
Document number: DS42262 Rev. 6 - 2