TPS22921 datasheet(21/27 Pages) TI

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APPLICATION INFORMATION

ON/OFF Control

Input Capacitor

Output Capacitor

Board Layout

TPS22921, TPS22922, TPS22922B

www.ti.com........................................................................................................................................ SLVS749A – NOVEMBER 2008 – REVISED DECEMBER 2008

The ON pin controls the state of the switch. Activating ON continuously holds the switch in the on state so long

as there is no fault. ON is active HI and has a low threshold making it capable of interfacing with low voltage

signals. The ON pin is compatible with standard GPIO logic threshold. It can be used with any microcontroller

with 1.2-V, 1.8-V, 2.5-V or 3.3-V GPIOs.

To limit the voltage drop on the input supply caused by transient in-rush currents when the switch turns on into a

discharged load capacitor or short-circuit, a capacitor must be placed between VIN and GND . A 1-µF ceramic

capacitor, CIN, placed close to the pins is usually sufficient. Higher values of CIN can be used to further reduce

the voltage drop during higher current application. When switching a heavy load, it is recommended to have an

input capacitor about 10 or more times higher than the output capacitor in order to avoid any supply drop.

Due to the integral body diode in the PMOS switch, a CIN greater than CL is highly recommended. A CL greater

than CIN can cause VOUT to exceed VIN when the system supply is removed. This could result in current flow

through the body diode from VOUT to VIN.

For best performance, all traces should be as short as possible. To be most effective, the input and output

capacitors should be placed close to the device to minimize the effects that parasitic trace inductances may have

on normal and short-circuit operation. Using wide traces for VIN, VOUT, and GND will help minimize the parasitic

electrical effects along with minimizing the case to ambient thermal impedance.

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Product Folder Link(s): TPS22921 TPS22922 TPS22922B

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