ON

OFF

C

= 1

F

IN

µ

GND

V

IN

V

BATT

C

L

GND

R

L

C

L

V

OUT

SMPS

(see Note A)

GND

TPS22921/22/22B

LOAD

TPS22921, TPS22922, TPS22922B

www.ti.com

SLVS749C – NOVEMBER 2008 – REVISED JANUARY 2015

11 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

11.1 Application Information

11.1.1 Input Capacitor (Optional)

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

discharged load capacitor, 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, TI recommends using an input capacitor about

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

11.1.2 Output Capacitor (Optional)

Because of 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.

11.2 Typical Application

A.

Switched-mode power supply

Figure 53. Typical Application

11.2.1 Design Requirements

Table 2. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

VIN

1.8 V

CL

4.7 µF

Load current

2 A

Ambient Temperature

25 °C

Maximum inrush current

200 mA

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