TPS78227

GND

EN

IN

OUT

V

IN

V

OUT

1 F

m

1 F

m

4.2Vto5.5V

2.7V

On

Off

TPS78225-Q1, TPS78227-Q1

TPS78228-Q1, TPS78230-Q1

www.ti.com

SBVS138 – DECEMBER 2009

APPLICATION INFORMATION

APPLICATION EXAMPLES

The TPS782xx family of LDOs is factory-programmable to have a fixed output. Note that during startup or

Figure 15. Typical Application Circuit

INPUT AND OUTPUT CAPACITOR REQUIREMENTS

Although an input capacitor is not required for stability, it is good analog design practice to connect a 0.1-

μF to

1.0-

μF low equivalent series resistance (ESR) capacitor across the input supply near the regulator. This

capacitor counteracts reactive input sources and improves transient response, noise rejection, and ripple

rejection. A higher-value capacitor may be necessary if large, fast rise-time load transients are anticipated, or if

the device is not located near the power source. If source impedance is not sufficiently low, a 0.1-

μF input

capacitor may be necessary to ensure stability.

The TPS782xx series are designed to be stable with standard ceramic capacitors with values of 1.0

μF or larger

at the output. X5R- and X7R-type capacitors are best because they have minimal variation in value and ESR

over temperature. Maximum ESR should be less than 1.0

Ω. With tolerance and dc bias effects, the minimum

capacitance to ensure stability is 1

μF.

BOARD LAYOUT RECOMMENDATIONS TO IMPROVE PSRR AND NOISE PERFORMANCE

To improve ac performance (such as PSRR, output noise, and transient response), it is recommended that the

connected only at the GND pin of the device. In addition, the ground connection for the output capacitor should

connect directly to the GND pin of the device. High ESR capacitors may degrade PSRR.

INTERNAL CURRENT LIMIT

The TPS782xx is internally current-limited to protect the regulator during fault conditions. During current limit, the

output sources a fixed amount of current that is largely independent of output voltage. For reliable operation, the

device should not be operated in a current limit state for extended periods of time.

The PMOS pass element in the TPS782xx series has a built-in body diode that conducts current when the

voltage at OUT exceeds the voltage at IN. This current is not limited, so if extended reverse voltage operation is

anticipated, external limiting to 5% of rated output current may be appropriate.

Copyright © 2009, Texas Instruments Incorporated

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Product Folder Link(s): TPS78225-Q1 TPS78227-Q1 TPS78228-Q1 TPS78230-Q1