LP2951 datasheet(22/47 Pages) TI

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7 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, as well as validating and testing their design

implementation to confirm system functionality.

7.1 Application Information

The LP2951-Q1 is used as a low-dropout regulator with a wide range of input voltages.

7.1.1 Reverse Current

Excessive reverse current potentially damages this device. Reverse current flows through the intrinsic body

diode of the pass transistor instead of the normal conducting channel. At high magnitudes, this current flow

degrades the long-term reliability of the device.

Conditions where reverse current occurs are outlined in this section, all of which potentially exceed the absolute

maximum rating of VOUT ≤ VIN + 0.3V.

• If the device has a large COUT and the input supply collapses with little or no load current

• The output is biased when the input supply is not established

• The output is biased above the input supply

If reverse current flow is expected in the application, use external protection to protect the device. Reverse

current is not limited in the device, so external limiting is required if extended reverse voltage operation is

anticipated.

Figure 7-1 shows one approach for protecting the device.

OUT

GND

CIN

GND

COUT

GND

Internal Body Diode

Schottky Diode

Figure 7-1. Example Circuit for Reverse Current Protection Using a Schottky Diode

7.1.2 Input and Output Capacitor Requirements

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

from IN to GND. This capacitor counteracts reactive input sources and improves transient response, input ripple,

and PSRR. Use an input capacitor if the source impedance is more than 0.5Ω. Use a higher value capacitor if

large, fast rise-time load or line transients are anticipated or if the device is located several inches from the input

power source.

Dynamic device performance is improved by using an output capacitor. Use an output capacitor within the range

specified in the Recommended Operating Conditions table for stability.

LP2951-Q1

SLVSAW6H – JUNE 2011 – REVISED NOVEMBER 2024

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