LP38693 datasheet(14/34 Pages) TI

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LP38691

OUT

SNS

GND

1 µF

VOUT

VIN

LP38693

OUT

SNS

GND

1 µF

VOUT

VIN

VEN

LP38691, LP38693, LP38691-Q1, LP38693-Q1

SNVS321N – JANUARY 2005 – REVISED MARCH 2015

www.ti.com

9 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.

9.1 Application Information

9.1.1 Reverse Voltage

A reverse voltage condition will exist when the voltage at the output pin is higher than the voltage at the input pin.

Typically this will happen when VIN is abruptly taken low and COUT continues to hold a sufficient charge such that

the input to output voltage becomes reversed. A less common condition is when an alternate voltage source is

connected to the output.

There are two possible paths for current to flow from the OUT pin back to IN during a reverse voltage condition.

1. While VIN is high enough to keep the control circuity alive, and the EN pin (LP38693 only) is above the

VEN(ON) threshold, the control circuitry will attempt to regulate the output voltage. If the input voltage is less

than the programmed output voltage, the control circuit will drive the gate of the pass element to the full ON

condition. In this condition, reverse current will flow from the OUT to the IN pin, limited only by the RDS(ON) of

the pass element and the output to input voltage differential. Discharging an output capacitor up to 1000

μF

in this manner will not damage the device as the current will rapidly decay. However, continuous reverse

current should be avoided. When the EN pin is low, this condition will be prevented.

2. The internal PFET pass element has an inherent parasitic diode. During normal operation, the input voltage

is higher than the output voltage and the parasitic diode is reverse biased. However, when VIN is below the

value where the control circuity is alive, or the EN pin is low (LP38693 only), and the output voltage is more

than 500 mV (typical) above the input voltage the parasitic diode becomes forward biased and current flows

from the output pin to the input pin through the diode. The current in the parasitic diode should be limited to

less than 1 A continuous and 5 A peak.

If used in a dual-supply system where the regulator output load is returned to a negative supply, the output

pin must be diode clamped to ground to limit the negative voltage transition. A Schottky diode is

recommended for this protective clamp.

9.2 Typical Application

* Minimum value required for stability.

**WSON package devices only.

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Product Folder Links: LP38691 LP38693 LP38691-Q1 LP38693-Q1

LP38693 Datasheet(PDF) 14 Page - Texas Instruments

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