GND

IN

EN

LP38511

Thermal

Limit

Current

Limit

ERROR

OUT

LP38511

www.ti.com

SNOSAU6E – NOVEMBER 2007 – REVISED APRIL 2013

BLOCK DIAGRAM

APPLICATION INFORMATION

EXTERNAL CAPACITORS

Like any low-dropout regulator, external capacitors are required to assure stability. These capacitors must be

correctly selected for proper performance.

Input Capacitor

A ceramic input capacitor of at least 10 µF is required. For general usage across all load currents and operating

conditions, a 10 µF ceramic input capacitor will provide satisfactory performance.

Output Capacitor

A ceramic capacitor with a minimum value of 10 µF is required at the output pin for loop stability. It must be

located less than 1 cm from the device and connected directly to the output and ground pin using traces which

have no other currents flowing through them. As long as the minimum of 10 µF ceramic is met, there is no

limitation on any additional capacitance.

X7R and X5R dielectric ceramic capacitors are strongly recommended, as they typically maintain a capacitance

range within ±20% of nominal over full operating ratings of temperature and voltage. Of course, they are typically

larger and more costly than Z5U/Y5U types for a given voltage and capacitance.

Z5U and Y5V dielectric ceramics are not recommended as the capacitance will drops severely with applied

voltage. A typical Z5U or Y5V capacitor can lose 60% of its rated capacitance with half of the rated voltage

applied to it. The Z5U and Y5V also exhibit a severe temperature effect, losing more than 50% of nominal

capacitance at high and low limits of the temperature range.

REVERSE VOLTAGE

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

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 output pin back to the input during a reverse voltage

condition.

Copyright © 2007–2013, Texas Instruments Incorporated

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