GND

IN

EN

LP38513

Thermal

Limit

Current

Limit

ERROR

OUT

LP38513

SNVS361E – JULY 2007 – REVISED NOVEMBER 2015

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7 Detailed Description

7.1 Overview

The LP38513 is a fast response, ultra-low-dropout linear regulator that operates from a 2.25-V to 5.5-V input

supply. This linear regulator responds very quickly to step changes in line or load conditions, making it suitable

for low-voltage microprocessor applications. The device has low quiescent current operation that is independent

nominal regulated voltage.

The LP38513 is designed to perform with a10-µF (minimum value) input capacitor and a 10-µF (minimum value)

output capacitor.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Short-Circuit Protection

The LP38513 is short-circuit protected and, in the event of a peak overcurrent condition, the short-circuit control

loop rapidly drives the output PMOS pass element off. Once the power pass element shuts down, the control

loop rapidly cycles the output on and off until the average power dissipation causes the thermal shutdown circuit

to respond to servo the on/off cycling to a lower frequency. Refer to the Power Dissipation section for power

dissipation calculations.

7.3.2 Enable

LP38513 has an EN pin to enable/disable the device. If the application does not require the enable function, the

pin must be connected directly to the adjacent IN pin.

The status of the EN pin also affects the behavior of the ERROR flag. While the EN pin is high the regulator

control loop is active, and the ERROR flag reorts the status of the output voltage. When the EN pin is taken low

the regulator control loop is shut down, the output is turned off, and the internal logic immediately forces the

ERROR flag pin low.

7.3.3 ERROR Flag

When the LP38513 EN pin is high, the ERROR flag pin produces a logic low signal when the output drops by

input voltage, current limiting, or thermal limiting. This flag has a built-in hysteresis. The output voltage must to

rise to greater than typically 89% of the nominal output voltage for the ERROR flag to return to a logic high state.

Also, if the EN pin is pulled low, the ERROR flag pin is forced to low as well.

10

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