R1

R2

Fast

turnon and

turnoff

VREF

Overcurrent

Thermal Prot.

IN

EN

BYPASS

OUT

+

-

GND

LP3995

www.ti.com

SNVS179F – FEBRUARY 2003 – REVISED SEPTEMBER 2015

8 Detailed Description

8.1 Overview

The LP3995 device is a CMOS voltage regulator with a low input operating voltage tolerance. Key protection

circuits, including thermal-overload and short-circuit protection, are integrated in the device. Using the EN pin,

the device may be controlled to provide a shutdown state, in which negligible supply current is drawn. The

LP3995 is designed to be stable with space-saving ceramic capacitors.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Enable (EN)

The EN pin is used to control the ON or OFF status of the LP3995. The EN pin voltage must be higher than the

VIH threshold to ensure that the device is fully enabled under all operating conditions.

8.3.2 Fast Turnoff

When the EN pin voltage is lower than the VIL threshold, the output is disabled, and the pull-down circuitry is

activated to discharge the output capacitance.

8.3.3 Low Output Noise

The BYPASS pin is an external connection into the LP3995 band-gap circuitry allows the addition of an external

capacitor to reduce output noise . A fast-charge circuit is controlled by the enable circuitry to reduce start-up

delays. The capacitor on the BYPASS pin also prevents overshoot on the output during startup.

8.3.4 Output Capacitor

The LP3995 requires at least a 1-µF low ESR ceramic capacitor at the OUT pin.

8.3.5 Thermal Overload Protection (TSD)

Thermal shutdown disables the output when the junction temperature rises to approximately 160°C which allows

the device to cool. When the junction temperature cools to approximately 140°C, the output circuitry

automatically enables. Based on power dissipation, thermal resistance, and ambient temperature, the thermal

protection circuit may cycle on and off. This thermal cycling limits the dissipation of the regulator and protects it

from damage as a result of overheating. The thermal shutdown circuitry of the LP3995 has been designed to

protect against temporary thermal overload conditions. The thermal shutdown circuitry is not intended to replace

proper heat-sinking. Continuously running the LP3995 device into thermal shutdown may degrade device

reliability.

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Product Folder Links: LP3995