Thermal

Limit

Soft-Start

Discharge

OUT

V

OUT

FB

PG

IN

BIAS

SS

EN

Hysteresis

andDe-Glitch

Current

Limit

UVLO

0.73 A

m

0.8V

Reference

0.9 ´ V

REF

GND

C

SS

R

1

R

2

V

=0.8x(

)

OUT

1+

R

1

R

2

TPS74201

www.ti.com

SBVS064M – DECEMBER 2005 – REVISED OCTOBER 2015

7 Detailed Description

7.1 Overview

The TPS742 belongs to a family of generation ultra-low dropout regulators that feature soft-start and tracking

capabilities. These regulators use a low current bias input to power all internal control circuitry, allowing the

NMOS pass transistor to regulate very low input and output voltages.

The use of an NMOS-pass FET offers several critical advantages for many applications. Unlike a PMOS topology

device, the output capacitor has little effect on loop stability. This architecture allows the TPS742 devices to be

stable with any or even no output capacitor. Transient response is also superior to PMOS topologies, particularly

The TPS742 devices feature a programmable voltage-controlled soft-start circuit that provides a smooth,

monotonic start-up and limits start-up inrush currents that may be caused by large capacitive loads. A power-

good (PG) output is available to allow supply monitoring and sequencing of other supplies. An enable (EN) pin

voltages often present in processor intensive systems.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Enable and Shutdown

circuitry has hysteresis and deglitching for use with relatively slow-ramping analog signals. This configuration

allows the TPS742 devices to be enabled by connecting the output of another supply to the EN pin. The enable

circuitry typically has 50 mV of hysteresis and a deglitch circuit to help avoid ON and OFF cycling because of

The enable threshold is typically 0.8 V and varies with temperature and process variations. Temperature

variation is approximately –1 mV/°C; therefore, process variation accounts for most of the variation in the enable

threshold. If precise turnon timing is required, a fast rise-time signal should be used to enable the TPS742

devices.

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