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APPLICATION INFORMATION

DEVICE OPERATION

NC

OUT

1

3

IN

EN

GND

2

4

5

0.1

µF

TPS721xx

0.1

µF

DUAL SUPPLY APPLICATION

TPS72101

,, TPS72115

TPS72116, TPS72118

SLVS352C – DECEMBER 2001 – REVISED MARCH 2006

The TPS721xx family of low-dropout (LDO) regulators functions with a very low input voltage (>1.8 V). The

dropout voltage is typically 150 mV at full load. Typical quiescent current (ground pin current) is only 85 µA and

drops to 1 µA in the shutdown mode.

The TPS721xx family can be operated at low input voltages due to low voltage circuit design techniques and a

PMOS pass element that exhibits low dropout.

A logic low on the enable input, EN, shuts off the output and reduces the supply current to less than 1 µA. EN

Current limiting and thermal protection prevent damage by excessive output current and/or power dissipation.

The device switches into a constant-current mode at approximately 350 mA; further load reduces the output

voltage instead of increasing the output current. The thermal protection shuts the regulator off if the junction

temperature rises above 170°C. Recovery is automatic when the junction temperature drops approximately 20°C

below the high temperature trip point. The PMOS pass element includes a back diode that safely conducts

reverse current when the input voltage level drops below the output voltage level.

A typical application circuit is shown in Figure 18.

Figure 18. Typical Application Circuit

In portable, battery-powered electronics, separate power rails for the DSP or microcontroller core voltage,

voltage to a boost converter and the TPS72115 LDO linear regulator. The batteries combine input voltage ranges

from 3.0 V down to 1.8 V near the end of their useful lives. Therefore, a boost converter is necessary to provide

any switching type boost converter due to the inherent slow start up of those types of converters. Assuming a

the entire life of the two off-the-shelf AAA batteries. Thus, this solution is very efficient and the design time and

overall cost of the solution is minimized.

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