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TPS79718

PG

GND

0.47

µF

1.8 V

RESET

MSP430

or Equivalent

0.1

µF

+

−

TPS79718-EP, TPS79730-EP, TPS79733-EP

SGLS348A – AUGUST 2006 – REVISED OCTOBER 2007

Regulator Protection

The TPS797xx PMOS-pass transistor has a built-in back diode that conducts reverse current when the input

voltage drops below the output voltage (e.g., during power down). Current is conducted from the output to the

input and is not internally limited. If extended reverse voltage operation is anticipated, external limiting might be

appropriate.

The TPS797xx features internal current limiting. During normal operation, the TPS797xx limits output current to

approximately 190 mA. When current limiting engages, the output voltage scales back linearly until the

overcurrent condition ends. Take care not to exceed the power dissipation ratings of the package.

Microcontroller Application

One application for which this device is particularly suited is providing a regulated input voltage and power good

(PG) supervisory signal to low-power devices such as mixed-signal microcontrollers. The quiescent or ground

current of the TPS797xx family is typically 1.2

µA even at full load; therefore, the reduction in battery life by

including the TPS797xx in the system is negligible. The primary benefits of using the TPS797xx to power low

power digital devices include:

• Regulated output voltage that protects the device from battery droop and noise on the line (e.g., switch

bounce)

• Smooth, monotonic power up

• PG signal for controlled device RESET

• Potential to use an existing 5-V power rail to power a 3.3 V or lower device

• Potential to provide separate digital and analog power and ground supplies for a system with only one power

source

Figure 15 shows an application in which the TPS79718 is used to power Texas Instruments MSP430 mixed

signal microcontroller.

Figure 15. MSP430 Microcontroller Powered by the TPS79718 Regulator

Minimal board space is needed to accommodate the DCK (SC70/SOT-323) packaged TPS79718, the 0.1

µF

output capacitor, the 0.47

µF input capacitor, and the pullup resistor on the PG pin.

Copyright © 2006–2007, Texas Instruments Incorporated

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Product Folder Link(s): TPS79718-EP TPS79730-EP TPS79733-EP