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APPLICATION INFORMATION

TPS715A33

IN

OUT

V

IN

V

OUT

C1

0.1

µF

0.47

µF

GND

External Capacitor Requirements

Power Dissipation and Junction Temperature

P

T

R

q

JA

(1)

P

I

OUT

(2)

Regulator Protection

TPS715A01

TPS715A33

SBVS047A – MAY 2004 – REVISED DECEMBER 2004

The TPS715Axx family of LDO regulators has been optimized for ultra low power applications such as the

MSP430 microcontroller. Its ultralow supply current maximizes efficiency at light loads, and its high input voltage

range makes it suitable for supplies such as unconditioned solar panels.

Figure 14. Typical Application Circuit (Fixed Voltage Version)

Although not required, a 0.047-µF or larger input bypass capacitor, connected between IN and GND and located

close to the device, is recommended to improve transient response and noise rejection of the power supply as a

whole. A higher-value input capacitor may be necessary if large, fast-rise-time load transients are anticipated and

if the device is located several inches from the power source.

The TPS715Axx requires an output capacitor connected between OUT and GND to stabilize the internal control

loop. Any capacitor (including ceramic and tantalum) that is

≥ 0.47 µF properly stabilizes this loop.

To ensure reliable operation, worst-case junction temperature should not exceed 150

°C. This restriction limits the

power dissipation the regulator can handle in any given application. To ensure the junction temperature is within

The maximum-power-dissipation limit is determined using Equation 1:

where:

•

•

•

The regulator dissipation is calculated using Equation 2:

Power dissipation resulting from quiescent current is negligible.

The TPS715Axx PMOS-pass transistor has a built-in back diode that conducts reverse current when the input

voltage drops below the output voltage (for example, 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 TPS715Axx features internal current limiting. During normal operation, the TPS715Axx limits output current

to approximately 500 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.

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