Output voltage selection for adjustable version

ST715XX, ST715XX25, ST715XX33

8/19

Doc ID 14414 Rev 7

5

Output voltage selection for adjustable version

The ST715xx features an adjustable output voltage using two external resistors connected

as a voltage divider to the FB pin as shown in the typical application circuit Figure 4. The

output voltage is set using the following equation:

Equation 1

accuracy, and high-frequency power-supply rejection. To simplify resistor selection use the

following equation:

Equation 2

5.1

External capacitor requirements

A 0.1 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 will be present in the application and if the device is located several

inches away from the power source.

The ST715xx requires an output capacitor connected between OUT and GND to stabilize

the internal control loop. Any capacitor (including ceramic and tantalum) with a value higher

than 0.47 µF will properly stabilize this loop.

5.2

Power dissipation and junction temperature

To ensure reliable operation, worst-case junction temperature should not exceed 125 °C.

This restriction limits the power dissipation the regulator can handle in any given application.

To ensure that the junction temperature is within acceptable limits, calculate the maximum

The maximum power dissipation limit is determined using the following equation:

Equation 3

where: