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LDK715

Electrical characteristics

18

4.1

External capacitor requirements

A 0.1 µF or a larger input bypass capacitor, connected between IN and GND and located

close to the device, is recommended. In this manner, the transient response and noise

rejection of the power supply, as a whole, improve. A higher value of the input capacitor may

be necessary if large, fast-rise-time load transients are present in the application and if the

device is several inches far from the power source.

The LDK715 requires an output capacitor connected between OUT and GND to stabilize the

internal control loop. Please refer to Figure 7. for the allowable output capacitance and ESR

combinations.

4.2

Power dissipation and junction temperature

For a reliable operation, junction temperature should not exceed 125 °C. This limits the

power dissipation the regulator can handle in any application. To guarantee that the junction

temperature is within acceptable limits, calculate the maximum allowable dissipation,

The maximum power dissipation limit is given by the following equation:

Equation 1

where:

The regulator dissipation is calculated by the following equation:

Equation 2

Power dissipation coming from quiescent current is negligible.

The ST715 features the internal current limit. During normal operation, it limits the output

current to approximately 350 mA. When the current limit engages, the output voltage scales

back linearly until the overcurrent condition ends. Do not exceed the power dissipation

ratings of the package.

P

Dmax

()

T

JMAX

T

A

–

() R

thJA

⁄

=

P

D

V

IN

V

out

–

() I

out

×

=