L78Sxx, L78SxxC

Typical performance

Doc ID 2148 Rev 4

31/39

1.

Application with high capacitance loads and an output voltage greater than 6 volts need an external diode

(see Figure 30 on page 28) to protect the device against input short circuit. In this case the input voltage

falls rapidly while the output voltage decrease slowly. The capacitance discharges by means of the Base-

Emitter junction of the series pass transistor in the regulator. If the energy is sufficiently high, the transistor

may be destroyed. The external diode by-passes the current from the IC to ground.

Figure 37.

Protection against input short-circuit with high capacitance loads