L7815CV-DG Datasheet, PDF (36/57 Pages) STMicroelectronics – Positive voltage regulator ICs

Application information
L78xx, L78xxC, L78xxAB, L78xxAC
Figure 28. Protection against input short-circuit with high capacitance loads
Note:
Application with high capacitance loads and an output voltage greater than 6 volts need an
external diode (see Figure 23 on page 34) 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.
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Doc ID 2143 Rev 30