L78 datasheet(29/55 Pages) STMICROELECTRONICS

Part #	L78

Description	Positive voltage regulator ICs

PDF	55 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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29 / 55 page

Figure 27. Light controllers (VO(min) = VXX + VBE)

VO rises when the light goes up

VO falls when the light goes up

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Figure 28. Protection against input short-circuit with high capacitance loads

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Note:

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

Figure 23. Reducing power dissipation with dropping resistor) 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.

L78

Design consideration

DS0422 - Rev 36

page 29/55

L78 Datasheet(PDF) 29 Page - STMicroelectronics