L78 datasheet(30/54 Pages) STMICROELECTRONICS

No. de pieza	L78

Descripción Electrónicos	Thermal overload protection

PDF	54 Pages

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Fabricante Electrónico	STMICROELECTRONICS [STMicroelectronics]

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Application information

L78

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DocID2143 Rev 34

Figure 25: Adjustable output voltage with temperature compensation

Q2 is connected as a diode in order to compensate the variation of the Q1 VBE with

the temperature. C allows a slow rise time of the VO.

Figure 26: Light controllers (VO(min) = VXX + VBE)

Figure 27: Protection against input short-circuit with high capacitance loads

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

need an external diode (see Figure 22: "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 Datasheet(PDF) 30 Page - STMicroelectronics