HC123 datasheet(11/17 Pages) PHILIPS

11 / 17 page

1998 Jul 08

Philips Semiconductors

Product speciﬁcation

Dual retriggerable monostable

multivibrator with reset

74HC/HCT123

APPLICATION INFORMATION

Power-up considerations

When the monostable is powered-up it may produce an

output pulse, with a pulse width defined by the values of RX

and CX, this output pulse can be eliminated using the

circuit shown in Fig.11.

Power-down considerations

A large capacitor (CX) may cause problems when

powering-down the monostable due to the energy stored

in this capacitor. When a system containing this device is

powered-down or a rapid decrease of VCC to zero occurs,

the monostable may substain damage, due to the

capacitor discharging through the input protection diodes.

To avoid this possibility, use a damping diode (DX)

preferably a germanium or Schottky type diode able to

withstand large current surges and connect as shown in

Fig.12

Fig.11 Power-up output pulse elimination circuit.

Fig.12 Power-down protection circuit.

HC123 Datasheet(PDF) 11 Page - NXP Semiconductors