Datasheet

1998 Jul 08 11
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 R
X
and C
X
, this output pulse can be eliminated using the
circuit shown in Fig.11.
Power-down considerations
A large capacitor (C
X
) 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 V
CC
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 (D
X
)
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.