74HC123 Datasheet, PDF (11/17 Pages) NXP Semiconductors – Dual retriggerable monostable multivibrator with reset

Philips Semiconductors
Dual retriggerable monostable
multivibrator with reset
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.
Product specification
74HC/HCT123
Fig.11 Power-up output pulse elimination circuit.
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.12 Power-down protection circuit.
1998 Jul 08
11