74HC4538 Datasheet, PDF (11/13 Pages) NXP Semiconductors – Dual retriggerable precision monostable multivibrator

Philips Semiconductors
Product specification
Dual retriggerable precision monostable
multivibrator
74HC/HCT4538
Fig.11 Power-down protection 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 sustain 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.11.
Fig.12 Typical pulse width accuracy versus external capacitance; V_CC = 4.5 V; T_amb = 25 °C.
Fig.13 Typical pulse width accuracy versus external resistance; V_CC = 4.5 V; T_amb = 25 °C.
September 1993
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