74HC123 Datasheet, PDF (16/24 Pages) NXP Semiconductors – Dual retriggerable monostable multivibrator with reset

NXP Semiconductors
74HC123; 74HCT123
Dual retriggerable monostable multivibrator with reset
12.3 Power-down considerations
A large capacitor C_EXT 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_EXT) preferably a germanium or Schottky type
diode able to withstand large current surges and connect as shown in Figure 15.
DEXT
CEXT
REXT
V_CC
GND nCEXT nREXT/CEXT
8
14 (6)
15 (7)
123
1 (9)
nA
nB
2 (10)
13 (5)
nQ
4 (12)
nQ
Fig 15. Power-down protection circuit
3 (11)
nRD
001aaa614
74HC_HCT123_5
Product data sheet
Rev. 05 — 13 July 2009
© NXP B.V. 2009. All rights reserved.
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