74HC423 Datasheet, PDF (15/23 Pages) NXP Semiconductors – Dual retriggerable monostable multivibrator with reset

NXP Semiconductors
74HC423; 74HCT423
Dual retriggerable monostable multivibrator with reset
CEXT
REXT
V_CC
GND
nCEXT nREXT/CEXT
8
14 (6)
15 (7)
423
1 (9)
nA
nB
2 (10)
13 (5)
nQ
4 (12)
nQ
3 (11)
nRD
RESET
V_CC
Fig 14. Power-up output pulse elimination circuit
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12.3 Power-down considerations
A large capacitor C_EXT may cause problems when powering-down the monostable due to
the capacitor’s stored energy. 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
GND
8
423
nA
1 (9)
nB
2 (10)
Fig 15. Power-down protection circuit
CEXT
REXT
V_CC
nCEXT
14 (6)
nREXT/CEXT
15 (7)
13 (5)
nQ
4 (12)
nQ
3 (11)
nRD
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74HC_HCT423_3
Product data sheet
Rev. 03 — 24 July 2008
© NXP B.V. 2008. All rights reserved.
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