NXP Semiconductors
74HC123; 74HCT123
Dual retriggerable monostable multivibrator with reset
12. Application information
12.1 Timing component connections
The basic output pulse width is essentially determined by the values of the external timing
components R
EXT
and C
EXT
.
CEXT
(1)
REXT
V
CC
nCEXT
14 (6)
nREXT/CEXT
15 (7)
13 (5)
nQ
GND
8
123
nA
nB
1 (9)
2 (10)
4 (12)
nQ
3 (11)
nRD
001aaa854
(1) For minimum noise generation it is recommended to ground pins 6 (2CEXT) and 14 (1CEXT)
externally to pin 8 (GND).
Fig 13. Timing component connections
12.2 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
EXT
and C
EXT
. This output pulse can be eliminated using the
circuit shown in
CEXT
REXT
V
CC
GND
8
nCEXT
14 (6)
nREXT/CEXT
15 (7)
13 (5)
nQ
123
nA
nB
1 (9)
2 (10)
4 (12)
nQ
3 (11)
nRD
RESET
V
CC
001aaa613
Fig 14. Power-up output pulse elimination circuit
74HC_HCT123_5
© NXP B.V. 2009. All rights reserved.
Product data sheet
Rev. 05 — 13 July 2009
15 of 24
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