74HC123; 74HCT123
NXP Semiconductors
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 REXT and CEXT
.
C
EXT
R
EXT
(1)
V
CC
GND
8
nCEXT nREXT/CEXT
14 (6) 15 (7)
13 (5)
123
nQ
nQ
1 (9)
nA
nB
2 (10)
4 (12)
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 REXT and CEXT. This output pulse can be eliminated using the
circuit shown in Figure 14.
C
EXT
R
EXT
V
CC
GND
8
nCEXT
14 (6)
nREXT/CEXT
15 (7)
13 (5)
123
nQ
1 (9)
nA
nB
2 (10)
4 (12)
nQ
3 (11)
nRD
V
RESET
CC
001aaa613
Fig 14. Power-up output pulse elimination circuit
74HC_HCT123
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© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 8 — 16 December 2011
15 of 25
NXP [ NXP ]
