NXP Semiconductors
74HC123; 74HCT123
Dual retriggerable monostable multivibrator with reset
Table 7.
Dynamic characteristics
…continued
Voltages are referenced to GND (ground = 0 V); C
L
= 50 pF unless otherwise specified; for test circuit see
Figure 12.
Symbol Parameter
t
W
pulse width
Conditions
Min
V
CC
= 4.5 V
nA LOW; see
nB HIGH; see
nRD LOW; see
nQ HIGH and nQ LOW;
V
CC
= 5.0 V;
see
and
C
EXT
= 100 nF;
R
EXT
= 10 kΩ
C
EXT
= 0 pF;
R
EXT
= 5 kΩ
t
rtrig
retrigger time
nA, nB; C
EXT
= 0 pF;
R
EXT
= 5 kΩ; V
CC
= 5.0 V;
see
25
°C
Typ
3
5
7
Max
-
-
-
−40 °C
to +85
°C −40 °C
to +125
°C
Unit
Min
25
25
25
Max
-
-
-
Min
30
30
30
Max
-
-
-
ns
ns
ns
20
20
20
-
-
-
450
75
110
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
µs
ns
ns
R
EXT
C
EXT
C
PD
external timing V
CC
= 5.0 V; see
resistor
external timing V
CC
= 5.0 V; see
capacitor
power
dissipation
capacitance
per monostable;
V
I
= GND to V
CC
2
-
-
-
-
56
1000
-
-
-
-
-
-
-
-
-
-
-
-
-
-
kΩ
pF
pF
[1]
[2]
t
pd
is the same as t
PHL
and t
PLH
; t
t
is the same as t
THL
and t
TLH
For other R
EXT
and C
EXT
combinations see
If C
EXT
> 10 nF, the next formula is valid.
t
W
= K
×
R
EXT
×
C
EXT
, where:
t
W
= typical output pulse width in ns;
R
EXT
= external resistor in kΩ;
C
EXT
= external capacitor in pF;
K = constant = 0.45 for V
CC
= 5.0 V and 0.55 for V
CC
= 2.0 V.
The inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is approximately 7 pF.
[3]
The time to retrigger the monostable multivibrator depends on the values of R
EXT
and C
EXT
. The output pulse width will only be
extended when the time between the active-going edges of the trigger input pulses meets the minimum retrigger time. If C
EXT
>10 pF,
the next formula (at V
CC
= 5.0 V) for the setup time of a retrigger pulse is valid:
t
rtrig
= 30 + 0.19
×
R
EXT
×
C
EXT0.9
+ 13
×
R
EXT1.05
, where:
t
rtrig
= retrigger time in ns;
C
EXT
= external capacitor in pF; R
EXT
= external resistor in kΩ.
The inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is 7 pF.
[4]
[5]
When the device is powered-up, initiate the device via a reset pulse, when C
EXT
< 50 pF.
C
PD
is used to determine the dynamic power dissipation (P
D
in
µW).
P
D
= C
PD
×
V
CC2
×
f
i
+
∑(C
L
×
V
CC2
×
f
o
) + 0.75
×
C
EXT
×
V
CC2
×
f
o
+ D
×
16
×
V
CC
where:
f
i
= input frequency in MHz;
f
o
= output frequency in MHz;
D = duty factor in %;
C
L
= output load capacitance in pF;
V
CC
= supply voltage in V;
C
EXT
= timing capacitance in pF;
∑(C
L
×
V
CC2
×
f
o
) sum of outputs.
74HC_HCT123_5
© NXP B.V. 2009. All rights reserved.
Product data sheet
Rev. 05 — 13 July 2009
10 of 24
PHILIPS [ NXP SEMICONDUCTORS ]
