Nexperia 74HC123; 74HCT123
Dual retriggerable monostable multivibrator with reset
25 °C -40 °C to +85 °C -40 °C to +125 °CSymbol Parameter Conditions
Min Typ Max Min Max Min Max
Unit
CPD power
dissipation
capacitance
per monostable;
VI = GND to VCC - 1.5 V
[5] - 56 - - - - - pF
[1] tpd is the same as tPHL and tPLH; tt is the same as tTHL and tTLH
[2] For other REXT and CEXT combinations see Fig. 7. If CEXT > 10 nF, the next formula is valid.
tW = K × REXT × CEXT, where:
tW = typical output pulse width in ns;
REXT = external resistor in kΩ;
CEXT = external capacitor in pF;
K = constant = 0.45 for VCC = 5.0 V and 0.55 for VCC = 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 REXT and CEXT. 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 CEXT >10 pF,
the next formula (at VCC = 5.0 V) for the setup time of a retrigger pulse is valid:
trtrig = 30 + 0.19 × REXT × CEXT 0.9 + 13 × REXT 1.05, where:
trtrig = retrigger time in ns;
CEXT = external capacitor in pF; REXT = external resistor in kΩ.
The inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is 7 pF.
[4] When the device is powered-up, initiate the device via a reset pulse, when CEXT < 50 pF.
[5] CPD is used to determine the dynamic power dissipation (PD in μW).
PD = CPD x VCC 2 x fi + Σ(CL x VCC 2 x fo) + 0.75 x CEXT x VCC 2 x fo + D x 16 × VCC where:
fi = input frequency in MHz;
fo = output frequency in MHz;
D = duty factor in %;
CL = output load capacitance in pF;
VCC = supply voltage in V;
CEXT = timing capacitance in pF;
Σ(CL x VCC 2 x fo) sum of outputs.
001aaa611
103
102
105
104
106
tW
(ns)
10
CEXT (pF)
1 104
103
10 102
(2)
(3)
(4)
(1)
VCC = 5.0 V; Tamb = 25 °C.
(1) REXT = 100 kΩ
(2) REXT = 50 kΩ
(3) REXT = 10 kΩ
(4) REXT = 2 kΩ
Fig. 7. Typical output pulse width as a function of the
external capacitor value
VCC (V)
0 862 4
001aaa612
0.4
0.2
0.6
0.8
'K' factor
0
CEXT = 10 nF; REXT = 10 kΩ to 100 kΩ.
Tamb = 25 °C.
Fig. 8. 74HC123 typical ‘K’ factor as function of VCC
74HC_HCT123 All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2020. All rights reserved
Product data sheet Rev. 11.1 — 3 September 2020 10 / 21