74HC423 Datasheet, PDF (10/23 Pages) NXP Semiconductors – Dual retriggerable monostable multivibrator with reset

NXP Semiconductors
74HC423; 74HCT423
Dual retriggerable monostable multivibrator with reset
Table 7. Dynamic characteristics …continued
GND = 0 V; test circuit see Figure 12.
Symbol Parameter Conditions
C_PD
power
per package; V_I = GND to V_CC − 1.5 V
dissipation
capacitance
25 °C
−40 °C to −40 °C to Unit
+85 °C +125 °C
Min Typ Max Min Max Min Max
[6] _-
56
-
-
-
-
- pF
[1] t_pd is the same as t_PHL and t_PLH.
[2] t_t is the same as t_THL and t_TLH.
[3] For other R_EXT and C_EXT combinations see Figure 8. If C_EXT > 10 pF, the next formula is valid:
t_W = K × R_EXT × C_EXT (typ.), where:
t_W = output pulse width in ns;
R_EXT = external resistor in kΩ;
C_EXT = external capacitor in pF;
K = 0.55 for V_CC = 2.0 V and 0.45 for V_CC = 5.0 V; see Figure 9.
Inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is 7 pF.
[4] 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 set-up time of a retrigger pulse is valid:
t_rtrig = 30 + 0.19 × R_EXT × C_EXT0.9 + 13 × R_EXT1.05 (typ.); where:
t_rtrig = retrigger time in ns;
C_EXT = external capacitor in pF;
R_EXT = external resistor in kΩ.
Inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is 7 pF.
[5] When the device is powered-up, initiate the device via a reset pulse, when C_EXT < 50 pF.
[6] C_PD is used to determine the dynamic power dissipation (P_D in µW):
P_D = C_PD × V_CC2 × f_i × N + ∑ (C_L × V_CC2 × f_o); where:
f_i = input frequency in MHz;
f_o = output frequency in MHz;
C_L = output load capacitance in pF;
V_CC = supply voltage in V;
N = number of inputs switching;
∑ (C_L × V_CC2 × f_o) = sum of outputs.
74HC_HCT423_3
Product data sheet
Rev. 03 — 24 July 2008
© NXP B.V. 2008. All rights reserved.
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