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74HCT423D ,Dual retriggerable monostable multivibrator with resetGENERAL DESCRIPTIONFor pulse widths, when C < 10 000 pF, see Fig.9.EXTWhen C > 10 000 pF, the typic ..
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74HC423D-74HC423N-74HCT423D
Dual retriggerable monostable multivibrator with reset
Philips Semiconductors Product specification
Dual retriggerable monostable
multivibrator with reset 74HC/HCT423
FEATURES DC triggered from active HIGH or active LOW inputs Retriggerable for very long pulses up to 100% duty
factor Direct reset terminates output pulse Schmitt-trigger action on all inputs except for the reset
input Output capability: standard (except for nREXT/CEXT) ICC category: MSI
GENERAL DESCRIPTIONThe 74HC/HCT423 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT423 are dual retriggerable monostable
multivibrators with output pulse width control by two
methods. The basic pulse time is programmed by
selection of an external resistor (REXT) and capacitor
(CEXT). The external resistor and capacitor are normally
connected as shown in Fig.6.
Once triggered, the basic output pulse width may be
extended by retriggering the gated active LOW-going edge
input (nA) or the active HIGH-going edge input (nB). By
repeating this process, the output pulse period
(nQ= HIGH, nQ = LOW) can be made as long as desired.
When nRD is LOW, it forces the nQ output LOW, the output HIGH and also inhibits the triggering.
Figures 7 and 8 illustrate pulse control by reset. The basic
output pulse width is essentially determined by the values
of the external timing components REXT and CEXT.
For pulse widths, when CEXT< 10 000 pF, see Fig.9.
When CEXT> 10 000 pF, the typical output pulse width is
defined as:= 0.45× REXT× CEXT (typ.),
where, tW= pulse width in ns;
REXT= external resistor in kΩ;
CEXT= external capacitor in pF.
Schmitt-trigger action in the nA and nB inputs, makes the
circuit highly tolerant to slower input rise and fall times.
The “423” is identical to the “123” but cannot be triggered
via the reset input.
QUICK REFERENCE DATAGND = 0 V; Tamb = 25 °C; tr = tf = 6 ns
Notes CPD is used to determine the dynamic power dissipation (PDin μW): = CPD× VCC2×fi +∑ (CL× VCC2×fo)+ 0.75× CEXT× VCC2×fo+D×16× VCC where: = input frequency in MHz = output frequency in MHz = duty factor in % (CL× VCC2×fo) = sum of outputs= output load capacitance in pF
VCC= supply voltage in V
CEXT= timing capacitance in pF For HC the condition is VI = GND to VCC
For HCT the condition is VI = GND to VCC− 1.5 V
Philips Semiconductors Product specification
Dual retriggerable monostable
multivibrator with reset 74HC/HCT423
ORDERING INFORMATION
PIN DESCRIPTION
Philips Semiconductors Product specification
Dual retriggerable monostable
multivibrator with reset 74HC/HCT423
FUNCTION TABLE
Notes H = HIGH voltage level = LOW voltage level= don’t care= LOW-to-HIGH transition= HIGH-to-LOW transition one HIGH level output pulse one LOW level output pulse If the monostable was triggered before this condition was established, the pulse will continue as programmed.
Philips Semiconductors Product specification
Dual retriggerable monostable
multivibrator with reset 74HC/HCT423
Philips Semiconductors Product specification
Dual retriggerable monostable
multivibrator with reset 74HC/HCT423
DC CHARACTERISTICS FOR 74HCFor the DC characteristics see “74HC/HCT/HCU/HCMOS Logic Family Specifications”.
Output capability: standard (except for nREXT /CEXT)
ICC category: MSI
AC CHARACTERISTICS FOR 74HCGND = 0 V; tr = tf = 6 ns; CL = 50 pF
Philips Semiconductors Product specification
Dual retriggerable monostable
multivibrator with reset 74HC/HCT423
DC CHARACTERISTICS FOR 74HCTFor the DC characteristics see “74HC/HCT/HCU/HCMOS Logic Family Specifications”.
Output capability: standard (except for nREXT/CEXT)
ICC category: MSI
Note to HCT typesThe value of additional quiescent supply current (ΔICC) for a unit load of 1 is given in the family specifications.
To determine ΔICC per input, multiply this value by the unit load coefficient shown in the table below.
AC CHARACTERISTICS FOR 74HCTGND = 0 V; tr = tf = 6 ns; CL = 50 pF
