SN54AHCT123A Datasheet, PDF (8/21 Pages) Texas Instruments – DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATORS

SN54AHCT123A, SN74AHCT123A
DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATORS
SCLS420G – JUNE 1998 – REVISED APRIL 2003
APPLICATION INFORMATION
retriggering data
The minimum input retriggering time (t_MIR) is the minimum time required after the initial signal before retriggering
the input. After t_MIR, the device retriggers the output. Experimentally, it also can be shown that to retrigger the
output pulse, the two adjacent input signals should be t_MIR apart, where t_MIR = 0.30 × t_w. The retrigger pulse
duration is calculated as shown in Figure 3.
tMIR
Input
Output
tPLH
tRT = tw + tPLH = (K × RT × CT) + tPLH
tRT
Where:
tw
tMIR = Minimum Input Retriggering Time
tPLH = Propagation Delay
tRT = Retrigger Time
tw = Output Pulse Duration Before Retriggering
Figure 3. Retrigger Pulse Duration
The minimum value from the end of the input pulse to the beginning of the retriggered output should be
approximately 15 ns to ensure a retriggered output (see Figure 4).
Input
Output
tMRT
tMRT = Minimum Time Between the End of the Second Input Pulse and the Beginning of the Retriggered Output
tMRT = 15 ns
Figure 4. Input/Output Requirements
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