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74HC123 5-10ms Pulse on Edge
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Topic: 74HC123 5-10ms Pulse on Edge (Read 1994 times)
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ripper121
Contributor
Posts: 21
74HC123 5-10ms Pulse on Edge
«
on:
November 28, 2016, 06:55:08 pm »
Hello:),
i have a Reed Contact which can be open or closed,on each change (Open to Close or Close to Open) Ineed a 5-10ms Pulse (HIGH-LOW-HIGH).
With 2uF and 10kOhm on CEXT and REXT i get about 6.75ms Pulse. (i used Page 10 Table 7 to calculate that).
On page 5 table 3 are the states.
http://www.nxp.com/documents/data_sheet/74HC_HCT123.pdf
Is my schematic and calculation correct?
Is it with this schematic possible?
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radar_macgyver
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Posts: 698
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Re: 74HC123 5-10ms Pulse on Edge
«
Reply #1 on:
November 29, 2016, 07:21:20 am »
Looks like you're in the ballpark.
http://www.ti.com/lit/an/scla014/scla014.pdf
Consider using a smaller C and larger R. The discharge current will be smaller, and hence the likelihood of that current causing ground bounce.
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ripper121
Contributor
Posts: 21
Re: 74HC123 5-10ms Pulse on Edge
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Reply #2 on:
November 29, 2016, 07:24:06 am »
Thank you for this info
.
Can you say something about my schematic, will it work?
Because there are some undefined states (not in the table)
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