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I am using ADC0808CCN for a project on converting analog signal to digital signal. It has a built in multiplexer which we have to use to provide an analog signal to one of the pins. However what happens is:

  1. Sometimes it latches to a particular value say 1000000 and remains at there no matter how many times start of conversion is pressed which should set the inner counter to 0.

  2. Sometimes it gives slightly wrong output off by 100 or 1000 and when I press start of conversion, it gives correct output, so its not reliable every time.

  3. And most seriously, suppose the control for multiplexer according to datasheet are such that input pin 1 should be active, instead, it works only when the input is given to pin 5 for one particular IC and pin 3 for other.

Since the frequency of 555 clock is 33Hz I thought switch bouncing would be not a concern, hence avoided it.

I have been trying to fit it in logic since 3 days however each day some new error happens. I have replaced it twice from my college lab and now the technician doesn't want to replace it anymore . What is amiss here ?

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This is the circuit design taught to us for the similar ADC0804:

Since it doesn't use capacitors I ignored decoupling capacitors.

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JRE
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Kutsit
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    You ignored supply decoupling, and probably all the signal integrity rules for interfacing and now you wonder why your timing fails? – Tony Stewart EE75 Apr 02 '19 at 02:38
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    @SunnyskyguyEE75 You could have posted this in a less condescending manner, and it would be a good addition. Now it just looks cocky. – Willy Wonka Apr 02 '19 at 06:04
  • This is a duplicate of a question you asked yesterday. If you have new information, add it to the existing question instead of starting a new question. – JRE Apr 02 '19 at 06:58
  • But my question is buried deep behind, even if i update, no one will respond – Kutsit Apr 02 '19 at 12:30

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