External circuit for embedded A2D module test

Discussion in 'The Projects Forum' started by mahfuz, Feb 23, 2008.

  1. mahfuz

    Thread Starter New Member

    Feb 23, 2008
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    Guys,

    Would someone kind enough to share a full-complete ramp circuit design that can ramp up precisely from 0V up to 6.5V for the purpose of ADC testing? Its more into A2D since the test is for embedded ADC module testing inside a chip, not on a normal ADC device. I have tried for so long but didnt even get the circuit right.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    It is best if you create your own thread. This highlights your question so that members can focus on your specific problem and it also avoids disruption of the existing thread.

    For these reasons, I have moved your post to its own thread.

    hgmjr (moderator)
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    How precise does it have to be?
    How long should the ramp be, time-wise?
    What about the falling edge? Does it also need to be a ramp, or should it be fast?
    Does the ramp need to be buffered, or can you drive the A/D from a high impedance?
     
  4. mahfuz

    Thread Starter New Member

    Feb 23, 2008
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    The positive ramp should be from 0V up to 6.5V and the frequency can be controlled. Its hard to have an analog design to control the frequency of the rising edge of the ramping voltage. The falling edge need to be as fast as possible so that it could be ready for a new ramping voltage at another clock cycle.

    In terms of frequency drive, it should be operated at any frequency level up to around 50MHz (for tester usage).
     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Dream on.:rolleyes:
     
  6. scubasteve_911

    Senior Member

    Dec 27, 2007
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    The only way I can think that can do this simply is to use a Direct digital synthesizer. Or, If you can get a variable frequency clock to run a free-running counter, then output that to a parallel input DAC, then use a low-pass filter, you may be able to get a decent waveform.

    If you understand how this is done in the analog domain, you will know that it is nearly impossible. And if it were possible, it wouldn't be a simple implementation!

    Steve
     
  7. scubasteve_911

    Senior Member

    Dec 27, 2007
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  8. mahfuz

    Thread Starter New Member

    Feb 23, 2008
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    i have checked on it and the problem is that it doesnt start from 0V.
     
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