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Output sawtooth wave to AD9144

This is a question about the operation of the AD9144.
My customers are evaluating the AD9144.
My customer is trying to output sawtooth waves from AD9144.
T = 200 nS, + 100 count → -100 count
The customer inputs the code and evaluates the output waveform.
Strangely, the output slope bounces small around 0 count.
Customers suspect this as miscounts.
Is this due to the nature of T-DAC?
Do you have any views?
Please advise me.

 

Is this phenomenon called MIDSCALE GLITCH?
Where should I check to isolate it from mistakes in circuit design?

Best regards

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  • Hi Mochi,

    My guess is the issue is related to the point in the vector where all 1's trnsition to all 0's.

    likely a load regulation issue on the digital supply. Consider checking the digital supplies during the transition on a scope, comparing against the DAC output: it is possible the issue is simply to the available charge during the transition, in which case adding a bulk capacitance (say 10-20uF) near the DAC could help.

    If a scope isn't available, an interesting test would be to compare data vectors that are 2's complement vs. unsigned. In this case the glitch should move by a few samples. The data format is configurable at the AD9144:

    this would simply confirm the issue, not fix it.

    Was the issue noted on an AD9144 EVB, or was it on the customer's board?

    Best Regards,

    Arik

Reply
  • Hi Mochi,

    My guess is the issue is related to the point in the vector where all 1's trnsition to all 0's.

    likely a load regulation issue on the digital supply. Consider checking the digital supplies during the transition on a scope, comparing against the DAC output: it is possible the issue is simply to the available charge during the transition, in which case adding a bulk capacitance (say 10-20uF) near the DAC could help.

    If a scope isn't available, an interesting test would be to compare data vectors that are 2's complement vs. unsigned. In this case the glitch should move by a few samples. The data format is configurable at the AD9144:

    this would simply confirm the issue, not fix it.

    Was the issue noted on an AD9144 EVB, or was it on the customer's board?

    Best Regards,

    Arik

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