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DAC8564: Only OUTB output voltage change timing is delayed from OUTA/C/D when DAC data are changed from 0000h to 01FFh.

Part Number: DAC8564

Hello guys,

One of my customers is evaluating DAC8564 using DAC8564 EVM for their new products.

In the evaluation, they found that only OUTB output voltage change timing is delayed about 16us from OUTA/C/D one

when all channel DAC data are changed from 0000h to 01FFh. 

When the data are changed from 003Fh to 01FFh, OUTB delay is improved to 1~2us.

Do you know why the delay is happened?

And is there any way to improve the OUTB delay in case of data changing from 0000h to 01FFh?

Or is this phenomenon DAC8564 normal characteristics?

Your reply would be much appreciated.

Best regards,

Kazuya.

  • Hi Nakai-san,

    It usually takes extra time for the op amp to recover when the output is held at one of the power rails. That might be why they see an improvement when the starting code is increased to 0003h. Does the customer have any loads on any of the outputs? Are they seeing any ringing or gross overshoot on any of the channels?

    Best,

    Katlynne Jones

  • Hi Katlynne,

    Thank you very much for your reply.

    They didn't connect any load to VoutA~VoutD of DAC8564 on EVM.

    They just measured VoutA~VoutD at J4A header on the EVM by oscilloscope.

    Also any overshoot wasn't observed at all output.

    Is this phenomenon DAC8564 normal characteristics?

    Thank you again and best regards,

    Kazuya.

  • Hi Nakai-san,

    I am going to check with the designer to see if there are any more details they can share with me. It is expected on any multichannel device that there would be some channel to channel variation. The offset error is given as ±5mV typical in the datasheet. If the offset error is negative for channel B, it could explain why there is a longer delay for that channel.

    I can also send you another EVM and/or a few more samples if you would like to compare the outputs on another device. Let me know if you are interested. 

    Best,

    Katlynne Jones

  • Hi Katlynne,

    Thank you very much for your checking with your team.
    I'm looking forward to receiving the result.

    Also Thank you for your kind words for EVM and device sending.

    I will ask the customer if they need the EVM and device.

    Thank you again and best regards,

    Kazuya.

  • Hi Katlynne,

    Could you please give me your checking result?

    Thank you very much and best regard,

    Kazuya.

  • Hi Nakai-san,

    They confirmed that whenever the output is driven into the rail, additional output recovery time is expected. There could be device to device variations where if the op amp has a negative offset it could make it additionally worse than one with a less offset or even positive offset. The advice would be to avoid starting at code zero. 

    Best,

    Katlynne Jones