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DAC3482 Drive problem

DeeJay
Intellectual 840 points

Other Parts Discussed in Thread: DAC3482, LMK04828

Hi,

Attached is a simple block diagram re DAC3482 drive issue from a customer of ours.

The customer is using the DAC3482 in a non-standard way, because they need to use gated (non-DC balanced) signals on the DACCLK and OSTR pins. The datasheet requires AC coupling this signal which they therefore cannot do.

The ? is the circuit in question on the attached that cannot be a capacitor as the DACCLK and OSTR cannot be DC balanced signals in their application.

They tried with LVPECL buffers using negative supplies as the ground to level shift the signals but this approach has fallen through.

Could anyone assist here to resolve this issue?

Thanks.

DAC Drive Problem.pdf
  • 0
    TI__Guru* 82545 points

    Hi Deejay,

    DC coupling the DACCLK and OSTR receivers should not be a problem. The -0.2V to 0.6V of swing per leg creates 0.2V of common voltage and 0.8Vp differential swing. This is within the DAC receiver specification as well.

    We have a few customers implemented this approach successfully. We also use DC coupling on our production site as well to test both the DC common and AC swing.

    I am not sure about your symbol for "?" Please advise if they are asking what circuits are needed for the translation. On some of our newer clocking devices such as the LMK04828, the LCPECL driver type can be used for DC coupling approach. You can ping the clocking team forum for more detail.

    It will be helpful if the customer can describe the exact issue. You may also refer the customer to the following app note for configuration guidance.

    http://www.ti.com/lit/an/slaa584/slaa584.pdf

    -Kang

  • 0 in reply to Kang Hsia
    Intellectual 840 points

    Hi Kang,

    Thanks for your response. I will pass the message to the customer.

    The "?" symbol on the block diagram is for the required circuits or a suitable component(s) that TI could recommend.

    Meantime, I will get more details about the issue.

    Rgds,

    DJ