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DAC5681 DCLK input sequence at power-up

masahiko shimizu
Guru 11235 points
Other Parts Discussed in Thread: DAC5681, CDCM7005

Hi,

Is it possible that DCLK is provide at same time as providing CLK at power-up?
Customer provide DCLK at same time as providing CLK at power-up.

Background of this question is the following.
I posted this question for resolving below issue.

My customer sometime has FIFO_err and DLL unlock at power-on reset.
and DAC5681 output sometime has spurious as below picture.
This spurious continues once this situation is out until power-on reset again.

Best regards,
Shimizu

  • 0
    TI__Guru* 91947 points

    Shimizu,

    Is DCLK have an external 100 Ohm termination resistor near the DAC input? Are both DCLK and CLK generated from the same source? Is DCLK 1/2 the frequency of CLK? Is DCLK driven using LVDS and CLK using LVPECL and terminated with 100 Ohms? What is the setting of the CONFIG10 register? is the input data meeting the setup and hold requirements of the data sheet? What is the frequency of the two clocks?

    Regards,

    Jim

  • 0 in reply to jim s
    Guru 11235 points

    Hi Jim,

    Thank you for your support.

    >Is DCLK have an external 100 Ohm termination resistor near the DAC input?

    [Ans]

    Yes, DCLK have an external 100 Ohm termination resistor near the DAC input.

    >Are both DCLK and CLK generated from the same source?

    [Ans]

    Yes, DCLK and CLK generated from the same source. it is CDCM7005.

    Cusotmer circuit is same as EVM of DAC5681.

    Please see the attached file.

    >Is DCLK 1/2 the frequency of CLK?

    >What is the frequency of the two clocks?

    [Ans]

    Yes, DCLK is 400MHz and CLK is 800MHz.

    >Is DCLK driven using LVDS and CLK using LVPECL and terminated with 100 Ohms?

    [Ans]

    Customer circuit is same as EVM of DAC5681.

    >What is the setting of the CONFIG10 register?

    [Ans]

    Following value is tried. But spurious issue occured.

    0xC0, 0x80,0x90,0xa0,0xb0,0xd0,0xe0,0xf0,0x08

    >is the input data meeting the setup and hold requirements of the data sheet?

    [Ans]

    Customer said Yes.

    DAC5681.pptx  

    Best regards,

    Shimizu