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DIR9001: No DOUT data output, ERROR

Adrian
Prodigy 10 points

Part Number: DIR9001

Hello,

I am trying to use the DIR9001 in PLL-only-mode, according to the schematics below.

When I apply an optical signal to my TOSLINK receiver, the PLL locks, and I get valid outputs on FSOUT0/FSOUT1, depending on the input format. I tried with 44.1 kHz and 48 kHz inputs, and in both cases the LRCLK and the BCLK are generated correctly. However, I never get any DOUT signal (always low -> MUTE). The ERROR pin is high, so there is probably some parity/data error, since the PLL locks fine.

What could be wrong? The optical sources work fine with other equipment.

Thanks in advance

  • 0
    Prodigy 10 points

    Found the problem: I am missing a reset circuit. It seems to be required.

    Removing the pullup on the reset pin resolved the issue. Is that a reliable solution, or should I use an external reset generator?

  • +1 in reply to Adrian
    TI__Mastermind 23050 points

    Hi Adrian,

    The DIR9001 has an internal 51kOhm pullup on the RST line, so it is not typically required to pull it up externally as well. However it is recommended in the datasheet to toggle the reset after powerup: "The reset operation must be performed during the power-up sequence as shown in Figure 4. Specifically, the DIR9001 requires reset operation with a 100-ns period after the supply voltage rises above 2.7 V."

    Best,

    Zak

  • 0 in reply to Zak Kaye
    Prodigy 10 points

    Hi Zak,

    thanks for clarifying, I will add a reset generation circuit for the next revision. With only the internal pull-up in place, the part seems to start up reliably, but I cannot be fully certain.

    Best regards,

    Adrian