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CDCM61004: CE pin as reset trigger?

Tomasz Wlostowski
Prodigy 10 points
Other Parts Discussed in Thread: CDCM61004, TMS320C6657

Does toggling the CE pin of CDCM61004 trigger a full power down-power up cycle of the device, including VCO calibration? The RST pin is floating in our case and we have only control of the CE pin in our design...

Best Regards,
Tomasz Włostowski
  • 0 in reply to Madhu Balasubramanian
    Expert 1162 points
    Dear All,

    on our own board the toggling of CE does not trigger the VCO calibration procedure. It is needed to use the RSTN pin for that. The CE pin disables only the outputs.

    It is also recommended to use the RSTN pin for explicit power-on reset because in some cases the internal POR does not work, specialy in case of fast power switch-off and switch-on.

    Kind regards
    Sven
  • 0 in reply to Sven Mulka
    TI__Expert 4400 points

    The CE pin disables output and certain parts of the device but not the PLL and doesn't trigger re-calibration of VCO/PLL. The RSTN pin is needed to achieve this.

    Can you use RSTN?

  • 0 in reply to Madhu Balasubramanian
    Expert 1162 points

    Dear Madhu,

    thanks for your confirmation of the behaviour. I had reply to this old thread for clarification only. 

    Unfortunately we have no connection to the RSTN pin, here is only a connection to the CE pin on the board. As workaround I am using an additional wire to the RSTN pin as explicit reset of device.

    For your information, we are using the CDCM61004 as clock generator for TMS320C6657. It transfers the 25 MHz clock to 156.25MHz, which is used for DSP and also for SGMII SerDes.

    The behaviour of the CDCM61004 is a little bit strange. After the first power-on sequence the CDCM61004 works fine and it looks like that the internal POR runs the VCO calibration.

    After a short or longer (1s to 20s) power-off followed by power-on the internal POR does not run the VCO calibration correctly on my board. As result the output clock is around 170 MHz instead 156.25 MHz. In that case the SGMII SerDes does not work correctly and the RBL does not work in Ethernet Boot mode.

    I am writing this to help other users during the troubleshooting.

    Kind regards
    Sven