ADAU1451 output port

Dear sir,

Our customer's project have four serial out from ADAU1451. OUT3 have independent BCLK/LRCK;

for layout board size and EMC concern, OUT1 and OUT2 share BCLK0/LRCK0 from OUT0 (PORT1 and PORT2 BCLK/LRCLK no layout, pin in open state).

Is any risk for this design?


Their class-D amp. not support TDM mode, so they can't use TDM mode design.


By the way, on SigmalStudio setting, they try to set SDATA_OUT1 and SDATA_OUT2 to:

LRCK: Slave from Clock domain 0

BCLK: Slave from Clock domain 0

and expect three OUT have synchronize clock.

But unfortunately SDATA_OUT1and SDATA_OUT2do not output data.


What time should set slave from other clock domain?


Thank you

and

Happy new year!!

  • Dear Dave,

    Thank you very much for your kindly detail answers.

    Sam

  • 0
    •  Analog Employees 
    on Jan 4, 2016 5:27 AM over 5 years ago

    Hello Sam,

    There is a small bug with the output ports. When they are set to master mode, the output port pin does not send the BCLK signal to the other three ports to slave from. This is not true for the LRCLK, it does output a signal for the other ports to slave from so this just affects the BCLK. Since in your case, port 0, is set for master mode, it will be getting its clocks from the internal source. So you have to set output ports 1 and 2 to master mode as well. They will be getting the clocks from the same place so they will be in sync.

    So if you are not using the BCLK pins in the design then yes, it is an EMI concern.

    Suggestion 1:

    It would be a good idea to have a terminating resistor, and they can also set the slew rate and drive strength of the pin to the slowest and lowest settings. I think this is the least risk.

    Suggestion 2:

    The other way would be to run traces from the port_0 BCLK to the Port_1 and Port_2 BCLK pins and set them to slave from their own clock domain. But I would do a full signal integrity analysis of the entire BCLK net to make sure there are not significant reflections and under/overshoot. This will also help prevent any EMI issues.

    So I think suggestion 1 is probably the best solution.

    Happy New Year to you as well!

    Dave T