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DS90UB914A-Q1: link problem

Annie Liu
Genius 10295 points
Part Number: DS90UB914A-Q1


Hi Team,

Customer has below questions need your help:

1. The main can communicate with the near-end 914 for I2C, and can read the address of 913 from the 0x06 register, but there is no ACK signal for communication with 913.

2. After power-on, the lock pin and pass pin of 914 flicker. The lock pin level measured with an oscilloscope is shown in the figure below:

The conditions are:

1. The 913 terminal has passed the 954 verification and the map;

2. The circuit diagram of the 914 terminal is as follows:

3. The pin configuration of 914 is:

4.The register configuration of 914 is:

0x03 register write 0x0D, auto ACK; 0x21 write 0x97;

Thanks,

Annie

  • 0
    TI__Genius 11340 points

    Hi Annie,

    It looks like lock is unstable. I have a couple of comments:

    - There's no decoupling on the VDD18 rail? Make sure the decoupling caps match the datasheet recommendations and the supply noise meets the requirements.

    - Check the 913 PoC network to make sure it has 100uH inductor.

    -  Use CMLOUT pins to check the received signal. If signal looks bad, try manually adjusting the EQs and check the impedance/s-parameter of the board.

    Best,

    Jiashow

  • 0 in reply to Jiashow Ho
    TI__Genius 10295 points

    Hi Jiashow,

    The VDD18 signal has been measured by an oscilloscope, without noise;

    913’s POC network has an inductance of 100uH;

    The CMLOUT pin signal was tested, as shown in the figure below:

    Customer would like to know how does he manually adjust the equalizer?

    Best Regards,

    Annie

  • 0 in reply to Annie Liu
    TI__Genius 11340 points

    HI Annie,

    What was the noise measured on the VDD18? Did the customer add decoupling caps?

    The customer should use a differential probe to check CMLOUTP and CMLOUTN pins. THey should see an eye diagram, not a DC voltage. They can bypass AEQ in reg 0x4D and manually set it in reg 0x04.

    Best,

    Jiashow

  • 0 in reply to Jiashow Ho
    Prodigy 20 points

    Hi Jiashow,

    The lock is still unstable since I've tried these suggestions.

    signla of CMLOUT pins looks bad as follows:

    BTW, the same 913-module works well with another board witch uses 954 for DES.

    best

    Tianyu

  • 0 in reply to Jiashow Ho
    Prodigy 20 points

    Dear Jiashow,

    We don't have differential probe. there seems to be no noise on the VDD18.

    I tried to bypass AEQ and adjust the value of 0x04, the phenomenon keeps the same.  

    I will ask my hardware engineer to  check the impedance/s-parameter of the board first,and then refer to U for more help.

    Tianyu

  • 0 in reply to tyhuang
    TI__Genius 11340 points

    Hi Tianyu,

    Measuring the impedance/s-parameters work as well, but first I'd like to verify the noise spec with them. 

    What was the noise measured on the VDD18? Did the customer add decoupling caps according to the datasheet spec? What decoupling caps did they add?

    Jiashow