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DS90UB948-Q1: DS90UB948-Q1

Tomas Redelius
Prodigy 40 points
Part Number: DS90UB948-Q1

Hi.

We are using DS90UB948 with DS90UB941.

We also use Power over Coax (not differential).

We have used the TI information on POC for FPD Link III for cameras as the display circuits miss this information:

The picture is transfered without problem but the back channel/configuration channel are very disturbed. The I2C link hardly works. 

Soo some questions:

1) Is the POC filter recommended for FPD-Link III camera side also valid for the display link.

2) I can not find information of the frequency range used for the back-channel. We need to understand the dimensioning of the POC filter and critical frequencies.

3) 10uH is recommended for camera side. Is this valid for the display link?

4) The deserializer have an equalizer function to adapt to long/aged cables. Does the  serializer have this function for the back channel?

BR

   Tomas Redelius

    Stoneridge Sweden

  • 0
    TI__Genius 11340 points

    Hi Tomas,

    Whether you can use the camera PoC network depends on a few things:

    - The power you are planning to draw

    - The forward channel frequency (for 941 single link mode, it's 35 * f_PCLK)

    - The back channel frequency (set from the 948)

    Could you provide me with the above information?

    To answer your last question, the serializer doesn't have the equalizer for the back channel because it's at a lot lower speed.

    Best,

    Jiashow

  • 0 in reply to Jiashow Ho
    Prodigy 40 points

    Power;  300mA and 35V

    Pclk: 74MHz

    Back channel 20Mb/s

    Soo question:

    Soo some questions:

    1) Is the POC filter recommended for FPD-Link III camera side also valid for the display link.

    2) I can not find information of the frequency range used for the back-channel. We need to understand the dimensioning of the POC filter and critical frequencies.

    3) 10uH is recommended for camera side. Is this valid for the display link?

    4) The deserializer have an equalizer function to adapt to long/aged cables. Does the  serializer have this function for the back channel?

    BR

       Tomas

  • 0 in reply to Tomas Redelius
    TI__Genius 11340 points

    Hi Tomas,

    All the PoC testing we've done have been on the ADAS side. 35V POC voltage is quite high. For our ADAS devices we typically recommend 9 -12V only. You would need to make sure the cable is able to withstand 35V and that it won't disturb the link.

    1) Is the POC filter recommended for FPD-Link III camera side also valid for the display link. It won't be. The PoC network for the ADAS devices on the datasheets can only support up to 250mA.

    2) I can not find information of the frequency range used for the back-channel. We need to understand the dimensioning of the POC filter and critical frequencies. The PoC network needs to be able to filter the back channel frequency all the way up to the forward channel frequency. The back channel frequency is set from the 948 side and can be 5Mbps, 10Mbps, or 20Mbps.

    3) 10uH is recommended for camera side. Is this valid for the display link? 10uH on the camera side is used to filter 50Mbps back channel. Since the back channel on the 948 is lower, you might need a bigger inductor (100uH) to filter out the back channel frequency.

    4) The deserializer have an equalizer function to adapt to long/aged cables. Does the  serializer have this function for the back channel? No. The back channel is at a lot lower speed. The serializer doesn't need adaptive equalization.

    Best,

    Jiashow

  • 0 in reply to Jiashow Ho
    TI__Genius 11340 points

    Hi Tomas,

    I see you clicked on this did not resolve my issues. Do you have any additional questions that I can answer?