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DS90UB935-Q1: What are the application scenarios of the three clock modes？

Sherry Liang
Genius 10255 points
Part Number: DS90UB935-Q1

Dear team,

I also BCC my customer in the BCC list. 

935 has three clock modes, sync mode, non sync external mode and non sync internal mode. My customer wants to know that what the application scenarios of the three clock modes are. In this way we can choose the right clock mode according to different application scenarios.

Thanks & Best Regards,

Sherry

  • 0
    TI__Expert 5480 points

    Hi Sherry, 

    In synchronous mode, the DES provides the reference clock to the SER so the SER does not need its own reference clock. This is the most common use case. In Synchronous mode based on REFCLK input frequency reference, the FPD-Link line rate is a fixed value of 160 × REFCLK. FPD3_PCLK = 4 × REFCLK and Back channel rate = 2 × REFCLK. For example with REFCLK = 25 MHz, line rate = 4.0 Gbps, FPD3_PCLK = 100 MHz, back channel data rate = 50 Mbps.

    In non synchronous mode, the DS90UB935-Q1 uses external reference clock (fCLKIN) the FPD-Link line rate is typically fCLKIN × 80, FPD3_PCLK = 2 × fCLKIN or 1 x fCLKIN and back channel data rate is set to 10 Mbps. For example, with fCLKIN = 50 MHz, line rate = 4Gbps, FPD3_PCLK = 100 MHz, and the back channel rate is 10 Mbps. The sensor CSI-2 rate is independent of the fCLKIN.

    The internal clock has rates similar to the non synchronous clocking mode, but it does  not have the option of CLK_OUT.

    You may check the table " clocking modes" in the datasheet for more explanation on the rates.

  • 0 in reply to Sally Cheung95
    Prodigy 10 points

    Hi Sally,

    We wouldn't like to place an external oscillator. So we prefer Synchronous mode(Mode A) and Non-Sync Internal Clock mode(Mode B). Mode A needs to get reference source from back channel while Mode B use local internal clock. So would you confim the following assumptions?

    1. Mode A needs more time to initialize FPD-LINK and get link lock after system power up.

    2. FPD-LINK in Mode A is less stable than Mode B, which means Mode A requires higher-quality and shorter-length cable.

    Another question for Mode A, since Mode A can be configered as 2Gbps or 4Gbps FC data rate.

    3. For our 1M pixels sensor, 2Gbps bandwidth is enough. 4Gbps Link rate will require higher-quality coxial cable than 2Gbps, right? If that's true, we'd prefer 2Gbps FC data rate.

    Thanks

    Cary

  • 0 in reply to user6489921
    TI__Expert 5480 points

    HI Cary, 

    1. the lock time more related to your cable because for longer/lossier cables, it may take more time for the AEQ circuit to adapt. 

    2. The channel spec (which affects the cable quality/length) is determined by the operating rate.

    3. For lower frequency, the channel specs should be more relaxed. Please have Sherry contact us so we can share the channel specs.

    Thanks, 
    Sally