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DS90UB925Q-Q1: Replace DS90UB921 with DS90UB925 to pair with DS90UB940

JPAlleyne
Expert 1565 points
Part Number: DS90UB925Q-Q1
Other Parts Discussed in Thread: DS90UB940-Q1, DS90UB927Q-Q1

I posted the following in this forum a while ago about pairing DS90UB921 with DS90UB940 :

https://e2e.ti.com/support/interface/f/138/t/790309

I am not too sure how well the with DS90UB921 is being distributed (discontinued at digikey non stock in Mouser). Long story short, I am wary about using the part in design. Based on the forum post above:

1) Is there anything I have to be worried about by using the with DS90UB925 instead of the with DS90UB921 with the with DS90UB940?

2) On page 26 of the UB940 it says: Note: if paired with a DS90UB925Q-Q1serializer, the devices must be configured into 18-bit mode to allow usage of GPIO pins on the serializer. Does this mean I would not be able to use the GPIOs on the serializer if I'm doing 24-bit?

3) On page 31 of the UB940 it says: The DS90UB940-Q1 is also backward compatible to the DS90UB925Q-Q1, DS90UB925AQ-Q1, and DS90UB927Q-Q1 for PCLK frequencies ranging from 25MHz to 85MHz. Does this mean I can't use the full range of the UB25 (5 to 85MHz) when paired with the UB940? My sensor does 13.5 MHz or 27 MHz only... if this is the case I'll have to use 27 MHz?

4) Why is the distribution of the UB921 so unorthodox?

Thanks,

JP

  • 0
    TI__Guru** 103215 points
    Hello JP,

    1. The main difference between 925 and 921 is the pixel clock range. 925 can support up to 85MHz, while 921 can support up to 96MHz. Other than that there should be no major concerns using 925 or 921 with 940.

    2. That is correct. The GPIO pins are shared with bits on the 24 bit RGB interface on the 925 and 921.

    3. This is also correct. 940 requires a minimum 25MHz PCLK, so the available range when using 925 is 25-85MHz PCLK

    4. Please contact your local distribution partner or TI sales team for assistance sourcing the device. On our TI store I can see that there are units available for direct purchase as well.

    Best Regards,
    Casey
  • 0 in reply to Casey McCrea
    Expert 1565 points

    Sorry, for the late reply. Sometimes I don't get the email notifications from TI. Thank you, you've answered my questions. Since there is no big difference, I think I'll stick with the 925 since I wouldn't need that high of a pixel clk.

    Thanks,

    JP