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SN65LV1224B can work at even 4MHz?

Yang Yang8
Intellectual 500 points
Other Parts Discussed in Thread: SN65LV1023A

Hi, all

SN65LV1023A/SN651224B are used as serializer/deserializer in my design. On datasheet it said that they can work from 10MHz to 65MHz. But I found that they can not only work at this frequency range, they can work well at 4MHz.  I really don't know why. Any idea about this?

Thanks

Yang

  • 0
    TI__Prodigy 420 points

    Hi, Yang,

    The range  from 10MHz to 66MHz is internal PLL reference clock range. The input clock signal should have enough

    slew rate to make PLL working. So the chip may work well at low data rate as long as its slew rate meets the request.

    In other words, if you use high swing square signal as the input reference clock, you can use data rate below this range.

    You can also reduce the swing of input clock to check whether the chip still working below this range.  

    Best regards,

    Eric  

  • 0 in reply to Eric Xiong
    Intellectual 500 points

    Hi, Eric

    Thank you very much for your help. And I have reduced the swing of the TCLK pin for LV1023A as shown in the figure below. But still it can work well.(LV1023A can output serial stream, LV1224B can recover clock) 

    By the way, two kinds of LV1224B/LV1023A are used in my design. The one bought couple years ago can not work below 10MHz, but the other one which I get as samples from TI can work at 4MHz. Any relationship?

    BR

    Yang

  • 0 in reply to Eric Xiong
    Intellectual 500 points

    Hi, all

    Does the "new" LV1023A/L1224B get a different PLL reference clock range from the old one? Or some other hints? Any advice will be appreciated.

    Thanks

    Yang

  • 0 in reply to Yang Yang8
    TI__Prodigy 420 points

    Hi, Yang,

    If the device part have the same name, the PLL reference range at datasheet should be same. All chips should be working well in this range. 

    Because of the process variation, some chips may work well at the low data rate out of the range,while some may not. So If you want use the data rate below this range, there may be some risk.

    Regards,

    Eric