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DS25BR110: Optimum device choice for 1.6 Gbps LVDS twinax cable extension driver/receiver question

Mitchell Kary
Intellectual 630 points
Part Number: DS25BR110
Other Parts Discussed in Thread: DS30EA101, , DS15BA101, DS25BR120, DS30BA101, DS15EA101

Hi,

I am looking for guidance on selecting either a DS15BA101/DS15EA101, DS30BA101/DS30EA101 or DS25BR110/DS25BR120 solution to drive a 25 foot twinax 100 ohm cable serdes link running at 1.6Gbps. Is there a specific advantage to any one of the above choices such as adaptive vs select-able EQ or performance in general?

Thanks,

Mitch

  • 0
    TI__Guru* 88835 points

    Hi Mitch,

    DS30EA or DS15EA have a higher gain - ~40 dB at 800MHz(1.6Gbps Nyquist). It all depends on the loss of you cable. If it has higher loss then perhaps EA would be a better option. Also, EA devices are adaptive so overall this could be a better option.

    Regards,Nasser 

  • 0 in reply to Nasser Mohammadi
    Intellectual 630 points

    Hi Nassar,

    Thanks for the reply. So if I consider the adaptive options, is there a reason to use or not use the DS30BA/EA vs the DS15. I have 2.5V available. Also does the adaptive EQ help with any other issues besides straight cable loss such as small impedance discontinuities due to twinax connector to connector junctions?

    -Mitch

  • +1 in reply to Mitchell Kary
    TI__Guru* 88835 points

    Hi Mitch,

    DS30 is a later version versus DS15 so if possible DS30 would be a better option.

    None of the parts noted in this case address impedance discontinuity. This causes return loss issue and these parts are equalizers and do not address reflection or impedance discontiuity. You can optimize your layout or simulate to reduce impedance discontinuity. Typically at this low data rate perhaps you can get away with some impedance mis-match. Unfortunately you have to either simulate or build a board to verify this.

    Regards,Nasser

  • 0 in reply to Nasser Mohammadi
    Intellectual 630 points

    One more follow-up question about using DS30BA101. Should I be providing any sort of power supply filtering other than a bypass capacitor to minimize potential jitter from Vcc? Also is there an equation relating RVo to Output amplitude? Is the jitter from the DS30 better or same as DS15BA101 device?

    Thanks,

    Mitch

  • 0 in reply to Mitchell Kary
    TI__Guru* 88835 points

    Hi Mitchell,

    1). Normal bypass Cap is good enough. Please note DS30BA101 is like analog buffer.

    2). Please refer to the data sheet. Typically you should be able to move output amplitude by 5 to 10% of the default values - using RVO Resistor.

    3). From additive jitter point of view, DS30BA would be a better option - ~10-15PS lower than the DS15BA101

    Regards,Nasser