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DS280MB810: Graphs Of Gain Transfer Function

Daniel Jackson
Intellectual 575 points
Part Number: DS280MB810
Other Parts Discussed in Thread: DS280BR810

In the DS280MB810 datasheet (SNLS542, October 2016), the graphs on p. 13 in Section 6.7 show the gain transfer functions.  The input differential peak-to-peak voltage is shown down to only about 250mVdpp, implying that the part may not properly handle input signals of smaller amplitude.

However, Tables 7, 8 and 9 on p.41-43, indicate 25.8Gbps input signalling being passed through input transmission lines having losses of 14dB and 22dB, which would result in input amplitudes far less than 250mVdpp.

How small an input signal will the device handle (ignoring such issues as squelch detect)?  If less than 250mVdpp, why do the gain graphs not illustrate teh behavior for lower input amplitudes?

  • 0
    TI__Mastermind 19235 points

    Hi Daniel,

    Your assumption based on datasheet plots is not correct. Though 250mVpp was the lowest measured value for these plots in question, it is not the minimum amplitude sensitivity level for this redriver.

    For its default settings the effective operational minimum Rx amplitude is the minimum signal detect assert level of 196mVpp listed on the datasheet. However, lower input amplitudes may be supported by forcing signal detect HIGH via channel register write. Based on our validation results the DS280MB810 can support voltage input differential (VID) down to 150mVpp measured at the device inputs with negligible performance degradation.

    Cordially,

    Rodrigo Natal

    HSSC Applications Engineer

     

  • 0 in reply to Rodrigo Natal
    Intellectual 575 points

    Rodrigo,

    Thanks for your response.

    So, what would the gain function look like graphically between 150mVdpp and 250mVdpp; what gain (as a function of the gain mode and VOD setttings) could be expected?

    Please also answer same regarding the DS280BR810.

  • 0 in reply to Daniel Jackson
    TI__Mastermind 19235 points

    Hi,

    I do not have this data. You may however extrapolate gain plot down to 150mVpp using the datasheet plot.

    The DS280BR810 and DS280MB810 CTLE are the same, so the same data applies.

    Cordially,

    Rodrigo