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DS100BR410: How to understand the minimum input voltage swing 600mV

Yuxi Liu(Tony)
Expert 3310 points
Part Number: DS100BR410
Other Parts Discussed in Thread: DS25BR100,

Tool/software:

Hi TIer

My medical customer saw this parameter in the data sheet, the minimum input voltage needs to be 600mV.

But when customers need a redriver, the signal is very attenuated much less than 600mV.

So we're confused here about what this parameter really means.

Also How SDH and VTX should be understood ?

Thank you very much.

same question in DS25BR100

The datasheet mentioned similar, the input voltage threshold needs to be minimum 100mV, but the received eye figure closed amplitude is generally less than 100MV, so how should this VTH100mV be understood?

  • 0
    TI__Mastermind 28500 points

    Hi Tony,

    V_TX(min) = 600mVpp is the recommended source transmit launch amplitude at TPA. The signal amplitude is attenuated from passing through Media A before reaching the device Rx pins.

    The signal detect thresholds control if the channel output is on or off. Channel output is turned on when the amplitude at the Rx pins is at least 130mVpp. Channel output is turned off when the amplitude falls below 60mVpp. These thresholds are configurable via SMBus registers.

    Regarding DS25BR100, V_TH and V_TL specify the min and max amplitudes which guarantee a "high" or "low" output. If IN+ minus IN- is greater than +100mV, the device is guaranteed to output "high." If IN+ minus IN- is less than -100mV, the device is guaranteed to output "low."

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    TI__Expert 3310 points

        1  If source amplitude 600mV VPP, RX  PIN amplitude need >130mvpp.So the channal loss can only support 20log(600/130)=13.255dB@Nyquist freq, right? please double check

       2  DS100BR410  input is CTLE ，the device rx pin's eye diagram is closed ,  the CTLE is passive, why there need the least amplitude 130mV,please double check

       3  DS100BR410's  architecture is CTLE+DRIVER ,the least amplitude 130mv should at the point after CTLE,not at the point of the device RX pins, please double check

      4 NOW the TX DRIVER output  amplitude is 200mV,if use DS100BR410 to redriver the singnal ,now how to calculate the max channel loss.

  • 0 in reply to Yuxi Liu(Tony)
    TI__Mastermind 28500 points

    Hi Tony,

    1. DS100BR410 can apply up to 37dB boost @ 5.5GHz with SMBus control.

    2. Channel output is muted or unmuted by the signal detect block. The purpose is to prevent noise from getting amplified and output through the device.

    Note that there is a difference between the peak-to-peak signal amplitude and the eye height. The signal detect thresholds are compared to the peak-to-peak signal amplitude, so a closed eye signal with >130mVpp amplitude will pass through the device.

    3. You're correct, the signal detect block exists between the CTLE and the limiter. Signal amplitude is checked at this point.

     

    4. The max insertion loss on the Tx side of the redriver is dependent on the EQ capability and amplitude requirement of the connected receiver device. DS100BR410 can apply up to -9dB of de-emphasis which can help to equalize the signal on the Tx side at the expense of attenuating the signal. It is difficult to quantify how much reach extension can be achieved by de-emphasis.

    In general we recommend placing unidirectional redrivers close to the receiving end of the link. This is because the majority of equalization is applied on the Rx side of the redriver.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 20 points

    Hi Lucas,

       TKS for your reply. About the issue of peak-to-peak signal amplitude and the eye height.I have two question:

    1 If i need to evaluate the signal@ input pin of DS100BR410.How to  evaluate  the closed eye diagram whether meet the requirement of  DS100BR410.

    2  The signal of closed eye diagram contain signal with >130mv  and <130mv,DS100BR410 how to judge whether pass or not.

    Best,

  • 0 in reply to jie yang
    TI__Mastermind 28500 points

    Hi Jie,

    1. To check if the input signal meets the signal detect threshold, measure the peak-to-peak amplitude of the signal at the DS100BR410 receiver and check if it is larger than the signal detect assert threshold. With default configuration, the signal detect assert threshold is 130 mVpp.

    2. I believe you are saying the peak-to-peak amplitude of your signal is larger than 260mVpp at the DS100BR410 receiver. This is significantly larger than the signal detect assert threshold and the channel output will be unmuted.

    Best,

    Lucas