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DS125MB203: TX EQ capability

Chi Zhang2
Intellectual 2710 points
Part Number: DS125MB203


Hi, Expert

my customer want to use DS125MB203, as a repeater in the middle of switch chip and optical module. insertion loss @10.3125Gbps, scenario is shown as below.

for switch chip, RX EQ is 15dB

for DS125MB203, TX EQ is 30dB @6.5GHz, while RX max DEM is -12dB.

so my question is do we have any TX EQ capability to cover 3dB loss? Thanks

BR

Chi

  • 0
    TI__Mastermind 36943 points

    Hi Chi,

    Please note that there are several equalizer and de-emphasis settings that can be selected on this device.  I have attached the equalizer settings below for reference.

    Chi Zhang2 said:
    so my question is do we have any TX EQ capability to cover 3dB loss?

    Yes, it is possible to use the EQ settings below in order to compensate for various insertion loss cases.

    With this said, I would recommend running some simulations with your channel and the DS125MB203 IBIS-AMI model in order to better understand if this device will allow you to meet the eye mask requirements for an optical module.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    TI__Intellectual 2710 points

    Hi, Drew

    Thanks a lot for your feedback

    I have misunderstanding DEM, it could compensate through low frequency not like EM to change high-frequency.

    BR

    Chi

  • 0 in reply to Chi Zhang2
    TI__Intellectual 2710 points

    Hi, Drew

    one more question from customer side.

    the typical insertion loss from optical module to repeater is 2.3dB. but our redriver RX has the min limit EQ gain 3dB

    so 2.3dB loss with our RX EQ gain 3dB in typical case could have any over-compensate issue?

    BR

    Chi

  • +1 in reply to Chi Zhang2
    TI__Mastermind 36943 points

    Hi Chi,

    Chi Zhang2 said:
    I have misunderstanding DEM, it could compensate through low frequency not like EM to change high-frequency.

    Yes this is correct.

    At a high level, de-emphasis has some similarities to EQ.  De-emphasis and EQ are two different approaches to solving the same problem, which is that the insertion loss of a transmission medium increases as frequency increases.  EQ compensates for this by boosting the high frequency content of a signal.  De-emphasis compensates for this by attenuating the low frequency content of a signal.  Both of these have a similar effect, which is that the high frequency content of a signal is boosted relative to the low frequency content.

    Chi Zhang2 said:
    so 2.3dB loss with our RX EQ gain 3dB in typical case could have any over-compensate issue?

    I would not expect this to cause any issues since there is still 14.7 dB of loss before the signal reaches the switch chip.

    Thanks,

    Drew