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DS280DF810: DS280DF810 eye open monitor feature

Gabriel Xu
Intellectual 2145 points
Part Number: DS280DF810


Tool/software:

Hi Team

Customer have few questions when using DS280DF810 in their new design:

1) For eye diagram monitor register 0x27/0x28, it only return measure value when the CDR is locked right? If the CDR is not locked what will we read back from this register?

2) Customer want to know do we have minimum value for 0x27/0x28 register read back value to ensure CDR could be lock?

3) Customer feedback that they used this device in QSFP18 100G optical module and found these two register is much lower than the design in 40G QSFP+ they want to know why?

  • 0
    TI__Mastermind 37333 points

    Hi Gabriel,

    Is it possible for the customer to share a channel register dump?  Also, can you share block diagram of the customer's system.

    1. Yes, this is correct.  If CDR is not locked, the data you read back is not valid.
    2. There is not a minimum value for CDR lock, but for good BER performance, we have empirically observed that HEO/VEO should be >= 0.4UI, 200mV.
    3. What values are they reading?  40G QSFP uses 10G signaling, while 100G QSFP uses 25G signaling.  It is common to observe better eyes at 10G due to lower speed.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    TI__Intellectual 2145 points

    Hi Drew

    For good BER performance you means that we recommend to have HEO>0.4UI and VEO>200mV right?

    For 25G QSFP 0x27=0xe and 0x28=0x40

    For 10G QSFP 0x27=0x1e 0x28=0xc0

    To ensure BER performance we only have sperate requirement for HEO and VEO value but didn't have requirement for eye wide and height ratio? 

  • 0 in reply to Gabriel Xu
    TI__Mastermind 37333 points

    Hi Gabriel,

    Gabriel Xu said:
    For good BER performance you means that we recommend to have HEO>0.4UI and VEO>200mV right?

    Yes, this is correct.

    Gabriel Xu said:
    To ensure BER performance we only have sperate requirement for HEO and VEO value but didn't have requirement for eye wide and height ratio? 

    I don't understand your question, can you please clarify?  Registers 0x27, 0x28 contain HEO and VEO.

    Gabriel Xu said:

    For 25G QSFP 0x27=0xe and 0x28=0x40

    For 10G QSFP 0x27=0x1e 0x28=0xc0

    Based on these measurements, the customer is meeting our recommended minimum HEO/VEO requirements.

    0x27 0x28 HEO VEO
    0x0e 0x40 0.4375 200
    0x1e 0xc0 0.9375 600

    Can you please share a block diagram of the customer's system?  Can the customer adjust the TX FIR settings of the signal being sent to the retimer to help improve 25G eye?

    Thanks,

    Drew