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Differential input accepting single ended signal

ahtran

I am using the ADN2917 differential output as single ended inputs into the HMC856 and HMC726.  The system is communicating at 10Gbps.  I don't have the option of using a clock buffer.  Can the circuit be connect like below? 



Adding note about the clock buffer
[edited by: ahtran at 7:30 PM (GMT -4) on 28 Apr 2021]
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  • 0
    •  Analog Employees 
    on Apr 29, 2021 6:25 AM

    Hi Ahtran,

    Differential ADN2917 output specs are different from single ended HMC856 and HMC726 devices. You will need to review the VIH/VIL specs for chip being driven by the ADN2917 in differential mode wrt single-ended spec from HM856 and HMC716. We can connect to one single ended device at a time but it violates the spec when we connect to two single ended devices. In general AIN+ can be used for single ended operation, check the HMC726 datasheet for the connectivity.

    Thanks,

    Siva Kumar.

  • 0 on Apr 30, 2021 3:23 PM in reply to ADIApproved

    Hi Siva,

    I have another question.  If I want to connect the output of ADN2917 to the input of HCM856, can I use DC couple connection as shown below?  The ADN2917 is using a positive voltage rail, but the HMC856 is using a negative voltage rail, so I am not sure if DC couple is possible.

    If AC couple is required, do I need to add 50 ohm pull-up to VCC on the ADN2917 side?

    Thanks

  • +1
    •  Analog Employees 
    on May 3, 2021 5:13 AM in reply to ahtran

    Hi Ahtran,

    Yes, you are right. DC coupling connectivity is not possible at the output section in this scenario and external pull-up required at output circuitry. AC coupling capacitors and pull-up resistors are must to be chosen such that the device should work properly without effecting the full data rates. Please refer to the applications information section in ADN2917 data sheet for choosing AC Coupling Capacitors.

    Regards,

    Siva Kumar.

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  • +1
    •  Analog Employees 
    on May 3, 2021 5:13 AM in reply to ahtran

    Hi Ahtran,

    Yes, you are right. DC coupling connectivity is not possible at the output section in this scenario and external pull-up required at output circuitry. AC coupling capacitors and pull-up resistors are must to be chosen such that the device should work properly without effecting the full data rates. Please refer to the applications information section in ADN2917 data sheet for choosing AC Coupling Capacitors.

    Regards,

    Siva Kumar.

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