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DS90UB953A-Q1: DS90UB953A

Tendulkar Selvam
Intellectual 255 points

Part Number: DS90UB953A-Q1

HI,

.Can you tell us how to select the ac coupling capacitor ?? How it is effecting on the FPD3 link line rate ?? is there any formula to use to calculate the AC coupling capacitors ?? or randomly we need to select the capacitors as like for lower frequencies need to select higher capacitors and higher frequencies need to select lower capacitors ??
  • 0
    TI__Guru** 103215 points

    Hello Tendulkar,

    Please follow table 178 in the 953A datasheet for AC coupling capacitor selection. Most commonly customers select 100nF and 47nF for coax configuration in order to ensure the widest compatibility between different devices. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Intellectual 255 points

    HI Casey,

    Thanks for your reply. so how they have selected the 100nF and 47nF , why can't we go with other AC coupling capacitors like 1uF etc. if line rate changes whether will it effect on the coupling capacitor ??

    Regards

    Tendulkar S

  • 0 in reply to Tendulkar Selvam
    TI__Guru** 103215 points

    Hello Tendulkar,

    The AC coupling caps are selected to be small enough to allow the high frequency content of the signal to pass through but large enough to ensure that there is minimal pattern dependent jitter (PDJ) introduced in the signal given longer strings of 0 or 1. Please stick with the recommended ranges in the datasheet as these cap values are validated for the link. For 953A the forward channel frequencies are fixed (4G or 2G) - i.e. they do not vary based on the CSI-2 data input. 

    Best Regards,

    Casey