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ESD Protection on the Dout Pins of FPD-Link Serializers

Joe Howard
Intellectual 2970 points

One of my customers are using TVS Diodes on the Dout pins (the are using them on the 927, 947, and 949), which I’m guessing is for ESD protection.

Will these impact performance? (I didn’t think they needed these since the Dout pins already have ESD protection.)

I also assume this will impact the impendence of the HS lines and possibly cause reflections a degrade performance (add loss).

Is this the case?

Should they remove these from their design?

  • 0
    TI__Expert 5210 points
    Hello Joe,

    These diodes are not necessary but can certainly improve system ESD performance, but also reduce signal integrity on the high speed lines. In order to properly use them, make sure that the customer places one pad of the footprint of the diode on the trace itself to minimize the impedance discontinuity/stub. The trace connected to the diode should be as short as possible and the TVS diode connected should be for high-speed applications - i.e. very minimal capacitance in the 1-2pF range or lower.

    You will see less degradation of link performance on 927 then you will on 929 and 949 due to a slower high-speed data line rate for 927 device.

    -Sean