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ADV7623 evaluation board impedances

Question asked by drv11 on Sep 10, 2013
Latest reply on Sep 11, 2013 by GuenterL

Hi All,

 

I've just been going over the pcb layout of the ADV7623 evaluation board. I've been informed the trace impedance for the TMDS signals should be 50 Ohm and differential impedances of 100 Ohms. According to the PADS layout viewer, the trace impedances on the ADV7623 are 84 Ohms. That gives me a differential impedance (at 0.1666mm spacing, 0.1466mm trace width) of ~125Ohms. Is the discrepancy here due to the PADS calculated value only being for the traces and ignoring impedance effects from the pads of the IC/HDMI connector? If not, why are these so different to what is specified?

 

Thank you for your time.

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