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How to simulate the common mode return loss for LVDS driver?

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poyu

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common mode return loss

I am studying the LVDS driver. However, I don't know how to check the common mode return loss performance by hspice. I tried to use ac analysis to find ZIN first. Then, using the formula for reflection coefficient to get the return loss.

Γ=(Z2-Z1/Z2+Z1) Z2: 45ohm cable impedance Z1: ZIN from ac analysis

Finally, transferring the value of reflection coefficient to dB for common mode return loss.

I am not sure the answer is right or not.


My spice code to get ZIN:

vref vref 0 0.75 *0.5VDD
vac TDP TDN ac=1
xpkg1 TDP RP *RLC for package bonding wire load
xpkg2 TDN RN *RLC for package bonding wire load
RT1 RDP 0 45 *45ohm termination in RX
RT2 RDN 0 45 *45ohm termination in RX

.net vac
.ac dec 20 10 10G
.probe ac zin
 

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