DS30EA101 Equaliser - Position of input termination resistor

Hi Mike,

a). Please Put the 100 Ohm input termination after the AC coupling Caps as you described.

b). We should also put AC coupling Cap between the 100 Ohm R and the input pins since these are biased internally. Please use 4.7uF Cap for the AC coupling Cap values.

Regards,,nasser

Hi Nassar,

Thanks for your reply, if I understand what you are stating, it is to use four capacitors as shown below:

Is this correct. I am concerned that the self inductance of the extra capacitors may cause a problem, even when using ceramic X5R capacitors.

Regards, Mike.

Hi Mike,

I believe you have the right circuit.

With respect to the self inductance, normally we use only C83 and C84 but given your requirements we have to add C85 and C86 as well. We can try to minimize the self inductance by placing these passive components right close to one another and close to the device. Based on past experience, up to 3Gbps we have not seen issue with self inductance.

Regards,,nasser

Adding one note - depending on what coding your data has, you may be able to get away with smaller size caps than the 47uF that are shown.   As a rule of thumb, the RC time constant should be much larger than the longest run with no transitions that your coding allows. If your data is 8b10b encoded, for example, then you could use muich smaller caps.

^{Thanks everyone for your suggestions very helpful, I shall now test the circuit.}