TLC5947: Input impedance of SPI pins

Hi,

We also don't have the specific input impedance data. As you can see from the figure 12, since input is connected to gate of the FETs, the input impedance should be quite large.

Can you provide more details about the question why there is the requirement of 50 ohms?

Thanks.

Regards,

Kenneth

Thanks Kenneth.  Your assessment is right in line with mine.  I am doing contract work for a company and they are wanting me to reuse previous work from within their organization that seemed to think that the SPI related signals needed to be 50 ohms.  I am doing due diligence to make sure I am not missing something in the previous approach.  Any other input is most welcome.

Sean

Hi, Sean,

Do you know why there is 50 ohms requirement for the SPI? I don't see such kind limitation before.

Thanks.
Regards,
Kenneth

HI Kenneth,
No I do not and that is why I am asking the question in the the forum. I never saw such a need before so I am wondering if I missed something in my understanding of the circuit.
Thanks,
Sean

Hi, Sean,

Do you use long SPI wire? How much frequency do you use?

Regards,
Kenneth

No. Just the normal 30MHz speed.