SN75DP159: Case_GND and GND connection

Kenji-san

The RC between the board ground and the case ground prevents potential noise from the board ground being coupled on the shield ground. And if a cable is connected, then the cable will act as a antenna and create EMI radiation.

So the question of connecting the case ground and the board ground is more a system design consideration. I would recommend reading up Henry Ott's book Electromagnetic Compatibility Engineering for more detailed info.

Thanks

David

Hi David,

Thank you for your answer.

Can you answer my other question as well?

I would like to know the problem when connecting directly without RC.

Best Regards,

Kenji

Kenji-san

Please refer to my first paragraph in my response, you could have an EMI issue depending on how much noise is being coupled from the board ground to the shield ground if they are connected together.

Thanks

David

Hi David,

I understand. Thank you very much.

Isn't the RC connection between Case_GND and S_GND a measure for surge inside the application?

Best Regards,

Kenji

Kenji-san

Could you please elaborate on the surge measurement inside the application?

Thanks

David

Hi David,

I didn't measure the surge, but HPD_SNK(28pin) short and SCL_SNK(32pin) leaked, so I'm looking for the cause.

There is a difference between Case_GND and S_GND so I would like to know how this affects.

Best regards,

Kenji

Kenji-san

This looks to be a separate issue, do you have the monitor connected when you are seeing this leakage on the HPD_SNK and SCL_SNK? If the monitor is plugged in, does this leakage go away when the monitor is unplugged?

Thanks
David

Hi David,

This is caused by the inspection of the IC itself, so the IC is destroyed.

I suspect external ESD. I know the measures to attach TVS diode.

I noticed the difference in the connection method of CASE_GND and S_GND of the reference, and asked a question in this thread.

If this connection is a different issue than ESD, I understand that.

Best Regards,

Kenji