DS90C385A: DS90C385A : Insertion the damping resistor to TxCLKOUT+/TxCLKOUT

Michi Yama

Guru 10030 points

Part Number: DS90C385A

Hi,

I have one question regarding TxCLKOUT+/TxCLKOUT- pin of DS90C385A.

My customer would like to insert the damping resistor to TxCLKOUT+/TxCLKOUT- pin. Is it allowed?

As background of this question, customer suspects taht the LVDS signal may be the source of the radiation noise.

Customer thinks that adding the damping resistance would reduce the radiation noise by making the rise and fall of the differential clock waveform of the LVDS signal gentler.

If it is allowed, what value is recommended?

I appreciate your quick reply.

Best regards,

Michi

over 7 years ago

0 Michi Yama over 7 years ago

Guru 10030 points

Hi,

I have one more question.

Can I change the drive timing of data signal for DS90C385A? If this is possible, I think this is effective for radiation noise reduction.
How do you think this idea?

Best regards,
Michi

0 Ikechukwu Anyiam over 7 years ago

TI__Mastermind 35130 points

Hi Michi,

Yes they can add damping resistors to those lines. Please see "LVDS Termination" section of this document: www.ti.com/.../snla165.pdf

For more EMI suppression techniques you can also reference this document:
www.ti.com/.../snaa205.pdf

Regards,
I.K.

0 Michi Yama over 7 years ago in reply to Ikechukwu Anyiam

Guru 10030 points

Dear I.K.-san,

Thank you for your reply.

Please answer to my other question as the below.

> Can I change the drive timing of data signal for DS90C385A?

I appreciate your quick reply again.

Best regards,
Michi

0 Michi Yama over 7 years ago in reply to Michi Yama

Guru 10030 points

Dear I.K.-san,

Thank you for your support.

I confirmed "LVDS termination" section of snla165 document.

I think this section is written regarding the termination resistor, not dumping resistor.
I would like to know the insertion of the damping resistor to each TxCLKOUT+ /TxCLKOUT- pin is allowed, or not.

Please answer me again.

Best regards,
Michi

0 Ikechukwu Anyiam over 7 years ago in reply to Michi Yama

TI__Mastermind 35130 points

Hi Michi,

15 to 30 ohms on each line is allowable if the distance is not too long. I do not think you can change the drive timing of the data signals, but you can also add damping resistors to those lines to reduce the rise/fall time for EMI.

Regards,
I.K.

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DS90C385A: DS90C385A : Insertion the damping resistor to TxCLKOUT+/TxCLKOUT