TS3DV642: Differential impedance measurement by TDR for TS3DV642.

yoshiki hasebe

Part Number: TS3DV642

My customer asked us about differential impedance measurement by TDR for TS3DV642.
As you can see, it is stable at around 104 Ω without TS3DV642, but it is around 117 Ω with TS3DV642.

Figure1.:Without TS3DV642

Figure2: With TS3DV642

There is a difference with or without TS3DV642.

Is this an effect of ON resistance?
The difference between presence and absence of TS3DV642 is 13 Ω.
He is concerned that since the ON resistance of the TS3DV642 is TYP 6.5 Ω, since it matches when doubling it at the signal sink and source, the ON resistance is raised as it is.

Please let me know the above question.
Also please let me know the solution to this symptom.

Best Regards,

Y.Hasebe

over 5 years ago

0 JMMN over 5 years ago

TI__Guru 60865 points

Hello Hasebe-san,

Yes, this impedance change is caused by Ron of the TS3DV642.

Regards,
JMMN

0 yoshiki hasebe over 5 years ago in reply to JMMN

Mastermind 6385 points

Hello JMMN-san,

Thank you for your reply.

My customer want to reduce the increased impedance.

Please let me know how to reduce the impedance.

Best Regards,

Y.Hasebe

0 JMMN over 5 years ago in reply to yoshiki hasebe

TI__Guru 60865 points

Hello Hasebe-san,

There is no way to modify the Ron impedance, but the customer can adjust the PCB impedance which may provide more margin.

Regards,
JMMN

0 yoshiki hasebe over 5 years ago in reply to JMMN

Mastermind 6385 points

Hello JMMN-san,

Thank you for your reply.
I explained your comment to my customer.
He asked us about as additional below questions.
Please let me know additional below questions.

1.On the principle that ON resistance influences:
　I understood that the cause is in ON resistance.
　However, I do not know why the ON resistance is added by TDR measurement.
　So, please let me know the principle of adding ON resistance.

2.On the case of reviewing PCB impedance after HDMI-SW (TS 3 DV 642):
　Please let me know the specific case of actually taking such measures on the matter of adjusting PCB impedance after HDMI-SW (TS3DV642).

Best Regards,
Y.Hasebe

0 yoshiki hasebe over 5 years ago in reply to yoshiki hasebe

Mastermind 6385 points

Hello JMMN-san,

Could you please help us about yesterday's above questions.

Best Regards,

Y.Hasebe

0 Nicole Han over 5 years ago in reply to JMMN

TI__Intellectual 2230 points

Hi, JMMN,

My customer has the same problem, how can they adjust the pcb layout. Thanks!

0 David (ASIC) Liu over 5 years ago in reply to Nicole Han

TI__Guru*** 139405 points

What is their current PCB impedance? Can they lower it to 95ohm? If they have s-parameter of the board, can they share with us so we can simulate it first?

Thanks
David

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TS3DV642: Differential impedance measurement by TDR for TS3DV642.