DS90UB954-Q1: Differential pair Routing question

d_zero

Part Number: DS90UB954-Q1

Dear *,

please can you tell your opinion or provide a app-note that tells what is the difference between two routing cases:

Case1 : the diff signal goes from pins 24/23 on top layer and switched to layer L3 with blind via and maintains the direction

Case2: the diff signal goes from pins 21/222 on top layer and switched to layer L3 with blind via and revers ( makes a 180° turn bend?) the direction

How much more bad is the case2 to case1 in terms of signal integrity?

Best Regards,

over 6 years ago

0 Lee Sledjeski over 6 years ago

TI__Mastermind 43795 points

Hi D.

It is the same either way. Since you are going from Layer1 to Layer3, the reference plane is the same for the "red" and "green" signals so no return current vias are needed.

Regards,

Lee

0 d_zero over 6 years ago in reply to Lee Sledjeski

Genius 4915 points

Dear Lee,

thank you for the answer regarding the return current and vias.

But my question was regarding a turn bend , lets illustrate this in 3D

a) When between L1 and L3 is GND then the 180°turn in Case 2 is not a problem?

b) what if we don't have three layers, only two and Case2 then and input signal is on L1 and output signal is on L2, will then this 180°turn represent a bad angle for routing?

Best Regards,

0 Mandeep S over 6 years ago in reply to d_zero

TI__Expert 3390 points

Hi Lee,

We've done this in the past and haven't seen any issues in either case. My only recommendation would be to add a GND via next to the high speed via to help control the signal/gnd signal integrity.

Regards,
Mandeep Singh

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DS90UB954-Q1: Differential pair Routing question