TLK1501 Serdes EVM Kit pcb layout.

Sergey Avdjushin

Other Parts Discussed in Thread: TLK1501

Hello!
I'm going to use the EVM Kit as a prototype for the project.
http://www.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=sllu008
Please help to understand next things.
1)I realized that under the Thermal pad circuit is one large hole and several small holes. Is it correct? (Figure A–3.Top Layer 1)
2) TLK1501 has a high-speed serial differential bus. But in the EVM kit they are made as two 50-ohm lines.
I am going to connect the TLK1501 to SFP laser module which has a differential input and output.
Will it be better if I connect it with differentials 100 ohm line? Something like 5mil line and clearance, as we route Ethernet on PCB?

Serg.

over 12 years ago

0 Michael Peffers over 12 years ago

TI__Mastermind 20820 points

Hi Serg,

You are correct, there are vias placed under the TLK1501 to enhance the thermal characteristics of the device.

The termination scheme that you use will be depicted by the optical module that you re using. If the Tx and Rx are differential lines with 100ohm termination then you should follow that scheme. This information should be available in the data sheet provided by your optical module vendor.

Regards,

Mike

0 Sergey Avdjushin over 12 years ago in reply to Michael Peffers

Intellectual 285 points

Thanks for the reply!

About the vias.
If I read the datasheet, I can see there are vias placed under the TLK1501 to enhance the thermal characteristics of the device.
That is clear.
But in the next document on the PCB layout I see something big and round under the TLK1501.
http://www.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=sllu008
Pages A5 - A20.
What is this? Is this one big VIA or something else?

Serg

0 Michael Peffers over 12 years ago in reply to Sergey Avdjushin

TI__Mastermind 20820 points

Hi Serg,

This is a large via connecting the power pad to the group plane for heat transfers away from the IC.

Regards,

Mike

0 Sergey Avdjushin over 12 years ago in reply to Michael Peffers

Intellectual 285 points

Thanks a lot!
In addition, I thought that a large hole under the chip enables the soldering iron to solder through the hole. Soldering station is not needed.
Serge.

0 Michael Peffers over 12 years ago in reply to Sergey Avdjushin

TI__Mastermind 20820 points

Hi Serge,

You are correct, the large hole in the PCB is there to allow for a soldering iron to be used when soldering the IC down. This eliminates the need for a special soldering process.

Regards,

Mike

0 Sergey Avdjushin over 12 years ago in reply to Michael Peffers

Intellectual 285 points

Thanks!

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TLK1501 Serdes EVM Kit pcb layout.