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DS90UB913Q/A comon mode choke design questions

Jack Lin
Prodigy 220 points

Hi TI Experts,

regarding common mode choke (L5) in the EVM of DS90UB913Q/DS90UB913A, because I am going to design a product which would be mass produced in several months, so I need more confident information or data about the choke.

There is a choke (L5) be designed in the EVM, is it possible for experts to help me get the answers of following questions ?

1.  Why TI design a choke for the pair of output ? and why TI short the nodes (does it mean L5 would not work on the EVM ?)

2. Did TI test and verify a working choke on EVM ? will it hurt the signal quality of output pair ? is it possible to share the result or data ?

    (as my understanding , the PCB layout of the EVM would change the trace width and might be able to hurt the impedance and the signal quality)

3. why did TI put the choke which P/N is DLW21SN216X01L on the schematic of EVM ? did it have been tested or verified ?

regards,

Jack

  • 0
    TI__Expert 5210 points
    Hello Jack,

    1. Common mode choke was used on EVM to reduce common mode noise. This is more commonly used in an Shielded twin pair ((STP) cable application. TI shorts the nodes because this is an optional component that can be used to increase signal integrity. In order to use L5 on the EVM, one must cut the traces on the EVM boards. www.we-online.com/.../blog_detail_electronics_in_action_61439.php

    2.) The choke used on the EVM was tested to work, although a formal validation was not required because this is an optional component on the EVM and not necessary for proper operation of FPD-Link. The choke will help signal integrity, not hurt it.

    3.) This is a typical component used by several of our automotive customers which is why we wanted to use it on the EVM as well.


    -Sean
  • 0 in reply to Sean Thornton1
    Prodigy 220 points

    Hi Sean,
    Thanks for your explanations and helps me to understand the choke design more.
    Please let me put a short summary as following and you can see if my understanding is correct.
    1. The reason to design a choke is "it's a very common solution of reducing common mode noise for STP application".
    2. TI already tested the choke and work on the EVM and it would not hurt the signal integrity, on the contrary it helps the signal integrity.
    3. The P/N of Murata's transformer has been designed on TI's customer side and TI put it into EVM as a reference design.
    regards,
    Jack