• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 82 subscribers
  • Views 251 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F280049-Q1: Impedance matching control from ePWM to mosfet Driver input

RookieP Soybean
Prodigy 70 points

Part Number: TMS320F280049-Q1
Other Parts Discussed in Thread: TMS320F280049, UCC21330

Hallo,

I am working on a CLLC power supply. As per PCB layout design, I have 2 pair of ePWMs routing from tms320f280049 to mosfet driver. Total length of routing for each ePWM is around 10cm long.

Should I tell PCB layout engineer or PCB manufacturer to carefully control impedance matching issue of these ePWM?

How to define the impedance parameter, 50ohm? 90ohm?

 

Thanks.

 

 

  • 0
    TI__Mastermind 23611 points

    Hi,

    Impedance matching is typically reserved for systems where differences in trace impedance can cause issues. For example, typically analog signals which leverage differential 16-bit ADC leverage impedance matching to make the most out of the higher resolution ADC sampling. Another example could be for communication, for example the FSI signals which operate at high frequencies benefit greatly from having impedance matching.

    What are the switching frequencies for the PWM signals? I have not seen PWM signals at 10kHz to 200kHz utilize impedance matching as the potential benefits are minimal and the increase board production cost is not worth it. If you are operating the PWMs in the MHz range and doing things like leverage HRPWM, then you may choose to consider this

    Regards,

    Peter

  • 0 in reply to Peter Luong
    Prodigy 70 points

    Hallo, Peter:

    The variable frequency of my CLLC power converter is 70~250kHz.

    The hardware design for mosfet gate-source routing is F280049 --> ePWM routing --> UCC21330 driver --> Mosfet gs. I can understand the routing from UCC21330 to Mosfet gs doesn't need to control impedance, but how is the routing from F280049 to UCC21330, are there any consideration for this routing?

  • 0 in reply to RookieP Soybean
    TI__Mastermind 23611 points

    Hi, 

    Are there any other signals that have impedance matching on the board? If so, then there wouldn't be additional cost for impedance matching PWM signals. I think 50 ohm is typical. But otherwise, I don't believe there would be a large impact on the signals, since you would also have a deadband configuration on the PWM signals. 

    Regards,

    Peter