• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 34 subscribers
  • Views 824 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.

SN65HVD235: DC/DC switching regulator as power supply

Massimiliano De Cristofaro
Expert 6640 points
Part Number: SN65HVD235
Other Parts Discussed in Thread: TPS763, LM5165

Hi team,

one of my customers would like to use a DC/DC switching regulator as power supply for the SN65HVD235. 

In the datasheet a LDO (TPS763) is recommended but:

- Is the transceiver very sensitive to the noise coming from DC/DC regulator? 

- is it possible to optimize the DC/DC switching regulator and use it?

- if yes, what do you suggest? is the LM5165 suitable for this application?

Thanks a lot in advance for your help.

Best regards,
Massimiliano De Cristofaro
Texas Instruments FAE

  • 0
    TI__Guru 74282 points

    Massimiliano,

    In general, any communication interface is going to be susceptible to noise coming from a switch-mode power supply. With proper layout and filter techniques, and component selection, these can be greatly mitigated to not disturb the CAN communication. So to answer your questions:

    • Not any more sensitive than another CAN transceiver, but yes in general the noise emitted from switch-mode power supply's switching currents can and will affect the communication bus if not dealt with properly.
    • Yes, this is possible.
    • That power supply will work, and with low current output and low quiescent current, the noise emitted will be fairly low relative to a power supply with a higher load. The switching frequency might be a problem depending on the data rate of the application. To recommend a device I'll need a little bit more information about the application.

    • What data rates will this application be working?
    • What kind of voltage do you need outputting from the buck? I'm assuming 3.3V, but just want to check.
    • Will the buck converter be converting the car battery voltage? Or some other voltage?
    • Is there a specific reason the SN65HVD235 was chosen?

    Regards,

  • 0 in reply to Eric Hackett
    TI__Expert 6640 points
    Hi Eric,

    thanks a lot for your support!

    Please find below the answers:

    The DC/DC was an XP-power ISE0503A-H, is an isolated DC/DC Converter with input at 5v and output at 3,3V. This converter is powering only the CAN transceiver and 4 schmitt-trigger and 2 optocouplers for the TX and RX lines that arrive to the transceiver.

    The speed of CAN is 250Kbits/s

    The reason of selecting the HVD235 is because it is the recommend transceiver in the 28335 DSP datasheet.

    - What do you recommend in this case?

    Thanks again.

    Best regards,
    Massimiliano.
  • 0 in reply to Massimiliano De Cristofaro
    TI__Guru 74282 points

    Massimiliano,

    Thanks for all the info. The buck converter you've chosen will work fine, I would just recommend not using switching frequencies that are multiples of 125kHz (250kHz, 500kHz). In your spectrum, the noise at these peaks will already be accentuated by the CAN data on the bus, and will only be added to by the switch-mode power supply.

    The SN65HVD235 is a fine choice, but will the customer be using the AB or RS pins? I only ask because we have newer devices available that work with 3.3V IO levels.

    Regards,

  • 0 in reply to Eric Hackett
    TI__Expert 6640 points
    Hi Eric,

    thanks for your answer.
    I have sent it to the customer.
    I will come back to you in case of any feedback.

    Thanks again!

    Best regards,
    Massimiliano.