• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 1888 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

SN65HVD230: Common-mode noise in CANH/CANL

Rory Wu
Intellectual 1050 points
Part Number: SN65HVD230

Hi team,

My customer used SN65HVD230, but found CANH/CANL with common-mode noise in the line. But differential value is right. Please refer to below schematic and waveform. Could you please help review an comment how to check the root cause? Thanks.

BR,

Rory

  • 0
    TI__Guru 70512 points

    Rory,

    This looks like it could be a voltage offset from the 2.2R series resistance on the CANH and CANL line. Is there any way these can be removed and then the message sent through again? Also, what are the values of R25 and R35 and are they populated?

    Regards,

  • 0 in reply to Eric Hackett
    TI__Intellectual 1050 points
    Eric,

    Thanks for the reply, I will ask customer to remove 2.2R resistors. R25 and R35 ARE not populated, is there any risk for this point? thanks.

    Rory
  • 0 in reply to Rory Wu
    TI__Guru 70512 points

    Rory,

    After reviewing this with my colleagues, the 2.2R shouldn't be an issue, but adding split termination may help. What seems to be happening here is the CANH driver is released just before the CANL driver, causing an undershoot in the common-mode voltage, and then raising back up as it decays with an RC constant back to the correct bias level. Adding split termination helps with this high-frequency undershoot by slowing it down and ultimately removing it. Split termination is shown on page 27 of the datasheet for the device. Typically the capacitor value is 4.7nF, but as high as 100nF can be used.

    Regards,