• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 128 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.

SN65HVD234: Ripple on the waveform

switch
Expert 2865 points
Part Number: SN65HVD234

Hi Ti Team，

With regard the output of CAN H/L for SN65HVD234DR, would you please consult TI and check if any requirement of ripple on the waveform as below picture. Thanks.

  • 0
    Guru 267550 points

    This is common-mode noise, so it will have no effect on the differential voltage. Tell the oscilloscope to subtract the two inputs.

    I suspect that this ringing is caused by the load on the power supply. Ensure that the decoupling capacitors are near the device and large enough.

  • 0 in reply to Clemens Ladisch
    TI__Guru 50555 points

    Thanks Clemens!

    Hi Switch,

    This ripple is expected for this device. The common-mode recessive bias for this device (2.3V) is different than the  dominant drive state common-mode voltage (Vcc / 2 ~= 1.85V). Because the common-mode of the bus needs to shift between these drive states, it's expected to see this shift appear. When this is applied to an actual CAN bus, the parasitic inductance and capacitance causes the energy introduced by this common-mode shift to oscillate and ring. As Clemens said, because all of this noise is in the common-mode, it does not impact the differential signal and therefore does not reduce the integrity of the CAN data. 

    Let us know if you have any more questions.

    Regards,
    Eric Schott