SN65HVD255: Ripple of CANH/L

Lilian,

Ripple is not ideal in any communication interface, however, in this instance, it looks to be okay. The issue that could be caused with this is a delay in meeting the receiver threshold of 900mV. The Vid (VcanH - VcanL) for this device (as with all CAN devices) is 900mV when transitioning from recessive to dominant, meaning that for the receiver to correctly interpret the bit, the differential voltage between CANH and CANL needs to meet the threshold of 900mV.

Because there is an immediate spike up to 3V on the CANH-CANL waveform in your screenshot, this shows that the receiver interprets the bit correctly in time, and won't cause any delay in the receiver, thus communication will work normally. The other parameter to look for is the dip after the initial spike; when transitioning from dominant to recessive, the threshold is 500mV. If the successive dip after the initial spike dipped below 500mV, this would cause the receiver to respond incorrectly and show a recessive bit on the receiver. In this application, that isn't the case, as the dip goes to ~1V before it recovers back to the dominant state.

There shouldn't be any issue created with this ripple.

Regards,