SN65HVD230: IC failing in field - Please Review my Schematic

Anil,

Can you explain the use of R219 and R220 here? They are not needed for a typical CAN bus. Also, the VREF pin is meant to be connected to the CAN bus termination when it is in the split termination. That is, two 60 ohm resistors in series between CANH and CANL, and the VREF pin is connected at the midpoint of those two resistors. 

Also, can you give more information on the nature of the failures? If it is a CAN bus failure, populating D73 may help, but we need to understand what kind of failure signature is occurring.

Regards,

Eric Hackett

Thanks Eric for the reply. Please see below my answers to your clarifications

* R219, R220 -  330K we had  it assembled by mistake . Had planned  to use it with RS485 which had as an assembly option  using the same connector. Will remove  it for CAN.

* Vref  is floating now (R20, 68 are Not populated) .  Hope it is fine. 

* On failed devices we are seeing VCC to GND short. Other pins are OK when we check with multimeter.

Could you also please suggest  right part for D73 ?

Regards,

Anil

Anil,

Thanks for the quick reply on this.

• R219 and R220 might be the cause for failure, but I'm not sure. They are not needed for CAN though so they need to be removed.
• Vref floating is fine, the device will still work correctly.
• This kind of failure is common with a severe CAN bus failure, since the CAN bus is pulled up to VCC and pulled down to GND internally. This may have been caused by the external pull-ups, but I'm not sure that makes sense. What was happening when the failure occurred? Just CAN communication?

And another group in TI has a CAN ESD diode that will be sampling in 1Q2022. If this timeline works I can give you more details on that, otherwise the PESD1CAN is also an option, though it is a much older diode.

Regards,

Eric Hackett 

Hi Eric,

Please see my comments

* >>What was happening when the failure occurred? Just CAN communication?

Yes. Only CAN communication failure.

* Will  Remove R219, R220.

* Will use  PESD1CAN, as of now in the next revision of the board. You  may  also give me details of TI   new TVS/ESD  part that will be compatible with SN65HVD230  .  Will  give option for that  in the PCB layout.

Thanks & Regards,

Anil

Anil,

Thanks for the information, I'm still not 100% sure what caused the damage, but it may be the pull up and pull downs on the bus when the transceiver is driving a dominant pulse. If you email me directly at e-hackett@ti.com, I can give you more information on the TI part.

Regards,

Eric Hackett