SN65HVD1040-Q1: SN65HVD1040-Q1 permanent damage issue when CANL PIN is connected to 20V

Steven,

Your understanding is correct, the -12V to +12V recommended operating range is for functionality, and the -27V to +40V is the limitation for permanent damage. Previously, I've tested these devices in the lab to higher voltages and haven't seen a problem at +20V, so it's strange that the absolute maximum rating didn't hold up in the customer setup. 

When the voltage is applied to the CANL pin, is it connected to a power supply that is switched off, and then the power supply is switched on? Or is the power supply already on and then connect to the CANL pin? What exactly is the permanent damage being seen? And does the CANH pin have any damage during these tests? Is there a choke on the bus?

Let me know if you can answer these questions, this will help narrow down what is happening.

Regards,

Eric,
Really appreciate your response!
To answer your questions:
>When the voltage is applied to the CANL pin, is it connected to a power supply that is switched off, and then the power supply is switched on? Or is the power supply already on and then connect to the CANL pin?
Steven: The power supply is always on, and use the output line to connect to CANL pin.
>What exactly is the permanent damage being seen?
Steven: the device gave out smoke, which means it was already burn down.
>And does the CANH pin have any damage during these tests? Is there a choke on the bus?
Steven: These was unable to test as the device was burn down during the test.

In addition, during these days, my customer did more test.
During their test, they tested 12 pcs SSN65HVD1040-Q1 with exactly same test as before. Adding 24V to the CANL, this resulted out that 10 pcs were burn down. 2 pcs can survive for some time. But afterwards, those 2 pcs was also burn down if tested with long time.
So they have huge concerns on this maximum voltage that listed on the spec.

May I have your comment on this? If possible, could you share more data about the experiment you had done before? How many devices were tested? And how long?

Steven,

Thanks for all of the information. The reason I asked about the state of the power supply is because if the voltage on the CANL line is immediately stepped up to a high level with a choke on the bus, there can be higher voltage spikes associated due to the inductance. I wouldn't expect this to be the case with multiple devices, but it would still be good to know if there is a choke on the CAN bus though.

In my experience, even with testing for absolute maximum ratings, there usually isn't smoke associated with the fail. I usually see smoke when there is a short to GND or some kind of short that causes a large, constant current draw from whatever supply is being used to the apply the energy. 

As for the testing, prior to these devices being released, they are run through an automated test program, along with bench testing, to verify these datasheet specifications. I'm not sure how long the voltage is applied in the automated test program, but in the bench testing, the voltage is applied for a few seconds, and then functionality of the device is tested. 

When this is being tested, is it on the application board? Is there any way a schematic and/or layout can be shared? 

Regards,

Hi Steven,

If problems like this persist, I would recommend moving from SN65HVD1040-Q1 to either SN65HVD1040A-Q1 or SN65HVDA1040A-Q1 (both of which are the same device). These updated versions have some improvements made with respect to transient overvoltage tolerance, and this is useful for short-to-battery testing since the CAN bus voltages can overshoot far beyond the battery voltage levels during the test as the short connects/disconnects or as the transceivers toggle between dominant and recessive states. You may also want to consider our newest TCAN1042-Q1 device, which is a p2p update to SN65HVD1040.

Regards,
Max