TCAN1051HV-Q1: TCAN1051HV-Q1

We have seen Both CAN FUSE open and ESD diode failure in field . In all cases this failure happened only during Charger Grid disconnection or making&Breaking. 

Hi Rami,

I've removed the attachment in your previous post as it was marked "Confidential" and this is a public forum. I can still reference it internally and provide feedback accordingly.

It sounds like the Fuses and TVS diodes are responding to transience caused by connecting or disconnecting the charger grid to the system. This would likely occur if there is a significant voltage difference between the board supply and the charger supply. It could also be influence by inductive kick-back from the switch in current directions.

1. Does TCAN1051HV-Q1 display an signs of damage after this failure? Does it draw excessive current/heat up significantly? Is communication still possible through the effected node?

2. I see in the diagram that the connecting charger grid has CAN lines. Are these lines being connected to the effected node's CAN lines? I believe this is the CANOE node in the diagram.

3. Page 2 diagram shows a common ground between battery and charger. Page 3 describes isolated grounds. Could you specify the grounding of the effected node and the order in which the connection is made? (BAT- then PACK+ then CANH/L for example)

Regards,
Eric

1. Does TCAN1051HV-Q1 display an signs of damage after this failure? Does it draw excessive current/heat up significantly? Is communication still possible through the effected node?

Ans : No. TCAN was perfectly working fine. In only 1out of 12 failure cases TCAN : CANH to Ground impedance was less i.e 100k. But it was working fine. Checked bit timing also.

2. I see in the diagram that the connecting charger grid has CAN lines. Are these lines being connected to the effected node's CAN lines? I believe this is the CANOE node in the diagram.

Ans : Charger CAN lines are not connected to effected CAN line (Battery)

My entire Swapping Station has 15 charger Slots. Each row 5 has Batteries.. All Charger(15 chargers total) CAN line connected to CANOE. PC controls the chargers Via CAN to Ethernet communication.

There are 2 CANOE s. Each CANOE has 2 channels. Each row ( 5 batteries) connected to one CANOE channel. So 3 channels for batteries and one channel for Chargers. All are in control communication with PC.

3. Page 2 diagram shows a common ground between battery and charger. Page 3 describes isolated grounds. Could you specify the grounding of the effected node and the order in which the connection is made? (BAT- then PACK+ then CANH/L for example)

Ans: Each Charger Slot has connection to Battery with Common Ground. Battery Ground and Battery CAN are running on the same Ground. But Charger CAN isn't connected to Battery CAN. and also Charger CAN is isolated to its Ground.

Failures are very rare and not repeatable.

That's why i couldn't able to troubleshoot with CRO also. Please guide me how to proceed further to identify the root cause. Once root cause is identified then solution can be given very fast. I know isolated CAN will solve the problem. But We have already 1000 batteries in field. I have to give immediate corrective solution also as business model

Hi Rami,

Thanks for the information. This seems like a difficult problem to pinpoint. It appears the fuses current rating is higher than TCAN1051's short circuit current meaning a DC fault is unlikely. Because TCAN1051 does not appear damaged and the TVS shows evidence of a breakdown voltage, there is likely a large pulse being discharged through the CAN lines for some reason. I understand that this happens when the system is connected to the charger and does not occur otherwise. This leads me to believe some transient is created during the connection. 

4. Could you describe the failure in more detail? Are both the Fuse and TVS damaged? Does the choke appear damaged? Is system communication possible after failure?

5. When the Fuse fails, do both CANH and CANL Fuses fail? One or the other?

6. Is there a correlation between failing nodes and which CANOE they are connected to? CANOE - BATT - BATT fail or CANOE - BATT - CHARGER fail?

7. Would it be possible to share a more complete schematic of the system? If so, I can reach out to the email you have registered with E2E to share potentially confidential information offline. 

Regards,
Eric

4. Could you describe the failure in more detail? Are both the Fuse and TVS damaged? Does the choke appear damaged? Is system communication possible after failure?

Ans: Total 8 Failures Studied.

2 Failures : ESD Short+2CAN FUSE open

1 Failure : ESD open + 2 CAN fuse open

2 Failure : ESD ok+ Only CAN H Fuse open

3 Failure : ESD ok + 2 CAN Fuse open

Communication not possible as fuse is opened

CMC appear ok in all cases

System level also nothing else found to be faulty.

5. When the Fuse fails, do both CANH and CANL Fuses fail? One or the other?

Ans : pls refer above ans

6. Is there a correlation between failing nodes and which CANOE they are connected to? CANOE - BATT - BATT fail or CANOE - BATT - CHARGER fail?

Ans : Failure observed in all 3 CAN Nodes.

7. Would it be possible to share a more complete schematic of the system? If so, I can reach out to the email you have registered with E2E to share potentially confidential information offline.

Ans : I will share you once i reach office as i dont have system level diagram with me

i captured this today during chargers Turn ON. i could see 125 transients on CAN lines which may be the failure mode but during this also There was no failure observed. but transients are there on every charger AC voltage turn ON.

can you pls comment on this

Hi Rami,

This transient pulse looks significant enough to stress the fuses and TVS's in the system. It appear that the TVS diode is unable to clamp this transient to its specified value (~40V). The resulting voltage across the fuse may spike above 125V periodically and may - over time and enough exposures - see failure. 

I will wait for a diagram or schematic before commenting on possible solutions or other probable causes. I have been copied on the parallel email chain. Please find my information there to share information offline.

Regards,
Eric