MCP2551 Circuit Problem in automotive

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Deion Adel
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MCP2551 Circuit Problem in automotive

Post by Deion Adel » Fri Sep 17, 2021 8:41 pm

I have an automotive problem. I installed two nodes in a industrial vehicle using MCP2515 controller and MCP2551 transceiver. I used CAN libraries for MCC18 and software is working fine.

The problem is in hardware. After the application have been working for some days, the MCP2551( MCP2551 Datasheet) is getting damaged and the problem only gets resolved if I replace it for a new one.

Does anyone have an idea of what could be happening here?
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dyarker
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Re: MCP2551 Circuit Problem in automotive

Post by dyarker » Sun Sep 19, 2021 2:41 am

The attached schematic way too small to read, and looks like only one controller with transceiver anyway.

So, do the CANH and CANL only go directly to CANH and CANL of other transceivers? (no extra grounds?)

Are CANH and CANL on twisted pairs or just a pair of individual wires?

Is a CANH and CANL pair run anywhere near the ignition system (like spark plug wires)?

Or near the heavy gauge wire to the starter motor?

Near a radio transmitter or antenna lead?

Because it sounds like transceiver ICs are being killed by voltage spikes.

Cheers,
Dale Y

dyarker
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Re: MCP2551 Circuit Problem in automotive

Post by dyarker » Sun Sep 19, 2021 2:56 am

Also, how many transceivers on the buss?

Is the buss a star or a daisy chain? A daisy chain with a termination on the ends will have less transmission line pulse collisions.

And can't see how power supply section on schematic regulates and filters the +5V.

Cheers,

(from additional reading - do you have resistors which drive recessive bus lines to 2.5V? A dominate transceiver drives CANH to near +5V, and CANL to near circuit common.)
Dale Y

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haklesup
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Re: MCP2551 Circuit Problem in automotive

Post by haklesup » Tue Sep 21, 2021 11:34 am

Need more clues about how the module failed that caused you to replace it. An easy check is to use the diode check or resistance range on a DMM and check each pin with respect to the ground and/or VDD pins to look for shorts or opens that are not on the good unit. If you find that, it indicates an Electrical Overstress condition and the pin that is effected is where you should start looking.

Your schematic does not detail how it is installed in order to estimate where the overstress may be occurring. A voltage difference on the power pin to a signal pin may be being exceeded under intermittent conditions that might be hard to catch unless you can narrow it down to an event like Starting the motor or operating an accessory.

A general approach to signal integrity in automotive can include filter capacitors added near the new module to shunt fast and medium speed transients to ground and support sags. Another approach is to isolate the data lines of the new module from the car using an opto-isolator or transformers, I'm not sure what's SOP for CAN but a search on "signal Isolation in CAN bus" popped up plenty of links to help you along.

Here is a good place to start
https://www.ti.com/lit/an/slla486a/slla ... 2220295100

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