FlexCase Relay Drive Stop Working

[garrettbailey]

#17348

We have the FlexCase Pro and we are using one of the high side drives (Connector 1, pin C1) to drive a relay and after driving the relay on/off after some time we are seeing the output from that high side drive stop working. We can see that the input to the high side drive to enable does toggle when we want it to but like I said the output has stopped working. Would you happen to know if there is any protection circuit built into the high side drives? Also, have you had any experience with these high side drives going out while driving inductive relays?

[Rhyse Maryniuk]

#17352

Hi garrettbailey,

Based on your message, I suspect that you are referring to our FlexCase S and the output was damaged due to overcurrent or overvoltage. The outputs on that product do not yet have protection (This feature will be available on the FCS after mid-March 2024).

If you’re driving relay coils, that should have been within specification, but its possible there was some damage somehow. For the most stability, we recommend driving outputs low side on the FCS.

The good news is that the outputs is repairable with a rework station and we can send you replacement parts. I will send you the repair guide directly.

[xuanlang]

#17377

Hi Audesse Team,

Here are more detail for this question: We were using the high side drive to enable a small automotive grade 12v relay. The noise from the relay over time seems to have damaged the high side drive. The damage caused the source to be driven from source back through the gate pin and potentially being fed back into the microcontroller. The microcontroller seems fine but we are unsure if there was any damage actually done to it. The relay did have a suppression diode, but it was clamping voltages just at or 1 to 2V above with the Mosfet/ High side drive was rated for.

can you give us some of the failure modes you have seen with these high side drives being damaged that you have experienced.

Can you also send the repair guide to my email?

Thanks,
Xuanlang

[Rhyse Maryniuk]

#17379

Hi xuanlang,

Given that implimentation, it seems strange that there were issues. The output should not have suffered an overvoltage condition. There is isolation between the gate and the microcontroller, so the micro should be fine even if the output is damaged.

Generally with the FCS we have seen that the outputs can be damaged, as there is a moderate amount of overvoltage protection (highly inductive loads could trigger damage) and no overcurrent protection built into those circuits. The circuits can unintentionally be damaged, which is why we’ve decided to add more protections into future revisions.

I’ve sent the repair guide to you for your reference.

[xuanlang]

#17383

Hi Rhyse,

How can we confirm is the MOSFET problem? From the repair guide you sent, it will require to open up the case. Are there any other reason that will cause the highside drive to stop working?

Thanks,

[Rhyse Maryniuk]

#17390

Hi xuanlang,

Damage to the individual output MOSFET is the most common cause we have seen for the behaviour you are describing. One good way to test if the hardware is damaged would be to run the same MCU code on another FlexCase S in a controlled scenario.

In this case I recommend connecting the supply voltage for the high side output to a voltage (~12V) limitted & current (~500mA) limited source, such as a power supply, for testing. One potential software bug could have been activiting both the high and low sides on the half-bridge at the same time, shorting the output due to the software configuration.

If you’ve confirmed your software is working correctly, I would be confident that the issue is hardware damage and we can organize the repair. Let me know what you find and I can assist further.

Best regards,

Rhyse

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