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ISO1540: I keep Blowing up my isolator when plugging and unplugging my battery

Jose Luis Espinosa Mendoza
Prodigy 10 points
Part Number: ISO1540

I am using a ISO1540 to read the SMBus of some BB2590 batteries. The relevant part of the circuit is shown in the images below

The issue that I am having is that sometimes when connecting or disconnecting the batteries, U14 gets damaged (no signs of damage, no short circuit or anything visible) and I stop getting telemetry of the Cell 1 of the battery until the IC is replaced with a new one.

The connector of the battery is rigid and that allows all the cells to connect 'at the same time'.

I suspect that the issue might be related to the fact that U14's Ground is the Positive side of Cell 0 of the battery and maybe during the connection/disconnection process there is a voltage spike or similar, but not 100% sure.

Anyone has any pointers on how I could protect the ISO1540 to avoid damaging it with the normal use of the battery?.

J10 is a JST, J5 and J6 is an XT30, they are wired to a connector similar to this one: tacticaleng.com/bb-2590-smbus-male-connector

With a PCB ike this one: tacticaleng.com/pcb-2590

So when the battery is plugged in, it is plugged in to the connector in the links. J5, J6 and J10 are "hard wired" to the PCB

  • 0
    TI__Expert 8030 points

    Hi Jose,

    Thanks for reaching out.

    We are currently looking into this, and will get back to you within the next 24 hours.

    Regards,

    Kenneth

  • 0 in reply to Kenneth Arnold
    TI__Expert 8030 points

    Hi Jose,

    Thank you for your patience.

    The schematic looks good. I'm not seeing any issues with how you have the device connected in your design. Therefore, to gain a better understanding for what may be causing this issue, I have the following questions:

    -When you connect the battery to the PCB, are the data and power line connections between the battery and PCB connected at the same time? Or are they connected at different points in time? If they are connected at different points in time, in what order are they connected?

    -If possible, can you also please provide an oscilloscope screenshot that shows the behavior of the data and power lines at the instant they are connected to the battery?

    -When U14 fails, what is the failure signature of the device? Do the SCL1 and SDA1 waveforms no longer match the SCL2 and SDA2 waveforms whenever power is being applied to VCC1 and VCC2? Or does the device have a different failure signature? Could you please provide another oscilloscope screenshot that clearly shows how U14 is failing? If possible, please include the following signals in the oscilloscope screenshot: SCL1, SDA1, SCL2, SDA2, VCC1, VCC2.

    -Have you tested a failing U14 device on a different board, to see if the device still fails when it is used with a different PCB/design? If not, could you please test a failing U14 device on a different PCB to see if you are still able to transmit data from SCL1 and SDA1 to SCL2 and SDA2 (for testing, you could use the evaluation module for this device, which I have linked here: https://www.ti.com/tool/ISO154XEVM)?

    -How many ISO1540 devices have you tested? From the total amount of ISO1540 devices that you have tested, how many are showing this behavior?

    -Once you see a failure in an ISO1540 device, does it ever work again?

              -How many total times do you have to disconnect and reconnect the battery from the PCB in order to get the ISO1540 to fail?

              -Once U14 fails and is replaced with a new ISO1540 device, does the new device fail again after a certain number of disconnect and reconnect events with the battery? Or does it continue to work forever without failing?

              -Is U14 the only component that always fails when the battery is disconnected and reconnected?

    Regards,

    Kenneth