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ISO1050: pin 10 not connected pin 9 and pin15

Part Number: ISO1050

Hi,

1. in datasheet pin 10,9,15 are GND2.

But we measured that pin 10 are not shorted with PIN9 and PIN15. Around 20Mohm measured with multimeter.

2. My customer now has several bad devices, the bad devices are found when the CAN communication cannot be accomplished on board. The board schematic is as shown below.

We unsoldered the bad devices, finding that CANH and CANL are shorted to GND2 with <1kohm measured with multimeter. The resistance measured on good devices are around 850kohm.

Are there any risk of the schematic below?

  • Hi Howard,

    Thank you for posting to E2E! Please allow us to follow up on your first point regarding GND2 of the ISO1050.

    Regarding the devices with CANH and CANL shorts to GND2, it's possible that a transient on the bus damaged these pins. Can you share the part number for the TVS diodes, D57? For insight on this, please review our App Report on bus protection for isolated CAN systems.


    Thank you,
    Manuel Chavez

  • Manuel,

    thank you.

    Waiting for your answer on question 1. It seems that not only we have met the problem.

  • Hi Howard,

    Manuel is currently on travel and hence, I will support you in his absence.

    Regarding the question 1, could you please confirm if the samples that were tested for resistance between pin10 and pin9/pin15 were new samples or the damaged ones? Could you please also confirm if you have observed this problem on only one sample or multiple samples?

    We expect them to be short, I can quickly test a couple new samples tomorrow and confirm this to you. Thanks.

    Regards,
    Koteshwar Rao

  • The customer confirm it's on new samples.

    Since I haven't got the samples in our office, thank you for helping confirm it.

  • Hi Howard,

    I have tested ISO1050 samples for connection between pin10 and pin9/pin15, I did see similar behavior as you have mentioned. Please allow me to work with the design time to find out if this is expected and if they connect to each other after powered up. Since this is a very old device, it could take a little longer than usual to get you the answer.
    Please allow me to get back to you mid-next week. Thanks.

    Regards,
    Koteshwar Rao

  • Hi Howard,

    Thank you for your patience.
    Please note that ISO1050 has three dice inside device, digital isolator on primary, digital isolator on secondary and CAN transceiver on the secondary. Pins 9 and 15 are connected to the secondary side digital isolator GND inside device while Pin10 is connected to CAN transceiver GND. Hence, Pin10 needs to be connected to Pins 9 or 15 external for the device to work normal.

    Sorry that this is not mentioned in the datasheet, I will see if I can get this added in the datasheet. Thanks.

    Regards,
    Koteshwar Rao