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ISO1540: Output failure problem

Rhea Gao
Expert 2350 points
Part Number: ISO1540

Hi，

The chip is used as I2C isolation, with MCU 3.3V IO on the input side and CH452 5V on the output side. According to the recommended schematic design, the signal on both sides has 2.2K pull-up, and the power supply is decoupled by 0.1uF.

The specific phenomenon is that after the chip continues to work for a period of time (2-8 days), the high level of SDA and SCL on the output side drops to 2V or 0V, and internal damage is suspected. The fault reoccurs some time after the device is replaced.

The output side is an independent circuit board, the test cable is larger than 6 meters, and the communication rate is 100K.

Please help to check what is the problem? Many thanks~

  • 0
    TI__Expert 8030 points

    Hi Rhea,

    Thanks for reaching out. The behavior that you have observed with this device is not expected. From what you have described, it is possible that there is something in your application that is violating the datasheet specifications of this device. Here are some questions that I have about your application:

    Of all the devices that you have tested, how many are behaving as you have described?

    Have you performed any additional tests, such as EMC or overvoltage?

    Could you please provide a schematic of your application, so that I can see how you have connected the ISO1540?

    Regards,

    Kenneth

  • 0 in reply to Kenneth Arnold
    Expert 2350 points

    Hi Kenneth,

    As shown in the following figure,      MCU-> Isolation -> Socket

  • 0 in reply to Rhea Gao
    TI__Expert 8030 points

     Hi Rhea,

    Thanks for sharing the schematic. Everything in the schematic that you have shared looks good, could you please share the part number of the MCU and a schematic that shows how you have the MCU connected to the device?

    Additionally, here are some questions that I have about your design:

    1. Could you please share both the input and output waveforms of the the ISO1540 that show the output in error?

    2. How many devices were tested, and how many devices failed in the way that you have described?

    3. When you observed the failure that you described, were you performing any EMC or additional tests?

    Regards,

    Kenneth

  • 0 in reply to Kenneth Arnold
    TI__Expert 8030 points

    Hi Rhea,

    Since I have not received a response from you, I am assuming that you have resolved this issue. Therefore, I will close the thread. If you have not resolved this issue, please share the information that I requested in the previous response.

    Regards,

    Kenneth