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ISO1211: Problem with the comum ground

Prodigy 10 points

Replies: 1

Views: 89

Part Number: ISO1211

Hello Team!

I'm developing a board, then I need to "convert" 24V input to 3.3V output. But, I saw in the datasheet the common ground, but when I was testing this didnt work, so I tested connect the FGROUND to the ground of 24V and 3.3V to GROUND.

Im testing this with two power supplies, do I really have to separate the grounds?

My english is a little bit rusty, so I appreciate your help!

  • Hi Thiago,

    Welcome to TI E2E Forum!

    Thank you for showing interest in ISO1211. The device ISO1211 is an isolator that isolates 24V to 60V field digital inputs and provides the isolated output to an MCU at a more suitable voltage levels. The device is an ideal fit for applications that require isolation but of course the device can be used in other ways if it serves the purpose.

    From your post, I understand that you are trying to convert 24V input to 3.3V output to interface it to an MCU. ISO1211 can certainly accept the 24V signal input on the field side (IN / FGND) without needing a separate power supply on the field side. Since MCU side (VCC1 / GND1) is isolated from field side, the MCU side will need an isolated power supply if the isolation is desired between field input and the MCU, as shown in the below application diagram. If the isolation is not desired then you can certainly short FGND & GND1 and power VCC1 with 3.3V rail which is powering the MCU.

    Is your 24V input a field input that is compliant to IEC 61131-2? For more details related to digital input module in PLC applications, please refer to the below link to an application section on TI website. Let us know if you have any other questions, thank you.

    Koteshwar Rao