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ISOM8110: ESD Protection on the inputs for 24V system

Neet
Intellectual 612 points
Part Number: ISOM8110
Other Parts Discussed in Thread: ISO1212, ISO1228, TSM24A, ISOM8610, ISOM8600

Tool/software:

Hello TI E2E Community,

We are planning to use the ISOM8110 series Opto-emulators for our Digital Input use case and want to understand the need for ESD protection on the filed side input of the device.

We anticipate few ESD events, but frequent EFT events at the field input side.

Also, suggest any reference design optimized for minimal power consumption that we can use on the input side of the digital input module for industrial use case.

  • 0
    TI__Mastermind 31825 points

    Hello Neet, 

    Thank you for reaching out, 6.2 ESD Ratings lists the ESD tolerance of the ISOM8110. The EFT standard is a different series of tests (IEC 61000-4-4) and the ISOM8110 may need additional protection diodes to pass. The following reference designs and app notes provide a good reference on methods of passings IEC 61000 tests. 

    1. Surge, EFT, and ESD Protection Reference Design for PLC Analog Inputs (Rev. A)
    2. IEC 61000 ESD, EFT, and Surge Bus Protection for CAN Reference Design (Rev. B)
    3. Simplifying EFT, Surge and Power-Fail Protection Circuits in PLC Systems (Rev. D)

    I would also like to mention that one of our isolated digital input solutions may help you to meet your application requirements for both low-current consumption and surge protections. ISO1212 and ISO1228 offer an integrated current limit and easy implementation of surge protections. Below is a quick comparison side of isolated digital input solutions. 

    ISOM8110 is recommended for the traditional resistor ladder and discrete current limit solutions. 

    Best,
    Andrew

  • 0 in reply to Andrew J
    Intellectual 612 points

    Hello Andrew,

    Thank you for the details. Can you help me understand the following specifications as given on the datasheet of the ISOM811x?

    I want to use ISOM8110 for our Digital Output use case where we send a pulse signal to the PLC situated remotely about 100m away via 24V signal line.

    Kindly let us know if this ISOM8110 can be used in this use case - we plan to use TSM24A for output protection. Let me know if we would need any additional protection in this use case.

  • 0 in reply to Neet
    TI__Mastermind 31825 points

    Hello Neet, 

    I happy to help. The datasheet line "surge capability: up to 10kV" is refereeing to VISOM in table 6.4 Insulation Specifications. This spec demonstrates the ISOM8110's isolation capability and that it can withstand a transient from side 1 to side 2 per IEC 62368-1. We refer to this an "across the isolation barrier surge". 

    ESD, EFT, and Surge according to the IEC 6100-4-x standards refers to same side strikes, or transients to individual datelines or pins. ISOM8110 is only tested to the levels in 6.2 ESD Ratings which are not part of IEC 6100-4-x.

    Neet said:
    I want to use ISOM8110 for our Digital Output use case where we send a pulse signal to the PLC situated remotely about 100m away via 24V signal line.

    I would expect ISOM8110 to work here. Please also see the ISOM8610 and the ISOM8600 which have a higher current rating which may be useful over the long distance.

    Also, I expect TSM24A to be enough protection, however, please make a new thread with "TSM24A" in the title and a Protection Devices focused team help if you have more detailed questions.

    Best,
    Andrew