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Original question:

ISOM8111-Q1: Application inquiry

ISOM8111-Q1: Evaluation method for ensuring reliability of photocoupler operation and durability

HyunGun Choi
Prodigy 80 points

Part Number: ISOM8111-Q1
Other Parts Discussed in Thread: ISOM8111, ISOM8110

Tool/software: 

Please refer to the circuit currently in use below.

To ensure the reliability of the photocoupler's operation and durability, please identify the items you deem necessary for verification and reply.

(Please provide specific details regarding the items required for verification, evaluation methods, etc.)

* The Vin voltage in the circuit below is supplied by an external switch input.

* If you need additional information to verify your request, please let me know.


  • 0
    TI__Mastermind 34580 points

    Hello Hyun, 

    Thank you for reaching out. The topology of both schematics looks good. For verification I would suggest designing for the following parameters:

    1. VF - To make sure the diode is on make sure the VF(max) is surpassed to properly bias the diode emulation
    2. IF - Similarly to #1 please make sure the IF(min) is set above 700uA, most industry applications use an IF of >1mA for margin. 
    3. IC - Design the ISOM8111 to be in saturation mode for best switching performance since the opto-emulator will be acting as a switch to drive the transistor. 
      1. Saturation mode is when IC_max << CTR *IF. Where IC_max is the current limit set by the R106 pull up resistor.  

    Follow-up with more questions as needed. 

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 80 points

    Currently, there are no test evaluation criteria for this circuit.

    I'd like to inquire about any recommended evaluation methods to establish evaluation criteria.

    Ex1) To check the durability of the photocoupler, how many times should the input switch ON/OFF operation be repeated?

    Ex2) To check the durability of the photocoupler, under what temperature conditions should the switch ON/OFF operation be tested, etc.

  • 0 in reply to HyunGun Choi
    TI__Mastermind 34580 points

    Hello Hyun, 

    In short, TI guarantees datasheet performance as long as the absolute maximum conditions are not exceeded, and the device is considered ready upon arrival/when mounted to the PCB. You are welcome to do additional quality checks on your system. 

    The device is rated for operation from -55V to 125C. Therefore, select a temperature that best meets your application requirements. The device also does not need to be switched to prove reliability since this is covered by TI's testing. You can use a 1kHz signal to validate operation if needed.

    TI does numerous quality checks to ensure the reliability of our devices. Also, keep in mind that ISOM8110 is an opto-emulator. This means that the there is no photodiode, rather the same behavior is replicated (emulated) to match traditional photocouplers using TI's reliable digital isolation technology. The device will not degrade over lifetime due to LED-aging. (+) [FAQ] What are the benefits of Opto-emulators vs. Optocouplers?

    Best,
    Andrew