ISO1211EVM: ISO1211

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Replies: 31

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Part Number: ISO1211EVM

Is this evaluation Board IC capable to detect high voltage impulse  200V with short durations 1ms and convert it to 5V

31 Replies

  • Abraham,

    By "this evaluation Board IC" do you mean the ISO1211 EVM with changed and added components from the schematic you posted? Id so, then a 200V input from J2 will be reduced to 43.75V due to the 20k and 5.6 resistors. The VIH threshold will typically be 82.65V based on this configuration and will read as a logical high if there is a 200V input. This calculator document helps determine what the logic thresholds will be based on the resistor values.

    Respectfully,

    Lucas

  • In reply to Lucas Schulte9:

    TVS1,TVS2.pdfTVS1,TVS2.pdfHello Lucas

    yes, I am doing modification for the evaluation board to accept  100V ...300V at the input.

    Can this design take high pulse input and converted to 5v pulse ???

    is my design/Modification okay ???

    how about TVS 250V and 51V  ??? are they okay???

  • In reply to Abraham Choucair:

    Abraham,

    What is the system's intended input range and what are the intended logic thresholds? I need this information in order to verify that the resistor values you have chosen are correct. I would also need to know the data speed in order to determine if the value for C3 is correct. What is the application you are designing for?

    Yes the ISO121x can take in "high" input signal voltages and output 5V digital logic. One uses the equations in the datasheet or the calculator document to determine what values of resistors to use for their particular system.

    The 250V TVS diode is fine as long as you are expecting less than 250V input signals. Also the TVS diode needs to be rated for the proper amount of surge current that you may be trying to protect against. The 51V TVS diode looks ok.

    Respectfully,

    Lucas

  • In reply to Lucas Schulte9:

    Hello Lucas

    Input range 100V to 300V .. 

    Trigger from engine pulse as attached

  • In reply to Abraham Choucair:

    Abraham,

    Thank you very much for including the scope shot of the pulse. The ISO121x needs minimum pulse width of 150ns.  Is this pulse longer than 150ns? The time division is 25ms for oscilloscope so I can't tell by looking at the image.

    Respectfully,

    Lucas

  • In reply to Lucas Schulte9:

    Hello Lucas

    Yes, the pulse close to 1 ms

    so greater than 150ns

  • In reply to Abraham Choucair:

    Abraham,

    Ok. Voltages above 250V will be clamped by the TVS diode. Will the input be typically less than 250V? Is the 300V max as described before only for margin?

    Respectfully,

    Lucas

  • In reply to Lucas Schulte9:

    Hello Lucas

    Voltage max from engine trigger  300V

    as attached TVS spec breakdown 279  to 309

    is this okay ????

  • In reply to Abraham Choucair:

    Hello Lucas

    Another Question...

    can I use buffer in front of output ..????74HC7541D(schmitt trigger,buffer)U9.pdf.

  • In reply to Abraham Choucair:

    Abraham,

    Thanks for providing more information. Since your expected typical input is up to 300V, then those TVS diodes need to be removed. The 250V TVS diode clamps at 400V which wouldn't be very helpful. The 51V diode can trigger at the 300V input and shouldn't be used. Is there a particular surge rating that you are trying to achieve?

    C3 and C4 should be reduced to about 4.7nF so it doesn't filter out your 1ms pulse.

    You can use an external buffer for the ISO1211 output but these features are already built into the ISO121x devices. There is already an internal schmitt-trigger and output enable.

    Respectfully,

    Lucas