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ISO1212: Design questions

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Replies: 6

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Part Number: ISO1212

Customer would like to design the ISO1212 for AC motor. There are some questions related to the ISO1212's performance and design.

1. How to calculate the power consumption of the chip?

2. How to select the C3 filter value on ISO1212EVM with consideration of the minimux turn-on duty ? 

3. What's the abxMAX current through into Pin7 of the device?

4. How much the current going though to pin 8 of the device?

5. Is Turn-ON threshold able to be adjusted to 3V, and Turn-Off be ajusted to 2V?

  • Brian,

    Power consumed the ISO1212 will depend on the current limits set by the resistors. Does the customer know the desired current limit and voltage of the system? Current going into pins 7 & 8 will again depend on the Rth and Rsense resistors being used. Table 6.9 of the datasheet has information on this with common use cases. C3 is chosen so that the low pass filter it forms with R1 does not affect the data rate being used. 3V and 2V seem very low turn-on and turn-off thresholds. The ISO121x family can only handle down to a 6.5V VIL threshold.


    Lucas Schulte

  • In reply to Lucas Schulte9:

    Hi Brian,

    Has our customer found answers to the questions you originally posted or have they been able to provide information Lucas requested? Please let us know.

    Thank you for your time,
    Manuel Chavez
  • In reply to Manuel Chavez:


    We haven't heard from you in a while. Hopefully we were able to answer your questions. Please create a new thread if you need further help.

  • In reply to Lucas Schulte9:

    Hi Lucus

    1.How to get (Calculate) power disspation results in chapter 6.5 Power Ratings ?

    2.Regarding Cin for EMC how to chose it value ? 

    3. How to get minimun turn-on and turn-of pulse duty, please use example whcin BOM can use table 3 type 1 within ISO1211 datasheet to explain it . Assume input voltage respectively 30V and 60V.



  • In reply to BOSONG JIANG:

    Hi Bosong,

    Hopefully you are well. Lucas is out of the office and will return soon. Please expect a response within the next 2 days.

    Thank you for posting on E2E,
    Manuel Chavez
  • In reply to Manuel Chavez:


    1. Please refer to this e2e post to see how to calculate power consumed by ISO121x family.

    2. Generally Cin is chosen to suppress transients that may occure in the system. It forms an RC filter with Rthr. Cin should chosen so that the RC value with affect only transients and not the systems communication signals. Also, a TVS diode can replace Cin if one cannot use a large value for Cin. Please refer to the "Typical Applications" section of the datasheet to find more information on this.

    3. I'm not sure I understand your question. The minimum pulse width for the ISO1212 is 150ns. Is this what you mean? Also see this excel worksheet for helping you design a system with the ISO1212 for specific voltage thresholds.