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AD4111 open wire detection

We are going to use AD4111 in our project.

We want 4 single-ended bipolar ±10 V voltage inputs, the input pins are VIN0~VIN3.

Open wire detection function is necessary.

Here are my questions

1. In datasheet, It says The VIN0 and VINCOM pins are left floating. Nothing is connected to the pins.in example 1. 

But I think VINCOM needs connected to GND, is that right?

2. When I configure the registers of VIN1I should configure CHANNEL REGISTER 1 CH1and CHANNEL REGISTER 2CH2INPUT bits to 0000110000.

Make sure the input pairVIN1, VINCOMis connected to channel 1 and channel 2. Is that right?

3. When I select the input pairVIN0, VINCOMconnected to the channel 0 and channel 15. I wonder how the chip is connected inside. Why they have two different output code? 

Do the channel 0 connect like this?

And the channel 15 connect like this

4.I also want to know the specific principle and process of open wire detection. What is COMPA pin used for

 

Thank you very much

  • Hi, 

    1. Yes, in single ended mode the VINCOM is connected to GND. 

    2.  Yes, channels must be assigned to specific channel pair. So if you want to use VIN1 and VINCOM then the channel pair required is CH1 and CH2.

    For your question 2 and 3. We do not disclose in public the internal operation of the OWD feature as it is Protected by U.S. Patent 10,852,360. But we provided in the datasheet how to detect an open wire using this built-in feature.

    So In general, in order to detect an Open wire fault the difference between the two channel conversions must be compared to a certain threshold level. And this threshold is equivalent to 300mV. If the difference of these two channel conversions is greater than the threshold voltage, an open wire fault has occurred. If the difference is less than the voltage threshold, then there is no open wire fault. And this must be support in the user software. The threshold had been determined during the evaluation/characterization of this part with the requirement of additional capacitor (680 pF) and resistor (1 kΩ) applied and connected in series between each compensation pin (COMPA, COMPB) and voltage input pin.

    Another thing to take note here is since two channel conversion is required, This effectively halves your throughput rate.

    Thanks,

    Jellenie

  • Thank you for answering my question.
    Your answer is very clear and easy to understand.
    Sorry for asking the patent-related questions.