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INA302: Design guidelines for the monitoring AC Voltage and Current

Part Number: INA302
Other Parts Discussed in Thread: OPA333, INA226

As per this design Guidelines

* It says input of max of 400V (Is that referring to DC /AC)?

* I did not understand use of Rz with Zener Diode since Zener Diode will have Dynamic resistance internally.

* As I can see from the design Opamp is supplied with 5.1V using Zener Diode. If in case of input > 100V Wont it damage the Zener and also Opamp?

Can I do this :

AC Voltage to the ADC pin by dividing the AC Voltage to max voltage level of ADC pin of the controller followed by Diode to the ADC pin?

Any suggested guidelines for AC Voltage measurement?

Thanks.

  • Hi Lakshminarayana,

    it's DC. Across the zener diode a voltage of 5.1V is dropping with the programmed current then. Equation (1) can be used for better understanding.

    Kai

  • Hi kai,

    Thanks for your reply.

    Any idea on AC Measurement?

    Thanks.

  • Hello Lakshminarayan,

    Thanks for considering to use Texas Instruments.  The zener diode keeps the voltage potential between the OPA333 supply and ground pin around 5.1V, which ensures that absolute max condition for the device supply pin is not violated.  The Rz resistor provide a current path so that a potential between the anode and cathode of the diode can reach the reverse breakdown threshold and power on the device.

    I cannot provide a reference design for measuring high-side AC measurements.  However, I think you might be able to modify the reference design you were looking at such that there are two opa333s, two fets, and two optocouplers to create a bidirectional sensing circuit.  The idea would be that the load nodes are reversed on the second opa333.  Thereby as the current reverses, one PFET would shut off while another should turn on.  Between the drain of each PFET and the sense resistor connected to the INA226 would be an optocoupler.  When current passed through an optocoupler, a gpio could be toggled high or low to indicate which FET was turned on thereby indicating the direction.

  • Hello Lakshminarayan,

    I have not heard from you in a while.  As such I presume you have a better understanding of the reference design circuit and have a possible idea to explore for your AC measurement.  Therefore I am going to close this thread.  However, if you do need further support, please reply below to reopen the thread.