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INA226-Q1: INA226-Q1 reverse current protection question.

user6074725
Prodigy 30 points
Part Number: INA226-Q1
Other Parts Discussed in Thread: INA226,

Dear Sirs,

 This is Quanta PEE in taiwan than Ask the following questions.

1. 

We should use shun model. There are 16bits in total, we can set it through I2C.

1bit=+-2.5uV, 16bits=81.9mV. This represents the cross-voltage that can be detected = +-2.5uV to +-81.9mV.

Is my understanding correct?

2.

What is the default value of reverse current (cross voltage)? ?mV, ?bits.

3.

Does the voltage detect to protect the reverse current through I2C? Can we set bits through our MCU? or it need Burning tool? 

Thank you very much

  • 0
    TI__Mastermind 26750 points

    Hello user6074725,

    Welcome to the forum and thank you for your questions.

    Let me make some definitions before answering your questions.

    • Vin = Vshunt = input differential shunt voltage = (V_IN+) – (V_IN-)
    • Vshunt = Load_current * Rshunt
    • FSR = full-scale range. Measurable input voltage range for the ADC.
    1. Since the internal ADC of the INA226 is 16-bit and the FSR is +/- 81.92 mV, the least significant bit (LSB) size is 2.5 uV for the input shunt voltage measurement. All of these values are listed in the Electrical Characteristics table in section 6.5.
    2. If the load current is flowing in negative direction (Vshunt < 0 V), then INA226 will report as a negative Vshunt or negative load current measurement. The INA226 can measure negative Vshunt all the way to -81.92 mV.
    3. The INA226-Q1 communication bus (SDA and SCL) is I2C compatible with any MCU/processor I2C bus. Thus, registers can be read and/or write through this bus. Since these bus lines (SDA and SCL) are usually pulled up to the VS voltage rail (see datasheet cover page) and are open drain input/output (see section 5 of datasheet), there should be no need to protect from a “reverse current through I2C”. The communications bus of the INA226 is completely independent of the shunt and bus voltage measurements at IN+, IN-, and VBUS pins of device.

     

    Hope this helps. Please post back if I have not answered your questions.

    Sincerely,

    Peter