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INA210-Q1: REF pin connection

Toshiro Imi
Expert 6750 points
Part Number: INA210-Q1
Other Parts Discussed in Thread: INA210

Hello,

Our customer is asking how to connect REF pin in case INA210-Q1 is used as positive half wave current on the rails.

Do you recommend to connect REF pin to GND in this case ?

In my understanding, REF pin bias voltage depends on the current measurement range. REF pin should be connected to GND if the customer needs to measure large current accurately. He should connect to a certain voltage if he needs to measure small current accurately. Because INA210-Q1 guarantees the +/-0.02% Gain error in VSENSE=-5mV to 5mA range.

Best regards,

  • 0
    Guru 140200 points
    Hi Toshiro,

    section 8.2.1 of datasheet explains very well what to do with the REF pin.

    Kai
  • 0
    TI__Mastermind 31775 points

    Hello Toshiro,

    The customer needs to make sure that the current frequency is not too fast for the INA210. They also need to make sure the current amplitude is sufficiently high as well. I mention these two conditions because if customer connects REF pin to GND and then applies a negative shunt current, then this will generate a negative input Vsense voltage and thus saturate the INA210 OUT pin to GND. When the output of INA210 (and all other amplifiers) is saturated and slamming into the ground (0V), then the device is not technically operating in its linear region. If output is slamming into GND, but then the Vsense goes into positive cycle, there will be an overload recovery delay time in the output.

    In Figure 31, Vsense is a 2kHz signal with 20mV peak amplitude (40mV peak-to-peak) assuming the INA210 gain option of 200V/V. You can see in Figure 31, that as VOUT exits saturation, there is an intial slew boost so VOUT can catch back up with Vsense. Once this recovery is over, then device will be operating linearly and generate an accurate measurement. The blue line shows what VOUT would look like if the amplifier was ideally tracking the input.

    As the frequency increases or as the amplitude decreases, then VOUT will become more dominated by its overload recovery and customer want to avoid this.

    Hope that helps.

    Sincerely,
    Peter Iliya