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INA226-Q1: How to select the shunt resistor

Part Number: INA226-Q1
Other Parts Discussed in Thread: INA226

Hi sir,

I created the INA226 schematic by figure.21 in the datasheet and I used R filter=10 ohm, C filter=0.1uF.

If the Vbus=0.75V and current is 1A, the R shunt is 0.005 ohm and then the V shunt value is 5 mV ?

Is it right ?

How can I find the register value to verify the V shunt value ?

If the current is 500mA, then I need to adjust the R shunt value to 0.01 ohm to get the V shunt value is 5 mV?

  • Hello Kevin,

    Thank you for using the TI forum.  Yes, your math is correct for the expected shunt voltage (and both situations you mentioned would have an expected shunt voltage of 5 mV). To convert the register value to V, you just multiply the value by the LSB (2.5 µV).  If you are curious about the what the expected register value would be for your specific case, you can just divide by the LSB instead. So, at 5mV, the register value should be 5m / 2.5µ = 2000 (or 0x7D0).

    If you have having a hard time deciding what shunt value to use, I recommend looking at our "Getting Started with Digital Power Monitors" app note, found at: https://www.ti.com/lit/an/sboa511a/sboa511a.pdf.

    This document even has a link to a excel design tool that can help you pick the shunt and calculate the calibration register for you.