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# INA220: The "OVF" flag in the screenshot, when it is 1, does it mean that the values of registers 01H and 02H are invalid?

Part Number: INA220

Dear TI team，

We use your INA220AIDGSR chip. We have the following problems and would like to seek support.

For example, the "OVF" flag in the screenshot, when it is 1, does it mean that the values of registers 01H and 02H are invalid?

• Hey Cris,

Thank you for posting your question to the E2E Forum.

The math overflow flag (OVF) is set to 1 when the true current value the device is trying to calculate goes beyond the maximum expected current value you chose when determining the calibration value for calibration register (05h). The full-scale range and LSB of the current register (04h) is determined by the value entered into Calibration register. Calibration value is calculated using equation (1) of datasheet.

This is why it is important to define the maximum current you want to measure in your system at any point in time is entered into equation (2) of datasheet where you calculate the Current_LSB given 16-bit resolution.

So if you set Maximum Expected Current to 10A (LSB = 10/(2^15) = 305uA), yet there is 11A running through the shunt resistor, then INA220’s current and power registers will overflow. The current (and power) registers will be trying to process a number greater than what the registers can logically hold. Thus the register values for current and power become invalid. Once this overflow is detected, the OVF flag is set.

Hope this helps.

Sincerely,

Peter Iliya