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INA219: small resistor causes calibration register value over 32768

Ann_Lien
Genius 14530 points
Part Number: INA219

Hi expert,

My customer use INA219 at their server application and condition is shown below.

  • maximum current = 10A.
  • Rshunt=2mohm.
  • Vshunt_max=20mV.
  • current LSB = 305*10^6.
  • calibration register = 67108.

67108 is over 32768 so we cannot fill in calibration register. Do we have resistor limitation which causes calibration register value over 32768? Thanks a lot!!

Best regards,

Ann Lien

  • 0
    TI__Mastermind 26335 points
    Hello Ann,
    Thanks for reaching out on the forum. Based on your customer’s settings, their current_LSB is beneath the resolution capability of the IC. This device uses the shunt voltage to determine the current. According to your stated conditions, if we use the calculated current_LSB, the calculated vshunt voltage is beneath the vshunt_LSB value of 10uV stated in the datasheet. Despite this limitation you can still scale a desired measurement range to set the min and max of the current register. However, this scaling also has a limitation based on the calibration register, current_LSB, and shunt resistor. According to our EVM GUI, you should be able to reach 65535 (2^16-1) for this calibration register. Based off of this value you need to either adjust your current range or your shunt value. Assuming we keep the current range, we would need to ajust the shunt to =0.04096/(305.18uA*65535)=2.048mohm. As this is not a standard shunt value and board manufacturing may also be vary (trace depth and width), you may want to use the next largest shunt with a tight tolerance and adjust your current range accordingly.