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Calibration register value

Shashank shashank
Prodigy 70 points
Other Parts Discussed in Thread: INA220

If suppose I am using a shunt register of 0.001 Ohms and need an accuracy of .000667A. What is the value of calibration register that I need to choose? Kindly do not redirect me to the Datasheet of the INA220 as I have already read it and has got seriously confused after the same. Kindly give me the direct value.

  • 0
    TI__Expert 4595 points
    Hi Shashank,
    Can you provide the maximum current expected for this application. If the Current LSB needed is 667uA and Rshunt is 1 mohm then using equation 4 in the datasheet the calibration register value to be programmed will be 61409 in decimal. For optimal dynamic range use the maximum expected current for the application and the full scale input range of the device (4 gain options). I will not direct you to the datasheet but please watch our latest video for power settings.
    training.ti.com/getting-started-current-sense-amplifiers-session-15-programming-power-settings
  • 0 in reply to Rabab Itarsiwala
    Prodigy 70 points
    but 61409 means 0xEFE1 , but this seems invalid as the datasheet of ina 220 says that D0 is reserved and should be 0. While writin to D15->D1 of calibration reg do we even consider the D0 bit. My maximum expected current is 1.5 amps. Kindly help ma'am.
  • 0 in reply to Shashank shashank
    TI__Expert 4595 points
    In that case it will probably write 0xEFE0 (61408). But I can double check this. Is using a higher shunt resistor a possibility. With 1 m ohm shunt, at maximum current there is only 1.5 mV input. Dynamic range can be improved if the resistor was chosen based on the Vinput and Maximum current. For example if you choose 40mV full scale and using 1.5 A max current a shunt resistance around 26 m ohm could be chosen. If a current LSB of 45 uA was choosen using equation 2 in the datasheet then configuration register value could be calculated as 35008 (0x88C0) using equation 4.
    Please do watch the video and let me know if you have more questions.