SBOA511A March   2021  – September 2021 INA209 , INA219 , INA220 , INA220-Q1 , INA226 , INA226-Q1 , INA228 , INA228-Q1 , INA229 , INA229-Q1 , INA230 , INA231 , INA232 , INA233 , INA234 , INA236 , INA237 , INA237-Q1 , INA238 , INA238-Q1 , INA239 , INA239-Q1 , INA260 , INA3221 , INA3221-Q1

 

  1.   Trademarks
  2. 1 Introduction
  3. 2 Defining Constraints
  4. 3 Find The Maximum Shunt Value
  5. 4 Find The Minimum Shunt Value
  6. 5 Maximum Resolution or Minimum Shunt Loss
  7. 6 What to Do if the Measurement Range Is Insufficient
  8. 7 Determine the Current LSB and Calibration Coefficient
  9. 8 Programming Your Device Registers
  10. 9 Summary
  11. 10Revision History

3 Find The Maximum Shunt Value

The shunt value ultimately determines the current measurement bounds. For a given current range, there may be a range of shunt resistance values that can be used allowing flexibility in your design. The maximum and minimum shunt values need to be calculated, to ensure you choose a shunt that will work for your application. To calculate the max shunt value, you need to look up the shunt voltage input range max listed in the electrical characteristics section of the data sheet. Some devices may have a fixed shunt voltage range as found in the Table 3-1, while others may have ranges that change according to certain register settings such as can be seen in the Table 3-2. One thing to note, is that some devices may have a different name for the shunt voltage input specification. Table 3-3 lists this specification as VDIFF.

Table 3-1 INA226 Shunt Voltage Input Range
Parameter Test Conditions MIN TYP MAX UNIT
INPUT
Shunt voltage input range –81.9175 81.92 mV
Table 3-2 INA219 Shunt Voltage Input Range
Parameter Test Conditions INA219A INA219B UNIT
MIN TYP MAX MIN TYP MAX
INPUT
VSHUNT Full-scale current sense (input) voltage range PGA = /1 0 ±40 0 ±40 mV
PGA = /2 0 ±80 0 ±80 mV
PGA = /4 0 ±160 0 ±160 mV
PGA = /8 0 ±320 0 ±320 mV
Table 3-3 INA229 Shunt Voltage Input Range
Parameter Test Conditions MIN TYP MAX UNIT
INPUT
VDIFF Shunt voltage input range TA=-40°C to +125°C, ADCRANGE=0 -163.84 163.84 mV
TA=-40°C to +125°C, ADCRANGE=1 -40.96 40.96 mV

To find the RSHUNT MAX divide the max shunt input voltage value by your max expected current value.

Equation 1. R SHUNT MAX ≤ Shunt Voltage Input Range MAX I Sense MAX