SLYA042 July   2024 FDC1004 , FDC1004-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 CSAs and Input Bias Stage
  6. 3 CSA and Gain Error Factor
  7. 4 Applications for Resistance at Input Pins of Current Sense Amplifiers
    1. 4.1 Input Resistance Design Considerations
  8. 5 Applications for Input Resistance at Reference Pins of Current Sense Amplifiers
    1. 5.1 Bidirectional CSA and Applications
    2. 5.2 Driving CSA Reference Pin With High-Resistance Source Voltage
    3. 5.3 Input Resistance at Reference Pin Design Considerations
  9. 6 Design Procedure and Error Calculation for External Input Resistance on CSA
    1. 6.1 Calculating eEXT for INA185A4 With 110Ω Input Resistors
  10. 7 Design Procedure for Input Resistance on Capacitively-Coupled Current Sense Amplifier
    1. 7.1 Bench Verification of Input eEXT for Capacitively-Coupled Current Sense Amplifiers
  11. 8 Design Procedure for Input Resistance at CSA Reference Pins
  12. 9 Input Resistance Error Test with INA185 Over Temperature
    1. 9.1 Schematic
    2. 9.2 Methods
    3. 9.3 Theoretical Model
    4. 9.4 Data for INA185A4 with 110Ω Input Resistors
      1. 9.4.1 Data Calculations
    5. 9.5 Analysis
  13. 10Input Resistance Error Test with INA191 Over Temperature
    1. 10.1 Schematic
    2. 10.2 Methods
    3. 10.3 Theoretical Model
    4. 10.4 Data for INA191A4 With 2.2kΩ Input Resistors
      1. 10.4.1 Data Analysis
    5. 10.5 Analysis
  14. 11Derivation of VOS, EXT for a Single Stage Current Sense Amplifier (CSA)
  15. 12Summary
  16. 13References

10.3 Theoretical Model

For CSA with capacitive-coupled inputs, the best way to calculate error is to determine RDIFF at each operating temperature using data sheet plots and then use the GEF equation to understand how gain can attenuate. Section 7.

A theoretical model was considered using parameters below. The RDIFF values from the data sheet and the device's measured gain (GDevice, measured) at each temperature were entered. The predicted total gain (GTotal, predicted) was calculated using:

Equation 23. GTotal, predicted = (GainCSA, Measured)×GEF
Table 10-2 Prediction Model Parameters Over Temperature
TA (°C)-4025125
RSH (Ω)0.997891.001161.0015
RF (Ω)2.20E+032.20E+032.20E+03
RDIFF, Typical (Ω)3.20E+062.75E+062.55E+06
EG, EXT (%)-0.137%-0.160%-0.172%
EG, EXT Drift (ppm/°C)-3.45-2.12-1.25
GDevice, measured199.66932199.86724200.23399
GTotal, predicted199.3950856199.547887199.8890043
EG, EXT predicted (%)0.022%0%-0.013%