SBOA443 March   2021 INA293

 

  1.   Trademarks
  2. 1Introduction
  3. 2The SAR ADC Switching Model
    1. 2.1 Acquisition Time
    2. 2.2 ADC Resolution
    3. 2.3 Sample Rate
  4. 3The ADC Charge Bucket Filter
    1. 3.1 The Filter Capacitor, CFILT
    2. 3.2 Output Filter Resistor, RFILT
  5. 4Output Filter Discussion and Design
    1. 4.1 INA293 With the ADC Switching Model
  6. 5Summary
  7. 6References

5 Summary

From the discussion of these various topics above, it shows that an algorithm may be established to help in the realization of designing a charge filter for a current shunt amplifier using the following steps:

  1. Choose the current sense amplifier that is correct for your application.
  2. Determine the digital sampling requirements of your system, and shortlist possible ADCs that may work for the intended design. Important parameters to note are default acquisition time, sample and hold capacitance, and resolution.
  3. Use the bandwidth of the amplifier, resolution of the ADC, and the assumption of voltage droop to approximate the minimum needed acquisition time.
  4. Either select a device with the appropriate acquisition time, or identify if the ADC chosen has the ability to extend acquisition time via the use of an external clock.
  5. Determine the potential range of values for CFILT based on the CSH value of the chosen converter. This can quickly be achieved using the Analog Engineer's Calculator.
  6. With the value of CFILT, calculate the needed value of RFILT.
  7. Ensure that the chosen value of RFILT is greater than the minimum required calcuation for stability based on the amplifiers output impedance.
  8. Simulate the designed system using the created switching model to ensure proper settling inside the designed parameters. Iterative analysis of RFILT can help achieve additional accuracy if necessary.