SBAA655A December   2024  – February 2025 ADS127L21 , PGA855 , THS4561

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Anti-Aliasing Filter Design
    1. 2.1 Simulation
    2. 2.2 Hardware Testing
  6. 3Summary
  7. 4References
  8. 5Revision History

2 Anti-Aliasing Filter Design

The schematic shown in Figure 2-1 is a 3rd order low pass filter on ADS127L21EVM-PDK. With the passive components shown, the filter can have a bandwidth around 260kHz. By changing those components shown in red, the cutoff is pushed to over 370kHz. The tolerance of the capacitor and resistors can affect the filter's bandwidth, since the cutoff frequency is determined by the passive components. Changing the capacitors and resistors to 1% and 0.1% tolerances respectively, makes the filter more consistent over natural variations in the components' physical values. A filter design tool can be used to determine the resistor and capacitor values based on the filter's requirements. Texas Instruments' Filter Design Tool can be used to design single-ended filters. See Design Methodology for MFB Filters in ADC Interface Applications for more details on designing a multiple feedback filter.

Anti-Alias Filter Anti-Alias Filter Figure 2-1 Anti-Alias Filter