JAJSG25B August 2018 – April 2020 AMC1035
PRODUCTION DATA.
The modulator generates a bitstream that is processed by a digital filter to obtain a digital word similar to a conversion result of a conventional analog-to-digital converter (ADC). Equation 2 shows a sinc3-type filter, which is a very simple filter, built with minimal effort and hardware:
This filter provides the best output performance at the lowest hardware size (count of digital gates) for a second-order modulator. All the characterization in this document is also done with a sinc3 filter with an oversampling ratio (OSR) of 256 and an output word width of 16 bits.
An example code for implementing a sinc3 filter in an FPGA is discussed in the Combining the ADS1202 with an FPGA Digital Filter for Current Measurement in Motor Control Applications application note, available for download at www.ti.com.