JAJSHL9A June 2019 – January 2021 ADS125H01
PRODUCTION DATA
The finite impulse response (FIR) filter provides simultaneous rejection of 50-Hz and 60-Hz line cycle frequencies and related harmonics at data rates of 2.5 SPS, 5 SPS, 10 SPS, and 20 SPS. The conversion latency of the FIR filter is a single cycle; see Table 9-6 for detailed latency values. As illustrated in Figure 9-6, the FIR filter section receives data from the second-stage sinc filter. The FIR filter section decimates the data to yield the output data rate of 20 SPS. A variable averaging filter (sinc1) yields 10 SPS, 5 SPS, and 2.5 SPS.
As shown in Figure 9-15 and Figure 9-16, the frequency response has nulls that are positioned near 50 Hz and 60 Hz.
Similar to the response of the sinc filter, the overall FIR filter frequency has a low-pass response that rolls off high frequencies. The signal bandwidth depends on the output data rate. Table 9-4 lists the –3-dB filter bandwidth of the FIR filter. The total system bandwidth is the combined response of the digital filter, the PGA antialias filter, and external filters.
DATA RATE (SPS) | –3-dB BANDWIDTH (Hz) |
---|---|
2.5 | 1.2 |
5 | 2.4 |
10 | 4.7 |
20 | 13 |