ZHCSES1B March 2016 – October 2018 ADS1282-SP
PRODUCTION DATA.
The last stage of the ADS1282-SP filter block is a first-order HPF implemented as an IIR structure. This filter stage blocks DC signals and rolls off low-frequency components below the cut-off frequency. The transfer function for the filter is shown in Equation 17 of the 器件支持.
The high-pass corner frequency is programmed by registers HPF[1:0], in hexadecimal. Equation 10 is used to set the high-pass corner frequency. Table 8 lists example values for the high-pass filter.
where
| ƒHP (Hz) | DATA RATE (SPS) | HPF[1:0] |
|---|---|---|
| 0.5 | 250 | 0337h |
| 1 | 500 | 0337h |
| 1 | 1000 | 019Ah |
The HPF causes a small gain error, in which case the magnitude of the error depends on the ratio of ƒHP/ƒDATA. For many common values of (ƒHP/ƒDATA), the gain error is negligible. Figure 44 shows the gain error of the HPF. The gain error factor is illustrated in Equation 16 (see 器件支持).
Figure 44. HPF Gain Error Figure 45 shows the first-order amplitude and phase response of the HPF. In the case of applying step inputs or synchronizing, the settling time of the filter should be taken into account.
Figure 45. HPF Amplitude and Phase Response