ZHCSK66C January 2014 – August 2019 ADS1283
PRODUCTION DATA.
The last stage of the ADS1283 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 cutoff frequency. The transfer function for the filter is shown in Equation 11:
The high-pass corner frequency is programmed by registers HPF[1:0], in hexadecimal. Equation 13 is used to set the high-pass corner frequency. Table 11 lists example values for the high-pass filter.
where
| fHP (Hz) | DATA RATE (SPS) | HPF[1:0] |
|---|---|---|
| 0.5 | 250 | 0337h |
| 1.0 | 500 | 0337h |
| 1.0 | 1000 | 019Ah |
The HPF causes a small gain error, in which case the magnitude of the error depends on the ratio of fHP / fDATA. For many common values of (fHP / fDATA), the gain error is negligible. Figure 43 shows the gain error of the HPF.
Figure 43. HPF Gain Error The gain error factor is illustrated in Equation 14:
Figure 44 shows the first-order amplitude and phase response of the HPF. In the case of applying step inputs or synchronizing, make sure to take the settling time of the filter into account.
Figure 44. HPF Amplitude and Phase Response