JAJSLQ5C April 2021 – September 2022 ADS127L11
PRODUCTION DATA
The following figures are produced by the TINA-TI™, SPICE-based analog simulation program. The THS4551 SPICE model can be downloaded at the THS4551 product folder.
Figure 9-2 shows the frequency response of the antialias filter and the total response of the antialias filter and ADC. As shown in this image, the filter provides 90-dB stop-band attenuation from the Nyquist frequency to the 12.8-MHz fMOD frequency.
Figure 9-3 shows the analog filter group delay. The 0.575-μs group delay is small in comparison to the 85-μs group delay of the ADC digital filter (34 / fDATA). The analog filter group delay linearity is 0.017 μs, peaking at the edge of the 165-kHz pass band.
Figure 9-4 shows the noise density of the antialias filter circuit, the noise density of the ADC, and the combined noise density of the filter and ADC. Noise density is the noise voltage per √Hz of bandwidth plotted versus frequency.
Figure 9-5 shows the total noise from the 1-Hz start frequency up to the ADC final bandwidth. Below 200 Hz, noise is dominated by 1 / f voltage and current noise of the THS4551 amplifier. Above 200 Hz, noise is dominated by ADC noise. The combined noise of the filter and ADC over the 165-kHz bandwidth is 11.8 μV, meeting the 12-μV target value.