JAJSLQ5C April 2021 – September 2022 ADS127L11
PRODUCTION DATA
Figure 9-1 shows an application of the ADS127L11 used in a precision data acquisition system. The goal of this design is an antialias filter at the ADC input to attenuate out-of-band signals at the modulator sample rate (fMOD). The requirement of the antialias filter is 90-dB attenuation at the critical fMOD frequency (12.8 MHz in high-speed mode) using the OSR = 32 setting in wideband filter mode. The filter is designed for a flat amplitude response and low group delay error within the pass band of the signal.
Table 9-1 lists the target design values and the actual values in this design example.
FILTER PARAMETER | TARGET VALUE | ACTUAL VALUE |
---|---|---|
Voltage gain | 0 dB | 0 dB |
Alias rejection at 12.8 MHz | 90 dB | 90 dB |
–0.1-dB frequency | 250 kHz | 260 kHz |
–3-dB frequency | 500 kHz | 550 kHz |
Amplitude peaking | 20 mdB | 12 mdB |
Group delay linearity | 0.1 μs | 0.017 μs |
Total noise of filter and ADC (165-kHz bandwidth) | 12 μV | 11.8 μV |