3 ADS127Lx1 Delta-Sigma ADC and Digital Filter

The ADS127L11 and ADS127L21 is a family of wide-bandwidth, 24-bit, delta-sigma (ΔΣ) ADCs offering an excellent combination of AC performance and DC precision. These ΔΣ ADCs offer configurable digital filters to optimize for wideband or low latency operation, allowing wideband ac performance or for data throughput dc signals. The ADS127L11 supports data rates up to 400kSPS using the wideband filter and up to 1067kSPS using the low-latency (sinc4) filter. The ADS127L21 supports data rates up to 512kSPS using the wideband filter and up to 1365kSPS using the low-latency (sinc4) filter. The ADS127L21, in addition to the wideband and low latency filter options, it offers programmable infinite and finite impulse response (IIR and FIR) digital filters allowing custom filter profiles.

For a complete table of the available ADS127L21 and ADS127L11 digital filter (wideband, sinc4, sinc3, cascaded sinc3 + sinc1, and cascaded sinc4+sinc1) options, filter bandwidth specifications and noise performance, refer to the ADS127L21 and ADS127L11 device data sheets.

Table 7-6 shows an excerpt of the ADS127L21 sinc4 filter performance. In this example, the ADS127L21 is operated in high-speed mode, oversampling ratio, OSR = 64, sinc4 filter providing a data rate of 200kSPS. This corresponds to an input-referred noise of 5.53µVRMS and a f_–3dB corner frequency of 45.5kHz for the sinc4 filter for these specific settings.