SBAS886A October 2020 – May 2022 ADC3641 , ADC3642 , ADC3643
PRODUCTION DATA
The ADC364x includes an optional on-chip digital down conversion (DDC) decimation filter that can be enabled via SPI register setting. It supports complex decimation by 2, 4, 8, 16 and 32 using a digital mixer and a 32-bit numerically controlled oscillator (NCO) as shown in Figure 8-20. Furthermore it supports a mode with real decimation where the complex mixer is bypassed (NCO should be set to 0 for lowest power consumption) and the digital filter acts as a low pass filter.
Internally the decimation filter calculations are performed with a 20-bit resolution in order to avoid any SNR degradation due to quantization noise. The Section 8.3.5.4 truncates to the selected resolution prior to outputting the data on the digital interface.