This feature can be useful for applications that may desire to cover a larger IF bandwidth range but do not necessarily need the instantaneous bandwidth. By dividing the larger IF bandwidth into narrower “sub-bands” , it is possible to increase the Σ-Δ ADC’s dynamic range for each “sub-band” versus one Σ-Δ ADC setting that tries to cover the entire IF bandwidth. Recall that the dynamic range of a Σ-Δ ADC is a strong function of its oversampling ratio (i.e. OSR= FADC/(2*BW)).
This feature allows the Σ-Δ ADC to store up to four different profile settings that can be quickly recalled within 1 µs via a SPI command without recalibrating the Σ-Δ ADC. Calibration of each of the different profiles occurs during the device initialization phase with each profile consisting of the following different application parameters: BW, FIF, IDAC1FS, and MRGN. To ensure that the JESD204B link is maintained when switching between profile settings, the FADC setting along with the decimation filter and JESD204B settings must remains common.
Figure91. NSD Performance with Narrow-Band Profiles (FIF = 220 MHz, 260 MHz, and 300 MHz, BW = 120 MHz, FADC = 3.2 GHz, LEXT = 27 nH)
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