ZHCSQZ9A March 2022 – October 2022 ADS117L11
PRODUCTION DATA
The sinc4 filter averages and decimates the high-speed modulator data to yield data rates from 1066.6 kSPS to 3.125 kSPS in high-speed mode, and data rates from 133.333 kSPS to 0.390625 kSPS in low-speed mode. Increasing the OSR value decreases the data rate and simultaneously reduces signal bandwidth and total noise resulting from increased decimation and data averaging. Table 8-4 lists the sinc4 filter characteristics.
OSR | DATA RATE (kSPS) | –3-dB FREQUENCY (kHz) | LATENCY TIME (µs)(1) |
---|---|---|---|
HIGH-SPEED MODE (fCLK = 25.6 MHz) | |||
12 | 1066.666 | 242.666 | 4.38 |
16 | 800 | 182 | 5.63 |
24 | 533.333 | 121.333 | 8.13 |
32 | 400 | 91.0 | 10.63 |
64 | 200 | 45.5 | 20.63 |
128 | 100 | 22.75 | 40.63 |
256 | 50 | 11.375 | 80.63 |
512 | 25 | 5.687 | 160.63 |
1024 | 12.5 | 2.844 | 320.63 |
2048 | 6.25 | 1.422 | 640.63 |
4096 | 3.125 | 0.711 | 1280.63 |
LOW-SPEED MODE (fCLK = 3.2 MHz) | |||
12 | 133.333 | 30.333 | 35.04 |
16 | 100 | 22.75 | 45.04 |
24 | 66.666 | 15.166 | 65.04 |
32 | 50 | 11.375 | 85.04 |
64 | 25 | 5.687 | 165.04 |
128 | 12.5 | 2.844 | 325.04 |
256 | 6.25 | 1.422 | 645.04 |
512 | 3.125 | 0.711 | 1285.04 |
1024 | 1.5625 | 0.355 | 2565.04 |
2048 | 0.78125 | 0.177 | 5125.04 |
4096 | 0.390625 | 0.089 | 10245.04 |
Figure 8-14 and Figure 8-15 show the sinc4 filter frequency response at OSR = 32. The frequency response consists of a series of response nulls occurring at discrete frequencies. The null frequencies occur at multiples of fDATA. At the null frequencies, the filter has zero gain. A folded image of the overall frequency response appears at multiples of fMOD, as illustrated in the fMOD frequency plot of Figure 8-15. No attenuation is provided by the filter at input frequencies near n · fMOD (n = 1, 2, 3, and so on), and if present, alias into the pass band.