ZHCSEA4C May 2015 – December 2020 ADS54J40
PRODUCTION DATA
This band-pass decimation filter consists of a digital mixer and three concatenated FIR filters with a combined latency of approximately 28 output clock cycles. The alias band attenuation is approximately
55 dB and the pass-band flatness is ±0.1 dB. By default after reset, the band-pass filter is centered at fS / 16. Using the SPI, the center frequency can be programmed at N × fS / 16 (where N = 1, 3, 5, or 7). Table 8-2 shows corner frequencies for two extreme options.
| CORNERS (dB) | CORNER FREQUENCY AT LOWER SIDE (Center Frequency fS / 16) | CORNER FREQUENCY AT HIGHER SIDE (Center Frequency fS / 16) |
|---|---|---|
| –0.1 | 0.011 × fS | 0.114 × fS |
| –0.5 | 0.010 × fS | 0.116 × fS |
| –1 | 0.008 × fS | 0.117 × fS |
| –3 | 0.006 × fS | 0.120 × fS |
Figure 8-6 and Figure 8-7 show the frequency response of the decimate-by-4 filter for center frequencies fS / 16 and 3 × fS / 16 (N = 1 and N = 3, respectively).
Figure 8-6 Decimate-by-4 Filter Response
Figure 8-7 Decimate-by-4 Filter Response (Zoomed)