Ultra-low-latency decimation filters have the smallest group delay (around 3–4 samples at output sample rate) but have larger group delay deviations than low-latency filters. The out-of-band attenuation is greater than 85 dB for ultra-low-latency filters. Figure 3-4 shows the ultra-low-latency frequency response for the 48-kHz sample rate. The magnitude response for the ultra-low-latency filters are nearly identical to the low-latency filters. Ultra-low-latency filters having lower group delay but higher phase deviation. Figure 3-5 shows the phase deviation of the 48 kHz sample rate filter. The phase deviation is not very large (less than 14.5 degrees and greater than -10.3 degrees) for frequencies less than 0.3 × fs. Ultra-low-latency filters are suitable for applications that require extremely fast conversion but can tolerate small amounts of phase deviation.

Figure 3-4 Ultra-Low-Latency Decimation Filter Response

Figure 3-5 Ultra-Low-Latency Decimation Filter Phase Deviation