The Filter needs some time to process sampled data so max sampling rate depends on filter depths and always less than bus_clk/10.
From Datasheet v.2.30 p. 4:
"The maximum possible sample rate is calculated by dividing the fastest available bus_clk by the number of DFB cycles that will be required by both filters. So, for each of the two channels, calculate a cycle count as follows:
FIR only: 10 + number_of_taps
Biquad even total order only: 13 + 5 × order
Biquad odd total order only: 18 + 5 × order
Both biquad even total order and FIR: 20 + number_of_taps + 5 × order
Both biquad odd total order and FIR: 25 + number_of_taps + 5 × order
Add together the results calculated for the two channels. This is the total number of bus_clk cycles that will be required to execute both channels. Dividing this into the bus_clk frequency will provide the value of the sample rate at which the faster of the two channels will run."
Secondly, where one can find a source of data for sampling at the rate higher than bus_clk/10? The DelSig-ADC can only provide <200kHz (@14-bit).