I'm trying the PCM5122 DAC (master mode) at different sampling frequencies and configurations. I'm particularly interested in using the high attenuation digital filter as discussed at page 52 of the manual.
The default configuration used on the DAC is the normal filter (page 43 of datasheet) which works as expected.
The following images show what I obtain with normal and high attenuation filter when generating a 1 kHz wave at different sampling frequencies (44.1 kHz and 96 kHz)
As you can see with the normal filter we get spikes in the spectrum at Fs and 2 x Fs as described in figure 35 of the datasheet, everything as expected.
By using the high attenuation interpolation filter I would expect to improve the situation according to figure 62 of the datasheet, the spikes at Fs and 2 x Fs should disappear or, at least, be attenuated.
Unfortunately the spikes with the high interpolation filters are higher than the ones obtained using the normal filter!
Another strange fact I noticed when using a sample frequency of 384 kHz is illustrated in the following pictures
Everything looks good when using 16 bit samples at SCK = 12.288 MHz, but when I increase the clock to 18.432 MHz to send 24 bit samples a spike at Fs/4 appears! (please note that this happens with every sampling frequency when I try to use a configuration with RSCK = 48). I think that also this issue is DSP related.
The DAC settings for each sample frequency I used are taken from table 12 of the datasheet according to the SCK reported in the picture.
I'm sure I'm missing something and I have the feeling that the internal DSP is not working properly and/or is not able to correctly process the signal due to some bad configuration.
Thanks in advance for any help
Regards
Marco
PS
I'm using the DAC with the setup discussed in this post with Dafydd
