Cirrus Logic AN339 - Manual (Page 8)

AN339
AN339REV1
8 AN339REV1
6.3 Dynamic Range Measurements
As discussed in section 5.2 of AES-12id-2006, jitter outside of the baseband frequency range can interact
with the shaped quantization noise of an audio converter and result in decreased dynamic range regardless
of the level or frequency of the audio input signal. The level of dynamic range reduction is dependent upon
the out of band energy of the converter and the out of band jitter signal on its sample clock. Since the pre-
dominant multi-bit converter architectures of today produce less out of band energy than earlier converters
using a single-bit architecture, they can be expected to be less sensitive to out of band jitter.
The measurements reveal that there is little difference between the converter’s dynamic range when
sourced by each recovered clock source. There is a small reduction in dynamic range for the CS8416 and
PDUR = 1 case that can be attributed to the RMCK jitter in the ~100 kHz range as shown in
Figure 7 .
Table 4 summarizes the measurement results.
The plots that follow show the converter’s output
spectrum for each sample rate, both across the
audio band with a -60 dB input stimulus, and out
of the audio band with no input stimulus.
Sample
Rate
CS8414
-
CS8416
PDUR=1
CS8416
PDUR=0 Unit Figure
48 kHz -119.29 -118.64 -119.02 dBr 24
96 kHz -119.36 -119.18 -119.23 dBr 26
192 kHz - - -119.11 dBr 28
Table 4. A-Weighted Dynamic Range Summary
-160
+0
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
d
B
r
A
20k 120k 40k 60k 80k 100k
Hz
-160
+0
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
d
B
r
A
20 20k 50 100 200 500 1k 2k 5k 10k
Hz
Figure 24. FFT - -60 dBFS, 997 Hz
Fs = 48 kHz
Figure 25. FFT - No Input (w/ Dither)
Out of Band, Fs = 48 kHz
CS8414
CS8416 PDUR=0
CS8416 PDUR=1
CS8414
CS8416 PDUR=0
CS8416 PDUR=1
-160
+0
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
d
B
r
A
20k 120k 40k 60k 80k 100k
Hz
-160
+0
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
d
B
r
A
20 20k 50 100 200 500 1k 2k 5k 10k
Hz
Figure 26. FFT - -60 dBFS, 997 Hz
Fs = 96 kHz
Figure 27. FFT - No Input (w/ Dither)
Out of Band, Fs = 96 kHz
CS8414
CS8416 PDUR=0
CS8416 PDUR=1
CS8414
CS8416 PDUR=0
CS8416 PDUR=1