Datasheet
PCM1741
19
SBAS175
The theoretical quantization noise performance of the
8-level delta-sigma modulator is shown in Figure 15. The en-
hanced multilevel delta-sigma architecture also has advantages
for input clock jitter sensitivity due to the multilevel quantizer,
with the simulated jitter sensitivity, as shown in Figure 16.
KEY PERFORMANCE PARAMETERS
AND MEASUREMENT
This section provides information on how to measure key
dynamic performance parameters for the PCM1741. In all
cases, an Audio Precision System Two Cascade or equivalent
audio measurement system is utilized to perform the testing.
TOTAL HARMONIC DISTORTION + NOISE
Total Harmonic Distortion + Noise (THD+N) is a significant
figure of merit for audio DACs, since it takes into account
both harmonic distortion and all noise sources within a
specified measurement bandwidth. The true rms value of the
distortion and noise is referred to as THD+N. Figure 17
shows the test setup for THD+N measurements.
For the PCM1741, THD+N is measured with a full-scale,
1kHz digital sine wave as the test stimulus at the input of the
DAC. The digital generator is set to a 24-bit audio word
length and a sampling frequency of 44.1kHz or 96kHz. The
digital generator output is taken from the unbalanced
S/PDIF connector of the measurement system. The S/PDIF
FIGURE 16. Jitter Sensitivity.
0 100 200 300 400 500 600
125
120
115
110
105
100
95
90
Dynamic Range (dB)
Jitter (ps)
JITTER DEPENDENCE (64x Oversampling)
FIGURE 17. Test Setup for THD+N Measurements.
S/PDIF
Receiver
Evaluation Board
f
–3dB
= 54kHz or 108kHz
PCM1741
DEM-DAI1741
2nd-Order
Low-Pass
Filter
Notch FilterBand Limit
HPF = 22Hz
LPF = 30kHz
f
C
= 1kHzrms Mode0dBFS,
1kHz Sine Wave
S/PDIF
Output
Analyzer
and
Display
20kHz
Apogee
Filter
Digital
Generator
FIGURE 15. Quantization Noise Spectrum.
012345678
0
–20
–40
–60
–80
–100
–120
–140
–160
–180
Amplitude (dB)
Frequency (f
S
)
QUANTIZATION NOISE SPECTRUM
(64x Oversampling)
QUANTIZATION NOISE SPECTRUM
(128x Oversampling)
012345678
0
–20
–40
–60
–80
–100
–120
–140
–160
–180
Amplitude (dB)
Frequency (f
S
)