PCM1604 BURR-BROWN [Burr-Brown Corporation], PCM1604 Datasheet - Page 30

• Manufacturer Part Number: PCM1604
• Description: 24-Bit, 192kHz Sampling,6-Channel, Enhanced Multi-Level, Delta-Sigma DIGITAL-TO-ANALOG CONVERTER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

FIGURE 20. Quantization Noise Spectrum.
FIGURE 19. Eight-Level Delta-Sigma Modulator.
THEORY OF OPERATION
The D/A converter section of the PCM1604 is based upon a
multi-bit delta-sigma architecture. This architecture utilizes
an 4
an analog low-pass filter. A block diagram of the delta-sigma
modulator is shown in Figure 19. This architecture has the
advantage of stability and improved jitter tolerance when
compared to traditional 1-bit (2-level) delta-sigma designs.
The combined oversampling rate of the digital interpolation
filter and the delta-sigma modulator is 32fs, 64fs, or 128fs.
The total oversampling rate is determined by the desired
sampling frequency. If fs
Register 12 may be set to an oversampling rate to 64fs or
128fs. If fs > 96kHz, then the OVER bit may be used to set the
oversampling rate to 32fs or 64fs. Figure 20 shows the out-
of- band quantization noise plots for both the 64x and 128x
oversampling scenarios. Notice that the 128x oversampling
plot shows significantly improved out-of-band noise perfor-
mance, allowing for a simplified low-pass filter to be used at
the output of the DAC.
th
–100
–120
–140
–160
–180
-order noise shaper and an 8-level quantizer, followed by
–20
–40
–60
–80
0
0
4f
S
®
or 8f
1
PCM1604, PCM1605
S
QUANTIZATION NOISE SPECTRUM
2
+
(64x Oversampling)
3
Frequency (f
Z
–1
96kHz, then the OVER bit in
4
S
)
5
6
+
7
Z
–1
8
30
8-Level Quantizer
Figure 21 illustrates the simulated jitter sensitivity of the
PCM1604. To achieve best performance, the system clock
jitter should be less than 300 picoseconds. This is easily
achieved using a quality clock generation IC, like Burr-
Brown’s PLL1700.
FIGURE 21. Jitter Sensitivity.
–100
–120
–140
–160
–180
+
+
+
–20
–40
–60
–80
125
120
115
110
105
100
–
0
32f
95
90
85
80
0
S
0
, 64f
Z
–1
S
, or 128f
1
100
QUANTIZATION NOISE SPECTRUM
2
S
(128x Oversampling)
200
3
Frequency (f
CLOCK JITTER
+
Jitter (ps)
4
300
Z
–1
S
)
5
400
6
500
7
8
600