CS4328 Datasheet, PDF (14/31 Pages) Cirrus Logic – 18-Bit, Stereo D/A Converter for Digital Audio

CS4328
capacitor, where the polarity of each packet is
controlled by the 1-bit signal. The result is a
1-bit D/A conversion process that is very insensi-
tive to clock jitter. This is a major improvement
over previous generations of 1-Bit D/A convert-
ers where the magnitude of charge in the D/A
process is determined by switching a current ref-
erence for a period of time defined by periods of
the master clock.
The final stage of the CS4328 is made up of a
5th order switched-capacitor low pass filter and a
2nd order continuous time filter. The switched-
capacitor filter eliminates out-of-band energy re-
sulting from the noise shaping process
(Figure 25). The switched-capacitor stage scales
with the master clock signal being applied to the
CS4328. The final stage is a 2nd order continu-
ous time filter that eliminates high frequency
energy that appears at multiples of the 64× Fs
sample rate (Figure 26).
Figures 27-30 are computer simulations of the
combined response of the CS4328 digital and
analog filters with an input word rate of 48 kHz.
Figure 27 shows the individual and combined
phase response of the CS4328 filters. Notice the
digital filter equalization of the analog filter to
produce a linear phase response.
Figures 28-30 are plots of the CS4328 magni-
tude response.
(dB)
24
64Fs f (kHz)
Figure 25. Spectrum After Switched-Capacitor Filter
(dB)
24
f (kHz)
Figure 26. Spectrum After Continuous Time Filter
20
16
12
Analog Filter
8
4
Total Phase
0
-4
-8
Digital Filter
-12
-16
-20
0 2 4 6 8 10 12 14 16 18 20
Frequency (kHz)
Figure 27. Deviation From Linear Phase
14
DS62F3