CDB4328 International Power Sources, Inc., CDB4328 Datasheet - Page 14

• Manufacturer Part Number: CDB4328
• Description: 18-bit, Stereo D/A Converter For Digital Audio
• Manufacturer: International Power Sources, Inc.

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-
su lting from the n oise shaping process
(Figure 25). The switched-capacitor stage scales
with the master clock signal being applied to the
14
Figure 25. Spectrum After Switched-Capacitor Filter
Figure 26. Spectrum After Continuous Time Filter
(dB)
(dB)
24
24
64Fs
f (kHz)
f (kHz)
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.
-12
-16
-20
-4
-8
20
16
12
8
4
0
0
Figure 27. Deviation From Linear Phase
2
4
6
Frequency (kHz)
8
10
12
Analog Filter
Digital Filter
CS4328
14
Total Phase
16
DS62F3
18
20