CS4328 datasheet(10/31 Pages) CIRRUS

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Performance Plots

The following collection of CS4328 measure-

ment plots (IWR = 48 kHz) were taken with an

Audio Precision Dual Domain System One. All

FFT plots are 16,384 point.

Figure 9 shows the frequency response with a

48 kHz input word rate. The response is very flat

out to half the input word rate.

Figure 10 shows the muted noise with all zeros

data into the CS4328. This plot is dominated by

the noise floor of the System One.

Figure 11 shows the unmuted noise. This data

was taken by feeding the CS4328 continuous ze-

ros, but pulling CALI low. This unmutes the

output stage of the CS4328. This plot shows the

noise shaping characteristics of the delta-sigma

modulator combined with the analog filter.

Figure 12 shows the A-weighted THD+N vs sig-

nal amplitude for a dithered 1kHz input signal.

Notice that there is no increase in distortion as

the signal level decreases. This indicates very

good low-level linearity, one of the key benefits

of the delta-sigma technique.

Figure 13 shows the fade-to-noise linearity test

result using track 20 of the CBS CD-1. The in-

put test signal is a dithered 500 Hz sine wave

which gradually fades from -60 dB level to -120

dB. During the fading, the output level from the

CS4328 is measured and compared to the ideal

level. Notice the very close tracking of the out-

put level to the ideal, even at low level inputs of

-90 dB. The gradual shift of the plot away from

zero at signal levels < -100 dB is caused by the

background noise starting to dominate the meas-

urement.

Figure 14 shows the impulse response, taken

from the single positive full scale value on track

17 of the CD-1 test disk. Notice the high degree

of symmetry, indicating good phase linearity.

Figure 15 shows a 16K FFT plot result, with a

1 kHz -90 dB dithered input. Notice the com-

plete lack of distortion components and tones.

Figure 16 shows a bandlimited, 10 Hz to

22 kHz, time domain plot of the CS4328 output

with a 1 kHz, -90 dB dithered input. Notice the

clear residual sine wave shape, in the presence of

noise.

Figure 17 shows the monotonicity test result

plot. The input data to the CS4328 is +1 LSB, -1

LSB four times, then +2 LSB, -2 LSB four times

and so on, until +10 LSB, -10 LSB. This data

pattern is taken from track 21 of the CD-1 test

disk. Notice the increasing staircase envelope,

with no decreasing elements. Notice also the

clear resolution of the LSB. For this test, one

LSB is a 16-bit LSB.

The following tests were done by filtering the

analog output of the CS4328 with the System

One analyzer 1 kHz notch filter to reduce the

peak signal level. The resulting signal was then

amplified and applied to the DSP module, avoid-

ing distortion in the System One A/D converter.

Figure 18 shows a 16K FFT Plot with a 1 kHz,

0 dB input. Notice the low order harmonic dis-

tortion at < -100 dB.

Figure 19 shows a 16K FFT Plot with a 1 kHz,

-10 dB input. Notice the almost complete ab-

sence of distortion, with a small residual 2nd

harmonic at -110 dB.

CS4328

DS62F3

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