CS5126 Cirrus Logic, CS5126 Datasheet - Page 8

• Manufacturer Part Number: CS5126
• Description: 16-Bit Stereo A/D Converter for Digital Audio
• Manufacturer: Cirrus Logic

Signal
Amplitude
Relative to
Full Scale
Differential Nonlinearity
The self-calibration scheme utilized in the
CS5126 features a calibration resolution of 1/4
LSB, or 18-bits. This ideally yields DNL of
5/4 LSB’s. This insures consistent sound quality
independent of signal level.
Traditional laser trimmed ADC’s have signifi-
cant differential nonlinearities which are disas-
trous to sound quality with low-level signals.
Appearing as wide and narrow codes, DNL
often causes entire sections of the transfer func-
Signal
Amplitude
Relative to
Full Scale
8
1/4 LSB, with code widths ranging from 3/4 to
Figure 4. FFT Plot of CS5126 in Stereo Mode
(Left Channel with 1 kHz, Full-Scale Input)
-100dB
-120dB
-100dB
-120dB
a. Left Channel with 1 kHz, -10 dB Input
-20dB
-40dB
-60dB
-80dB
-20dB
-40dB
-60dB
-80dB
0dB
0dB
1 kHz
1 kHz
Input Frequency
Input Frequency
Figure 5. FFT Plots of CS5126 in Stereo Mode
Sampling Rate: 48 kHz
Full Scale: 9V p-p
S/(N+D): 91.75 dB
S/(N+D): 92.53 dB
Sampling Rate: 48 kHz
Full Scale: 9V p-p
S/(N+D): 83.27 dB
S/(N+D): 84.06 dB
(dc to 20 kHz)
(dc to 20 kHz)
24kHz
24kHz
tion to be missing. Although their affect is minor
on S/(N+D) with high amplitude signals, DNL
errors dominate performance with low-level sig-
nals. For instance, a signal 80dB below full-
scale will slew past only 6 or 7 codes. Half of
those codes could be missing with a conven-
tional hybrid ADC capable of only 14-bit DNL.
The most common source of DNL errors in con-
ventional ADC’s is bit weight errors. These can
arise due to accuracy limitations in factory trim
stations, thermal or physical stresses after cali-
bration, and/or drifts due to aging or temperature
variations in the field. Bit-weight errors have a
drastic effect on a converter’s ac performance.
They can be analyzed as step functions superim-
posed on the input signal. Since bits (and their
errors) switch in and out throughout the transfer
curve, their effect is signal dependent. That is,
harmonic and intermodulation distortion, as well
as noise, can vary with different input condi-
tions.
Differential nonlinearities in successive-approxi-
mation ADC’s also arise due to dynamic errors
in the comparator. Such errors can dominate if
the converter’s throughput/sampling rate is
driven too high. The comparator will not be al-
lowed sufficient time to settle during each bit
decision in the successive-approximation algo-
Signal
Amplitude
Relative to
Full Scale
-100dB
-120dB
b. Left Channel with 1 kHz, -80 dB Input
-20dB
-40dB
-60dB
-80dB
0dB
1 kHz
Input Frequency
Sampling Rate: 48 kHz
Full Scale: 9V p-p
S/(N+D): 13.70 dB
S/(N+D): 14.49 dB
(dc to 20 kHz)
CS5126
DS32F1
24kHz