CDB5571 Cirrus Logic Inc, CDB5571 Datasheet - Page 24

• Manufacturer Part Number: CDB5571
• Description: DEV BOARD FOR CS5571 W/MUX
• Manufacturer: Cirrus Logic Inc
• Type: A/Dr

Specifications of CDB5571

• Number Of Adc's: 1
• Number Of Bits: 16
• Sampling Rate (per Second): 100k
• Data Interface: Serial
• Inputs Per Adc: 2 Single
• Input Range: 2.4 ~ 4.2 V
• Voltage Supply Source: Dual ±
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: CS5571
• Product: Data Conversion Development Tools
• Conversion Rate: 100 KSPS
• Resolution: 16 bit
• Maximum Clock Frequency: 16 MHz
• Interface Type: SPI
• Supply Voltage (max): 3.3 V
• Supply Voltage (min): - 2.5 V
• For Use With/related Products: CS5571
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant
• Other names: 598-1275; CDB5571-1

Figure 20 illustrates a noise histogram of 4096 samples with the input signal adjusted to almost the exact
center of a code with DITHER on. Figure 21 illustrates a noise histogram of 4096 samples with the input
signal at the center of a code with DITHER off.
Notice that with a signal at the center of a code that the converter outputs the same code over 96% of the
time. Figures 22 and 23 illustrate the noise histogram, DITHER on and then DITHER off with the input
signal at a code boundary. Notice that in the DITHER off case the converter only exhibits two codes of
noise.
3.9 DITHER
From the performance plots, one should conclude that the best AC performance for small signals occurs
with DITHER on. For capturing multiple samples and performing averaging, DITHER should also be on
because the dither will randomize the quantization noise of the converter and provide improved accuracy.
However, if only one conversion is to be taken on a DC input, DITHER should be set to off. With DITHER
off, the converter exhibits only two codes of noise if the signal is at any point other than the exact center
of a code. This means that with DITHER off the converter will nominally yield over 32,000 noise-free
counts.
24
4500
4000
3500
3000
2500
2000
1500
1000
4500
4000
3500
3000
2500
2000
1500
1000
500
500
Figure 20. Noise Histogram, 4096 Samples
Figure 22. Noise Histogram, 4096 Samples
0
0
Dither On, Input at Code Boundary
-2
-2
3
0
Dither On, Code Center
709
-1
58
-1
Output (Codes)
Output (Codes)
Output (Codes)
2624
1953
0
0
2019
751
1
1
9
66
3/25/08
2
2
10:56
4500
4000
3500
3000
2500
2000
1500
1000
500
4500
4000
3500
3000
2500
2000
1500
1000
Figure 21. Noise Histogram, 4096 Samples
500
Figure 23. Noise Histogram, 4096 Samples
0
0
Dither Off, Input at Code Boundary
-2
0
-2
0
Dither Off, Code Center
75
-1
2050
-1
Output (Codes)
Output (Codes)
3940
2046
0
0
81
1
0
1
CS5571
DS768PP1
0
2
0
2