SX8724C Datasheet, PDF (50/67 Pages) Semtech Corporation – ZoomingADC for sensing data acquisition

ADVANCED COMMUNICATIONS & SENSING
SX8724C
ZoomingADC for sensing data acquisition
DATASHEET
1.2
1
Nelconv = 1
0.8
0.6
0.4
0.2
0
0
0.5
1
1.5
2
2.5
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3.5
4
Normalized Frequency - f x (OSR / fs) [-]
1.2
1
Nelconv = 2
0.8
0.6
0.4
0.2
0
0
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1
1.5
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Normalized Frequency - f x (OSR / fs) [-]
1.2
1.2
1
Nelconv = 4
1
Nelconv = 8
0.8
0.8
0.6
0.6
0.4
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0.2
0.2
0
0
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1
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Normalized Frequency - f x (OSR / fs) [-]
0
0
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1
1.5
2
2.5
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3.5
4
Normalized Frequency - f x (OSR / fs) [-]
Figure 28. Frequency Response. Normalized Magnitude vs. Frequency for Different NELCONV
11.3 Linearity
11.3.1 Integral Non-Linearity
The different PGA stages have been designed to find the best compromise between the noise performance, the
integral non-linearity and the power consumption. To obtain this, the first stage has the best noise performance and
the third stage the best linearity performance. For large input signals (small PGA gains, i.e. up to about 50), the noise
added by the PGA is very small with respect to the input signal and the second and third stage of the PGA should be
used to get the best linearity. For small input signals (large gains, i.e. above 50), the noise level in the PGA is important
and the first stage of the PGA should be used.
The following figures show the Integral non linearity for different gain settings over the chip temperature range
Revision 1.01
© Semtech
January 2011
Page 50
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