LTC2492 Linear Technology, LTC2492 Datasheet - Page 31

• Manufacturer Part Number: LTC2492
• Description: 24-Bit 2-/4-Channel ADC
• Manufacturer: Linear Technology

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APPLICATIONS INFORMATION
Figure 22. Input Normal Mode Rejection vs Input Frequency with
Input Perturbation of 100% (60Hz Notch)
Figure 23. Input Normal Mode Rejection vs Input Frequency with
Input Perturbation of 100% (50Hz Notch)
Figure 24. Input Normal Mode Rejection vs Input Frequency with
Input Perturbation of 100% (50Hz/60Hz Notch)
–100
–120
–100
–120
–100
–120
–20
–40
–60
–80
–40
–60
–80
–20
–40
–60
–80
–20
0
0
0
0
0
0
12.5 25 37.5 50 62.5 75 87.5 100 112.5 125 137.5 150 162.5 175 187.5 200
15
20
30
40
45
60
60
75
80
90
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
105 120 135 150 165 180 195 210 225 240
100
120
MEASURED DATA
CALCULATED DATA
MEASURED DATA
CALCULATED DATA
MEASURED DATA
CALCULATED DATA
140
160
180
V
V
V
V
T
V
V
V
V
T
V
V
V
V
T
A
CC
REF
IN(CM)
IN(P-P)
A
CC
REF
IN(CM)
IN(P-P)
A
CC
REF
IN(CM)
IN(P-P)
= 25°C
= 25°C
= 25°C
= 5V
= 5V
= 5V
= 5V
= 5V
200
= 5V
= 2.5V
= 2.5V
= 2.5V
= 5V
= 5V
= 5V
2492 F22
2492 F23
2492 F24
220
Traditional high order delta-sigma modulators suffer from
potential instabilities at large input signal levels. The
proprietary architecture used for the LTC2492 third order
modulator resolves this problem and guarantees stability
with input signals 150% of full-scale. In many industrial
applications, it is not uncommon to have microvolt level
signals superimposed over unwanted error sources with
several volts of peak-to-peak noise. Figures 25 and 26
show measurement results for the rejection of a 7.5V
peak-to-peak noise source (150% of full scale) applied
to the LTC2492. From these curves, it is shown that the
rejection performance is maintained even in extremely
noisy environments.
–100
–120
–100
–120
–40
–60
–80
–40
–60
–80
–20
–20
Figure 25. Measure Input Normal Mode Rejection vs Input
Frequency with Input Perturbation of 150% (60Hz Notch)
Figure 26. Measure Input Normal Mode Rejection vs Input
Frequency with input Perturbation of 150% (50Hz Notch)
0
0
0
0
12.5 25 37.5 50 62.5 75 87.5 100 112.5 125 137.5 150 162.5 175 187.5 200
15
30
45
60
75
90
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
105 120 135 150 165 180 195 210 225 240
V
V
(150% OF FULL SCALE)
V
V
(150% OF FULL SCALE)
IN(P-P)
IN(P-P)
IN(P-P)
IN(P-P)
= 5V
= 7.5V
= 5V
= 7.5V
LTC2492
V
V
V
T
V
V
V
T
A
A
CC
REF
IN(CM)
CC
REF
IN(CM)
= 25°C
= 25°C
31
= 5V
= 5V
= 5V
= 5V
= 2.5V
= 2.5V
2492 F25
2492 F26
2492fb