LTC2492_15 Datasheet, PDF (31/38 Pages) Linear Technology – 24-Bit 2-/4-Channel ADC with Easy Drive Input Current Cancellation

LTC2492
Applications Information
0
–20
MEASURED DATA
CALCULATED DATA
V_CC = 5V
V_REF = 5V
V_IN(CM) = 2.5V
V_IN(P-P) = 5V
– 40
T_A = 25°C
– 60
– 80
–100
–120
0
15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240
INPUT FREQUENCY (Hz)
2492 F22
Figure 22. Input Normal Mode Rejection vs Input Frequency with
Input Perturbation of 100% (60Hz Notch)
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.
0
–20
MEASURED DATA
CALCULATED DATA
V_CC = 5V
V_REF = 5V
V_IN(CM) = 2.5V
V_IN(P-P) = 5V
–40
T_A = 25°C
–60
–80
–100
–120
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
INPUT FREQUENCY (Hz)
2492 F23
Figure 23. Input Normal Mode Rejection vs Input Frequency with
Input Perturbation of 100% (50Hz Notch)
0
–20
V_IN(P-P) = 5V
V_IN(P-P) = 7.5V
(150% OF FULL SCALE)
V_CC = 5V
V_REF = 5V
V_IN(CM) = 2.5V
T_A = 25°C
– 40
– 60
– 80
–100
–120
0
15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240
INPUT FREQUENCY (Hz)
2492 F25
Figure 25. Measure Input Normal Mode Rejection vs Input
Frequency with Input Perturbation of 150% (60Hz Notch)
0
–20
MEASURED DATA
CALCULATED DATA
V_CC = 5V
V_REF = 5V
V_IN(CM) = 2.5V
V_IN(P-P) = 5V
– 40
T_A = 25°C
– 60
– 80
–100
–120
0
20 40 60 80 100 120 140 160 180 200 220
INPUT FREQUENCY (Hz)
2492 F24
Figure 24. Input Normal Mode Rejection vs Input Frequency with
Input Perturbation of 100% (50Hz/60Hz Notch)
0
–20
V_IN(P-P) = 5V
V_IN(P-P) = 7.5V
(150% OF FULL SCALE)
V_CC = 5V
V_REF = 5V
V_IN(CM) = 2.5V
T_A = 25°C
– 40
– 60
– 80
–100
–120
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
INPUT FREQUENCY (Hz)
2492 F26
Figure 26. Measure Input Normal Mode Rejection vs Input
Frequency with input Perturbation of 150% (50Hz Notch)
For more information www.linear.com/LTC2492
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