Datasheet

LTC2486
30
2486fd
APPLICATIONS INFORMATION
The user can expect to achieve this level of performance
using the internal oscillator, as shown in Figures 22, 23,
and 24. Measured values of normal mode rejection are
shown superimposed over the theoretical values in all
three rejection modes.
Traditional high order delta-sigma modulators suffer from
potential instabilities at large input signal levels. The
proprietary architecture used for the LTC2486 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 LTC2486. From these curves, it is shown that the
rejection performance is maintained even in extremely
noisy environments.
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)
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)
INPUT FREQUENCY (Hz)
0
15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240
NORMAL MODE REJECTION (dB)
2486 F22
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
V
IN(CM)
= 2.5V
V
IN(P-P)
= 5V
T
A
= 25°C
MEASURED DATA
CALCULATED DATA
INPUT FREQUENCY (Hz)
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
NORMAL MODE REJECTION (dB)
2486 F23
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
V
IN(CM)
= 2.5V
V
IN(P-P)
= 5V
T
A
= 25°C
MEASURED DATA
CALCULATED DATA
INPUT FREQUENCY (Hz)
0
20 40 60 80 100 120 140 160 180 200 220
NORMAL MODE REJECTION (dB)
2486 F24
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
V
IN(CM)
= 2.5V
V
IN(P-P)
= 5V
T
A
= 25°C
MEASURED DATA
CALCULATED DATA
INPUT FREQUENCY (Hz)
0
15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240
NORMAL MODE REJECTION (dB)
2486 F25
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
V
IN(CM)
= 2.5V
T
A
= 25°C
V
IN(P-P)
= 5V
V
IN(P-P)
= 7.5V
(150% OF FULL SCALE)
INPUT FREQUENCY (Hz)
0
NORMAL MODE REJECTION (dB)
2486 F26
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
V
IN(CM)
= 2.5V
T
A
= 25°C
V
IN(P-P)
= 5V
V
IN(P-P)
= 7.5V
(150% OF FULL SCALE)
12.5 25 37.5 50 62.5 75 87.5 100 112.5 125 137.5 150 162.5 175 187.5 200