Datasheet

LTC2411/LTC2411-1
32
APPLICATIO S I FOR ATIO
WUUU
INPUT FREQUENCY (Hz)
0 20 40 60 80 100 120 140 160 180 200 220
NORMAL MODE REJECTION (dB)
2411 F36
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
REF
–
= GND
V
INCM
= 2.5V
V
IN(P-P)
= 5V
F
O
= GND
T
A
= 25°C
MEASURED DATA
CALCULATED DATA
Figure 36. Input Normal Mode Rejection
vs Input Frequency (LTC2411-1)
Figure 37. Measured Input Normal Mode Rejection
vs Input Frequency (LTC2411)
Figure 38. Measured Input Normal Mode Rejection
vs Input Frequency (LTC2411)
up to 150% of full scale. In many industrial applications,
it is not uncommon to have to measure microvolt level
signals superimposed over volt level perturbations and
LTC2411/LTC2411-1 are eminently suited for such tasks.
When the perturbation is differential, the specification of
interest is the normal mode rejection for large input signal
levels. With a reference voltage V
REF
␣ =␣ 5V, the LTC2411/
LTC2411-1 have a full-scale differential input range of 5V
peak-to-peak. Figures 37 and 38 show measurement re-
sults for the LTC2411 normal mode rejection ratio with a
7.5V peak-to-peak (150% of full scale) input signal super-
imposed over the more traditional nor mal mode rejection
ratio results obtained with a 5V peak-to-peak (full scale)
input signal and Figure 39 shows the corresponding mea-
surement result for the LTC2411-1. It is clear that the
LTC2411/LTC2411-1 rejection performance is maintained
with no compromises in this extreme situation. When op-
erating with large input signal levels, the user must ob-
serve that such signals do not violate the device absolute
maximum ratings.
BRIDGE APPLICATIONS
Typical strain gauge based bridges deliver only 2mV/Volt
of excitation. As the maximum reference voltage of the
LTC2411/LTC2411-1 is 5V, remote sensing of applied
excitation without additional circuitry requires that excita-
tion be limited to 5V. This gives only 10mV full scale, which
can be resolved to 1 part in 5000 without averaging. For
many solid state sensors, this is comparable to the sensor.
INPUT FREQUENCY (Hz)
0 15 30 45 60 75 90 105 120 135 150 165 180 195 210
225 240
NORMAL MODE REJECTION (dB)
2411 F37
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
V
INCM
= 2.5V
F
O
= GND
T
A
= 25°C
V
IN(P-P)
= 5V
V
IN(P-P)
= 7.5V
(150% OF FULL SCALE)
Figure 39. Measured Input Normal Mode Rejection
vs Input Frequency (LTC2411-1)
INPUT FREQUENCY (Hz)
0 20 40 60 80 100 120 140 160 180 200 220
NORMAL MODE REJECTION (dB)
2411 F39
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
REF
–
= GND
V
INCM
= 2.5V
F
O
= GND
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)
2411 F38
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
V
REF
= 5V
V
INCM
= 2.5V
F
O
= 5V
T
A
= 25°C
V
IN(P-P)
= 5V
V
IN(P-P)
= 7.5V
(150% OF FULL SCALE)
25 50 75 100 125 150 175 200