
LTC2435/LTC2435-1
36
24351fc
applicaTions inForMaTion
Figure 40. Measured Input Normal Mode
Rejection vs Input Frequency (fN = 54.6Hz)
INPUT FREQUENCY (Hz)
0
NORMAL
MODE
REJECTION
(dB)
50
100 125
225
2435 F40
25
75
150 175 200
0
–20
–40
–60
–80
–100
–120
VCC = 5V
VREF = 5V
REF– = GND
VINCM = 2.5V
FO = GND
TA = 25°C
VIN(P-P) = 5V
VIN(P-P) = 7.5V
(150% OF FULL SCALE)
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
LTC2435/LTC2435-1 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 VREF = 5V, the LTC2435/
LTC2435-1 have a full-scale differential input range of 5V
peak-to-peak. Figure 40 shows measurement results for
the LTC2435-1 normal mode rejection ratio with a 7.5V
peak-to-peak (150% of full scale) input signal superim-
posed over the more traditional normal mode rejection
ratio results obtained with a 5V peak-to-peak (full scale)
input signal. The same performance is obtained for the
LTC2435 with the frequency scaled to have the notch
frequency at 60Hz (FO = GND) or 50Hz (FO = VCC). It is
clear that the LTC2435/LTC2435-1 rejection performance
is maintained with no compromises in this extreme situ-
ation. When operating with large input signal levels, the
user must observe that such signals do not violate the
device absolute maximum ratings.
Figure 39. Input Normal Mode Rejection
vs Input Frequency with Running Average
INPUT FREQUENCY (Hz)
0
NORMAL
MODE
REJECTION
(dB)
50
100 125
225
2435 F39
25
75
150 175 200
0
–20
–40
–60
–80
–100
–120
VCC = 5V
VREF = 5V
REF– = GND
VINCM = 2.5V
VIN(P-P) = 5V
FO = GND
TA = 25°C
MEASURED DATA
CALCULATED DATA