LTC2410 Linear Technology, LTC2410 Datasheet - Page 30

• Manufacturer Part Number: LTC2410
• Description: 24-Bit No Latency ADC with Differential Input and Differential Reference
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
LTC2410
front of the LTC2410, the input dynamic current should be
considered (see Input Current section). In cases where
large effective RC time constants are used, an external
buffer amplifier may be required to minimize the effects of
dynamic input current.
Traditional high order delta-sigma modulators, while pro-
viding very good linearity and resolution, suffer from po-
tential instabilities at large input signal levels. The propri-
etary architecture used for the LTC2410 third order modu-
lator resolves this problem and guarantees a predictable
stable behavior at input signal levels of 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 LTC2410 is eminently
suited for such tasks. When the perturbation is differential,
the specification of interest is the normal mode rejection
30
U
U
–100
–120
–100
–120
Figure 43. Measured Input Normal Mode Rejection vs Input Frequency
Figure 42. Measured Input Normal Mode Rejection vs Input Frequency
– 60
– 60
–20
–40
–80
–20
–40
–80
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
W
30
45
60
U
75
90
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
105 120 135 150 165 180 195 210 225 240
for large input signal levels. With a reference voltage
V
range of 5V peak-to-peak. Figures 42 and 43 show mea-
surement results for the LTC2410 normal mode rejection
ratio with a 7.5V peak-to-peak (150% of full scale) input
signal superimposed over the more traditional normal mode
rejection ratio results obtained with a 5V peak-to-peak (full
scale) input signal. In Figure 42, the LTC2410 uses the
internal oscillator with the notch set at 60Hz (F
and in Figure 43 it uses the internal oscillator with the
notch set at 50Hz (F
rejection performance is maintained with no compromises
in this extreme situation. When operating with large input
signal levels, the user must observe that such signals do
not violate the device absolute maximum ratings.
V
V
(150% OF FULL SCALE)
V
V
(150% OF FULL SCALE)
REF
IN(P-P)
IN(P-P)
IN(P-P)
IN(P-P)
= 5V, the LTC2410 has a full-scale differential input
= 5V
= 7.5V
= 5V
= 7.5V
O
V
REF
REF
V
F
T
V
REF
REF
V
F
T
= HIGH). It is clear that the LTC2410
O
O
A
A
CC
INCM
CC
INCM
= GND
= 25 C
= 5V
= 25 C
+
–
+
–
= 5V
= 5V
= 5V
= 5V
= GND
= GND
= 2.5V
= 2.5V
2410 F3a
2410 F4a
O
= LOW)