LTC2435-1CGN Linear Technology, LTC2435-1CGN Datasheet - Page 33

• Manufacturer Part Number: LTC2435-1CGN
• Description: IC ADC DIFF I/REF 20BIT 16-SSOP
• Manufacturer: Linear Technology

Specifications of LTC2435-1CGN

• Number Of Bits: 20
• Sampling Rate (per Second): 13.75
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 2
• Power Dissipation (max): 1mW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
As a result of these remarkable normal mode specifica-
tions, minimal (if any) antialias filtering is required in front
of the LTC2435/LTC2435-1. If passive RC components
are placed in front of the LTC2435/LTC2435-1, 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
potential instabilities at large input signal levels. The pro-
prietary architecture used for the LTC2435/LTC2435-1
third order modulator resolves this problem and guaran-
tees 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
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 V
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-
Figure 35. Input Normal Mode Rejection
–100
–120
–40
–60
–80
–20
0
0
f
N
INPUT SIGNAL FREQUENCY (f
U
2f
N
3f
U
N
4f
N
5f
REF
N
W
6f
= 5V, the LTC2435/
N
N
)
7f
N
2435 F35
8f
N
U
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 fre-
quency at 60Hz (F
that the LTC2435/LTC2435-1 rejection performance is
maintained with no compromises in this extreme situa-
tion. When operating with large input signal levels, the
user must observe that such signals do not violate the
device absolute maximum ratings.
Figure 37. LTC2435-1 Input Normal Mode Rejection
Figure 36. Input Normal Mode Rejection
–100
–120
–100
–110
–120
–130
–140
–20
–40
–60
–80
–70
–80
–90
0
248
48
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
LTC2435/LTC2435-1
250
O
50
INPUT SIGNAL FREQUENCY (f
= GND) or 50Hz (F
252 254 256 258 260 262 264
52
54
NO AVERAGE
56
58
RUNNING
AVERAGE
WITH
O
N
60
)
= V
2435 F37
2435 F36
CC
62
). It is clear
33
24351fb