LTC2411CMS Linear Technology, LTC2411CMS Datasheet - Page 35

• Manufacturer Part Number: LTC2411CMS
• Description: IC A/D CONV 24BIT MICRPWR 10MSOP
• Manufacturer: Linear Technology

Specifications of LTC2411CMS

• Number Of Bits: 24
• Sampling Rate (per Second): 7.5
• 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: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
Note that this 4-amplifier topology has advantages over
the typical integrated 3-amplifier instrumentation ampli-
fier in that it does not have the high noise level common in
the output stage that usually dominates when an instru-
mentation amplifier is used at low gain. If this amplifier is
used at a gain of 10, the gain error is only 10ppm and input
referred noise is reduced to 0.15 V
can also be configured to provide gain of up to 50 with high
gain stability and linearity.
Figure 42 shows an example of a single amplifier used to
produce single-ended gain. This topology is best used in
applications where the gain setting resistor can be made
to match the temperature coefficient of the strain gauges.
If the bridge is composed of precision resistors, with only
one or two variable elements, the reference arm of the
bridge can be made to act in conjunction with the feedback
resistor to determine the gain. If the feedback resistor is
incorporated into the design of the load cell, using resis-
tors which match the temperature coefficient of the load-
cell elements, good results can be achieved without the
need for resistors with a high degree of absolute accuracy.
The common mode voltage in this case, is again a function
of the bridge output. Differential gain as used with a 350
bridge is:
A
V
9 95
.
R
1 175
R
U
1
BRIDGE
R
350
2
+
U
1 F
A
V
Figure 42. Bridge Amplification Using a Single Amplifier
= 9.95 =
RMS
W
. The buffer stages
4.99k
R1
R1 + 175
R1 + R2
3
2
U
–
+
LTC1050S8
5V
7
4
46.4k
R2
0.1 V
6
Common mode gain is half the differential gain. The
maximum differential signal that can be used is 1/4 V
as opposed to 1/2 V
Remote Half Bridge Interface
As opposed to full bridge applications, typical half bridge
applications must contend with nonlinearity in the bridge
output, as signal swing is often much greater. Applications
include RTD’s, thermistors and other resistive elements
that undergo significant changes over their span. For
single variable element bridges, the nonlinearity of the half
175
1 F
+
Figure 43. Remote Half Bridge Interface
20k
20k
PLATINUM
10 F
LTC2411/LTC2411-1
100
25.5k
0.1%
RTD
2
3
4
5
R1
REF
+
1
REF
REF
IN
IN
2
LTC2411-1
+
–
LTC2411/
in the 2-amplifier topology above.
3
+
–
4
GND
V
CC
6
2411 F42
1
0.1 F
2
3
4
5
5V
REF
REF
IN
IN
2.7V TO 5.5V
+
–
+
–
LTC2411-1
LTC2411/
GND
V
V
CC
S
1
6
2411 F43
35
REF
,