LTC2411CMS Linear Technology, LTC2411CMS Datasheet - Page 33

• 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
Averaging 64 samples however reduces the noise level by
a factor of eight, bringing the resolving power to 1 part in
40000, comparable to better weighing systems. Hyster-
esis and creep effects in the load cells are typically much
greater than this. Most applications that require strain
measurements to this level of accuracy are measuring
slowly changing phenomena, hence the time required to
average a large number of readings is usually not an issue.
For those systems that require accurate measurement of
a small incremental change on a significant tare weight,
the lack of history effects in the LTC2400 family is of great
benefit.
For those applications that cannot be fulfilled by the
LTC2411/LTC2411-1 alone, compensating for error in
external amplification can be done effectively due to the
“no latency” feature of the LTC2411/LTC2411-1. No
latency operation allows samples of the amplifier offset
and gain to be interleaved with weighing measurements.
The use of correlated double sampling allows suppres-
sion of 1/f noise, offset and thermocouple effects within
the bridge. Correlated double sampling involves alternat-
ing the polarity of excitation and dealing with the reversal
of input polarity mathematically. Alternatively, bridge
excitation can be increased to as much as 10V, if one of
several precision attenuation techniques is used to pro-
duce a precision divide operation on the reference signal.
U
U
BRIDGE
R1 AND R2 CAN BE USED TO INCREASE TOLERABLE AC COMPONENT ON REF SIGNALS
350
W
R1
R2
Figure 40. Simple Bridge Connection
U
2
3
4
5
REF
REF
IN
IN
LTC2411-1
+
–
LTC2411/
+
–
GND
V
CC
1
6
SDO
SCK
Another option is the use of a reference within the 5V input
range of the LTC2411/LTC2411-1 and developing excita-
tion via fixed gain, or LTC1043 based voltage multiplica-
tion, along with remote feedback in the excitation
amplifiers, as shown in Figures 45 and 46.
Figure 40 shows an example of a simple bridge connec-
tion. Note that it is suitable for any bridge application
where measurement speed is not of the utmost impor-
tance. For many applications where large vessels are
weighed, the average weight over an extended period of
time is of concern and short term weight is not readily
determined due to movement of contents, or mechanical
resonance. Often, large weighing applications involve load
cells located at each load bearing point, the output of
which can be summed passively prior to the signal pro-
cessing circuitry, actively with amplification prior to the
ADC, or can be digitized via multiple ADC channels and
summed mathematically. The mathematical summation
of the output of multiple LTC2411/LTC2411-1’s provide
the benefit of a root square reduction in noise. The low
power consumption of the LTC2411/LTC2411-1 make it
attractive for multidrop communication schemes where
the ADC is located within the load-cell housing.
A direct connection to a load cell is perhaps best incorpo-
rated into the load-cell body, as minimizing the distance to
CS
F
O
8
9
7
10
+
LT1019
LTC2411/LTC2411-1
2411 F40
33