XR18910
8:1 Sensor Interface Analog Front End
Description
FEATURES
The XR18910 is a unique sensor interface integrated circuit with an
onboard 8:1 multiplexer, offset correction Digital-to-Analog Converter
(DAC), instrumentation amplifier and voltage reference. The XR18910
is designed to integrate multiple bridge sensors with a Microcontroller
(MCU) or Field-Programmable Gate Array (FPGA).
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Integrated features for interfacing multiple
bridge sensors with an MCU or FPGA
8:1 differential MUX with I2C interface
Instrumentation amplifier
LDO
Offset correction DAC with I2C interface
( 560mV offset correction range)
Eight selectable voltage gains from 2V/V to
760V/V with only 0.5ꢀ gain error
3mV maximum input offset voltage
100pA maximum input bias current
559μA maximum supply current
2.7V to 5V analog supply voltage range
1.8V to 5V digital supply voltage range
-40°C to 85°C temperature range
3.5mm x 3.5mm QFN-24 package
The integrated offset correction DAC provides digital calibration of the
variable and in many cases substantial offset voltage generated by the
bridge sensors. The DAC is controlled by an I2C compatible 2-wire serial
interface. The serial interface also provides the user with easy controls
to the XR18910’s many functions such as input and gain selection.
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A linear regulator (LDO) provides a regulated voltage to power the input
bridge sensors and is selectable, between 3V and 2.65V. The LDO
current can be sensed and a proportional voltage present at the output
of the IC for monitoring the LDO current.
The XR18910 offers 8 fixed gain settings (from 2V/V to 760V/V), each
with an error of only 0.5ꢀ, that are selectable via the I2C interface.
It also offers less than 3mV maximum input offset voltage, 100pA
maximum input bias current, and 100pA maximum input offset current.
APPLICATIONS
Bridge sensor interface
Pressure and temperature sensors
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The XR18910 is designed to operate from 2.7V to 5V supplies, specified
over the industrial temperature range of -40°C to 85°C and is offered in
a space saving 3.5mm x 3.5mm QFN package. It consumes less than
559μA supply current and offers a sleep mode for added power savings.
Strain gauge amplifier
Industrial process controls
Weigh scales
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The XR18910 is well suited for industrial and consumer applications
using bridge sensors.
Typical Application
m
m
DD
CC
5.8μF
+
5.8μF
+
2.5
2
6.1μF
mDD
6.1μF
BRDG
mCC
6.1μF
16k
1.5
1
BRIDGE 8
LDO
IN8+
IN8-
0.5
0
OUT
INA /
PGA
ADC
µC
-0.5
-1
16nF
8:1
MUX
±±560m
OFFSET TRIM
m
m
DD
DD
-1.5
-2
BRIDGE 1
16-BIT
DAC
PGA
4.7k
4.7k
IN1+
IN1-
SDA
SCL
2
-2.5
I C
CONTROL
0
2
4
6
8
10
Time (seconds)
XR18910
AGND
DGND
Figure 1. Typical Application
Figure 2. 0.1Hz to 10Hz RTI Voltage Noise
REV1A
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