XR18910 Datasheet, PDF (1/19 Pages) Exar Corporation – 8:1 Sensor Interface Analog Front End

XR18910
8:1 Sensor Interface Analog Front End
Description
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).
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.
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 ±0.5%, 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.
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.
The XR18910 is well suited for industrial and consumer applications
using bridge sensors.
FEATURES
■■ 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 ±0.5% 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
APPLICATIONS
■■ Bridge sensor interface
■■ Pressure and temperature sensors
■■ Strain gauge amplifier
■■ Industrial process controls
■■ Weigh scales
Typical Application
V_CC
V_DD
6.8μF
+
6.8μF
+
BRIDGE 8
BRIDGE 1
0.1μF
BRDG VCC
0.1μF
VDD
LDO
IN8+
0.1μF
IN8-
INA /
OUT 10k
PGA
ADC
µC
8:1
MUX
IN1+
IN1-
±560mV
OFFSET TRIM
10-BIT
DAC
PGA
I2C
CONTROL
V_DD
4.7k
SDA
SCL
10nF
V_DD
4.7k
XR18910
AGND
DGND
Figure 1. Typical Application
REV1A
2.5
2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
0
2
4
6
8
10
Time (seconds)
Figure 2. 0.1Hz to 10Hz RTI Voltage Noise
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