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4-20mA, TWO-WIRE TRANSMITTER
“Smart” Programmable with Signal Conditioning
FEATURES
● COMPLETE TRANSMITTER + RTD
LINEARIZATION
● TWO-WIRE, 4-20mA OUTPUT
● VOLTAGE OUTPUT (0.5V to 4.5V)
● ELIMINATES POTENTIOMETERS AND
TRIMMING
● DIGITALLY CALIBRATED
● 5V SUB-REGULATOR OUTPUT
● SERIAL SPI
BUS INTERFACE
● SSOP-24 PACKAGE
SPI is a registered trademark of Motorola.
APPLICATIONS
● REMOTE RTD TRANSMITTERS
● PRESSURE BRIDGE TRANSMITTERS
● STRAIN GAGE TRANSMITTERS
● SCADA REMOTE DATA ACQUISITION
● WEIGHING SYSTEMS
● INDUSTRIAL PROCESS CONTROL
DESCRIPTION
The XTR108 is a “smart”, programmable, 4-20mA, two-
wire transmitter designed for temperature and bridge sen-
sors. Zero, span, and linearization errors in the analog
signal path can be calibrated via a standard digital serial
interface, eliminating manual trimming. Non-volatile ex-
ternal EEPROM stores calibration settings.
The all-analog signal path contains an input multiplexer,
autozeroed programmable-gain instrumentation amplifier,
dual programmable current sources, linearization circuit,
voltage reference, sub-regulator, internal oscillator, control
logic, and an output current amplifier. Programmable level
shifting compensates for sensor DC offsets. Selectable
up- and down-scale output indicates out-of-range and burn-
out per NAMUR NE43. Automatic reset is initiated when
supply is lost.
Current sources, steered through the multiplexer, can be
used to directly excite RTD temperature sensors, pressure
bridges, or other transducers. An uncommitted op amp can
be used to convert current into a voltage. The XTR108 is
specified for –40°C to +85°C.
SBOS187A – OCTOBER 2001
XTR108
www.ti.com
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright © 2001, Texas Instruments Incorporated
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
XTR108
SPI and
Control Circuits
4-20mA
EEPROM
Linearization
Excitation
I
O
I
Ret
Multiplexer
Gain and Offset
SDIO
SCLK
CS2
CS1
V/I-0
V/I-1
V/I-2
V/I-3
V/I-4
V/I-5
RTD
R
1
R
2
R
3
R
4
R
5
PGA V/I
V
PS
R
LOAD
XTR108
