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XTR108
SBOS187C – OCTOBER 2001 – REVISED JULY 2005
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 © 2001-2005, Texas Instruments Incorporated
SPI is a trademark of Motorola, Inc. All other trademarks are the property of their respective owners.
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
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 sensors.
Zero, span, and linearization errors in the analog signal
path can be calibrated via a standard digital serial interface,
eliminating manual trimming. Non-volatile external 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.
X
T
R
1
0
8
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
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.
