XTR108EA-2K5 BURR-BROWN [Burr-Brown Corporation], XTR108EA-2K5 Datasheet - Page 8

• Manufacturer Part Number: XTR108EA-2K5
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

TYPICAL CHARACTERISTICS
At T
OVERVIEW
The XTR108 is a 4-20mA current-loop transmitter that
allows the user to digitally adjust the gain, offset, and
linearity correction of the analog output to calibrate the
sensor. The digital data for adjustment are stored in an
external EEPROM device.
The analog signal path is composed of a compound multi-
plexer (MUX), programmable gain instrumentation amplifier
(PGA), and an output current amplifier. Analog support func-
tions include digitally controlled current sources for sensor
excitation, PGA offset control, linearization, voltage refer-
ence, and voltage regulator.
The digital interface communicates with external devices for
calibration and to store the resultant data in an SPI compat-
ible EEPROM. A complete system is shown in Figure 1. The
XTR108 serial interface is SPI compatible and only requires
four connections to the calibration controller: a serial clock
(SCLK), a serial data line (SDIO), a chip select line (CS1),
and a ground sense line. All logic signals to the XTR108
must be referenced to the potential of the ground sense line
(I
Within this entire system there may exist three different
“GND” voltage levels. In addition, the voltage difference
between the I
current level. It is not certain that the “GND” potential of the
calibration system will be at the same potential of either the
I
shown in Figure 1. All voltages specified for the XTR108
are with reference to the I
8
RET
RET
A
1000
= +25 C, V+ = 24V, unless otherwise noted. R
or I
100
pin on the XTR108).
10
O
1
potential, and therefore the isolation couplers are
C
FILT
RET
= 0.01
and I
INPUT NOISE POWER DENSITY
10
O
potential will depend on the output
Frequency (Hz)
RET
pin.
100
VI
= 6.34k .
1k
10k
(Cont.)
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FIGURE 1. Complete System Level Configuration with
The XTR108 also needs to communicate with the external
EEPROM device independently from the calibration control-
ler to retrieve the calibration constants during normal opera-
tion. The XTR108 provides a second chip select function
(CS2) for the EEPROM device to facilitate this communica-
tion.
EE PROM
XTR108
Three Unique Ground Voltage Levels.
I
RET
GND
T
X
PGA PEAK-TO-PEAK NOISE (RTI)
I
O
SCLK
SDIO
CS1
5s/div
Couplers
Isolation
R
V
BW: 0.1Hz to 10Hz
GND
Calibration
PS
R
System
X
XTR108
SBOS187C
Calib
GND