XTR103 Burr-Brown Corporation, XTR103 Datasheet - Page 7

• Manufacturer Part Number: XTR103
• Description: 4-20mA Current Transmitter with RTD EXCITATION AND LINEARIZATION
• Manufacturer: Burr-Brown Corporation

FIGURE 2. Operation Without External Transistor.
LOOP POWER SUPPLY
The voltage applied to the XTR103, V+, is measured with
respect to the I
40V. The loop supply voltage, V
voltage applied to the XTR103 according to the voltage drop
on the current sensing resistor, R
drop in the line).
If a low loop supply voltage is used, R
relatively low value to assure that V+ remains 9V or greater
for the maximum loop current of 20mA. It may, in fact, be
prudent to design for V+ equal or greater than 9V with loop
currents up to 34mA to allow for out-of-range input condi-
tions. The typical performance curve “Loop Resistance vs
Loop Power Supply” shows the allowable sense resistor
values for full-scale 20mA.
TABLE I. R
Z
, R
O
G
connection, pin 7. V+ can range from 9V to
, and R
XTR103
–200 C
–100 C
100 C
200 C
300 C
400 C
500 C
600 C
700 C
800 C
T
0 C
MIN
LIN
E
V+
INT
I
O
Resistor Values for Pt100 RTD.
E
10
7
100/81
138/78
175/76
212/73
247/71
280/68
313/66
345/64
375/61
For operation without external
transistor, connect pin 11 to
pin 14. See text for discussion
of performance.
18/90
60/84
100 C
11
14
1105
1287
1211
1137
1066
653
996
930
865
803
743
L
PS
(plus any other voltage
100/167 100/260 100/361 100/469 100/588 100/718 100/860
138/162 138/252 138/349 138/453 138/567 138/691
175/157 175/244 175/337 175/437 175/546
212/152 212/235 212/325 212/422
247/146 247/227 247/313
280/141 280/219
313/136
18/185
60/173
, will differ from the
200 C
0.01µF
1229
1258
1183
1110
1039
838
971
905
841
L
MEASUREMENT TEMPERATURE SPAN T ( C)
must be made a
18/286
60/270
300 C
1251
1229
1155
1083
1013
996
946
881
18/396
60/374
400 C
1087
1249
1201
1127
1056
987
921
18/515
60/487
500 C
1131
1231
1173
1100
1030
962
7
The low operating voltage (9V) of the XTR103 allows
operation directly from personal computer power supplies
(12V 5%). When used with the RCV420 Current Loop
Receiver (Figure 8), load resistor voltage drop is limited to
1.5V.
LINEARIZATION
On-chip linearization circuitry creates a signal-dependent
variation in the two matching current sources. Both current
sources are varied equally according to the following equa-
tion:
This varying excitation provides a 2nd-order term to the
transfer function (including the RTD) which can correct the
RTD’s nonlinearity. The correction is controlled by resistor
R
measurement range. Table I provides the R
resistor values for a Pt100 RTD.
If no linearity correction is desired, do not connect a resistor
to the R
current sources to remain a constant 0.8mA.
ADJUSTING INITIAL ERRORS
Most applications will require adjustment of initial errors.
Offset errors can be corrected by adjustment of the zero
resistor, R
Figure 3 shows another way to adjust zero errors using the
output current adjustment pins of the XTR103. This provides
a minimum of 300 A (typically 500 A) adjustment around
the initial low-scale output current. This is an output current
adjustment which is independent of the input stage gain set
18/645
60/610
600 C
LIN
1152
1207
1145
1073
1003
which is chosen according to the desired temperature
NOTE: Values shown are for a Pt100 RTD.
Double (x2) all values for Pt200.
LIN
18/788
60/746
700 C
1159
1181
1117
1046
(I
(maximum I
Z
R
.
pins (R
in mA, V
I
R1
18/946 18/1120 18/1317
60/895 60/1061
800 C
1158
1155
1089
= I
LIN
R2
R
IN
=
= 0.8 +
900 C
1154
1128
R
= 1.0mA)
R
Z
in volts, R
/R
LIN
). This will cause the excitation
G
(Values are in
1000 C
XTR103
500 • V
1140
R
LIN
LIN
IN
in ohms)
.)
G
, R
Z
and R
LIN
®