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XTR115UA

Part # XTR115UA
Description CURRENT LOOP TRANSMITTER 8SOIC - Rail/Tube
Category IC
Availability In Stock
Qty 3
Qty Price
1 + $1.45066
Manufacturer Available Qty
Burr-Brown Corporation
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Technical Document


DISCLAIMER: The information provided herein is solely for informational purposes. Customers must be aware of the suitability of this product for their application, and consider that variable factors such as Manufacturer, Product Category, Date Codes, Pictures and Descriptions may differ from available inventory.

XTR115, XTR116
4
SBOS124A
www.ti.com
TYPICAL PERFORMANCE CURVES
At T
A
= +25°C, V+
= 24V, R
IN
= 20k, and TIP29C external transistor, unless otherwise noted.
10k 100k
Frequency (Hz)
CURRENT GAIN vs FREQUENCY
1M
40
30
20
10
Gain (dB)
C
OUT
= 10nF
R
L
= 250
C
OUT
= 0
R
L
= 0
75 50 25 0 25 50 75 100
Temperature (°C)
REFERENCE VOLTAGE vs TEMPERATURE
125
0.1
0
0.1
0.2
0.3
Reference Voltage (%)
75 50 25 0 25 50 75 100
Temperature (°C)
QUIESCENT CURRENT vs TEMPERATURE
125
260
240
220
200
180
160
Quiescent Current (µA)
(V+) = 36V
(V+) = 24V
(V+) = 7.5V
75 50 250 255075100
Temperature (°C)
OVER-SCALE CURRENT vs TEMPERATURE
125
34
33
32
31
30
29
28
Over-Scale Current (mA)
V+ = 7.5V
V+ = 36V
V+ = 24V
With External Transistor
101 2 3
I
REG
Current (mA)
V
REG
VOLTAGE vs V
REG
CURRENT
4
5.5
5.0
4.5
V
REG
Voltage (V)
+25°C
+25°C
55°C
+125°C
Sinking
Current
Sourcing
Current
55°C
+125°C
XTR115, XTR116
5
SBOS124A
www.ti.com
APPLICATIONS INFORMATION
The XTR115 and XTR116 are identical devices except for
the reference voltage output, pin 1. This voltage is available
for external circuitry and is not used internally. Further
discussions that apply to both devices will refer to the
“XTR115/6.”
Figure 1 shows basic circuit connections with representative
simplified input circuitry. The XTR115/6 is a two-wire
current transmitter. Its input signal (pin 2) controls the output
current. A portion of this current flows into the V+ power
supply, pin 7. The remaining current flows in Q1. External
input circuitry connected to the XTR115/6 can be powered
from V
REG
or V
REF
. Current drawn from these terminals
must be returned to I
RET
, pin 3. This I
RET
pin is a “local
ground” for input circuitry driving the XTR115/6.
The XTR115/6 is a current-input device with a gain of 100.
A current flowing into pin 2 produces I
O
= 100 • I
IN
. The
input voltage at the I
IN
pin is zero (referred to the I
RET
pin).
A voltage input is created with an external input resistor, as
shown. Common full-scale input voltages range from 1V
and upward. Full-scale inputs greater than 0.5V are recom-
mend to minimize the effect of offset voltage and drift of A1.
EXTERNAL TRANSISTOR
The external transistor, Q1, conducts the majority of the full-
scale output current. Power dissipation in this transistor can
approach 0.8W with high loop voltage (40V) and 20mA
output current. The XTR115/6 is designed to use an external
transistor to avoid on-chip thermal-induced errors. Heat
produced by Q1 will still cause ambient temperature changes
that can affect the XTR115/6. To minimize these effects,
locate Q1 away from sensitive analog circuitry, including
XTR115/6. Mount Q1 so that heat is conducted to the
outside of the transducer housing.
The XTR115/6 is designed to use virtually any NPN transis-
tor with sufficient voltage, current and power rating. Case
style and thermal mounting considerations often influence
the choice for any given application. Several possible choices
are listed in Figure 1. A MOSFET transistor will not improve
the accuracy of the XTR115/6 and is not recommended.
R
IN
20k
I
IN
2
V
IN
I
RET
3
XTR115
XTR116
+5V
Regulator
R
2
25
R
LIM
E
5
I
O
4
B
6
V+
7
R
1
2.475k
R
L
V
LOOP
A1
Voltage
Reference
V
REG
5V
V
REF
(1)
8
1
XTR115: 2.5V
XTR116: 4.096V
Possible choices for Q
1
(see text).
2N4922
TIP29C
TIP31B
TYPE
TO-225
TO-220
TO-220
PACKAGE
I = 100
I
IN
I
O
10nF
I
REF
I
IN
All return current
from I
REG
and I
REF
For I
O
= 4mA to 20mA
I
IN
= 40µA to 200µA
With R
IN
= 20k
V
IN
= 0.8V to 4V
I
REG
Q
1
Input
Circuitry
NOTE: (1) See also Figure 5.
FIGURE 1. Basic Circuit Connections.
XTR115, XTR116
6
SBOS124A
www.ti.com
MINIMUM-SCALE CURRENT
The quiescent current of the XTR115/6 (typically 200µA)
is the lower limit of its output current. Zero input current
(I
IN
= 0) will produce an I
O
equal to the quiescent current.
Output current will not begin to increase until I
IN
> I
Q
/100.
Current drawn from V
REF
or V
REG
will add to this minimum
output current. This means that more than 3.7mA is avail-
able to power external circuitry while still allowing the
output current to go below 4mA.
OFFSETTING THE INPUT
A low scale of 4mA is produced by creating a 40µA input
current. This can be created with the proper value resistor
from V
REF
(Figure 2), or by generating offset in the input
drive circuitry.
I
IN
I
RET
XTR115
R
1
2.475k
R
0
62.5k
A1
Voltage
Reference
V
REG
V
REF
2.5V
40µA
0 to 160µA
MAXIMUM OUTPUT CURRENT
The XTR115/6 provides accurate, linear output up to 25mA.
Internal circuitry limits the output current to approximately
32mA to protect the transmitter and loop power/measure-
ment circuitry.
It is possible to extend the output current range of the
XTR115/6 by connecting an external resistor from pin 3 to
pin 5, to change the current limit value. Since all output
current must flow through internal resistors, it is possible to
damage with excessive current. Output currents greater than
45mA may cause permanent damage.
XTR115
XTR116
V
O
D/A
R
IN
V
REF
V
REG
XTR115
XTR116
I
O
D/A
Optical
Isolation
Optical
Isolation
Digital
Control
I
IN
I
RET
V
REF
V
REG
XTR115
XTR116
µC
PWM
Out
Digital
Control
R
IN
Filter
I
RET
V
REG
5V
FIGURE 2. Creating Low-Scale Offset. FIGURE 3. Digital Control Methods.
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