Datasheet

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RTD

XTR105

–

4-20 mA

LIN

REG

7.5V to 36V

= 0.8mA

4-20mA CURRENT TRANSMITTER

with Sensor Excitation and Linearization

FEATURES

● LOW UNADJUSTED ERROR

● TWO PRECISION CURRENT SOURCES: 800

A each

● LINEARIZATION

● 2- OR 3-WIRE RTD OPERATION

● LOW OFFSET DRIFT: 0.4µV/°C

● LOW OUTPUT CURRENT NOISE: 30nA

● HIGH PSR: 110dB minimum

● HIGH CMR: 86dB minimum

● WIDE SUPPLY RANGE: 7.5V to 36V

● DIP-14 AND SO-14 PACKAGES

APPLICATIONS

● INDUSTRIAL PROCESS CONTROL

● FACTORY AUTOMATION

● SCADA REMOTE DATA ACQUISITION

● REMOTE TEMPERATURE AND PRESSURE

TRANSDUCERS

−200°C

Pt100 NONLINEARITY CORRECTION

USING XTR105

Process Temperature (°C)

+850°C

−1

Uncorrected

RTD Nonlinearity

Corrected

Nonlinearity

Nonlinearity (%)

DESCRIPTION

The XTR105 is a monolithic 4-20mA, 2-wire current transmit-

ter with two precision current sources. It provides complete

current excitation for platinum RTD temperature sensors and

bridges, instrumentation amplifiers, and current output cir-

cuitry on a single integrated circuit.

Versatile linearization circuitry provides a 2nd-order correc-

tion to the RTD, typically achieving a 40:1 improvement in

linearity.

Instrumentation amplifier gain can be configured for a wide

range of temperature or pressure measurements. Total un-

adjusted error of the complete current transmitter is low

enough to permit use without adjustment in many applica-

tions. This includes zero output current drift, span drift, and

nonlinearity. The XTR105 operates on loop power-supply

voltages down to 7.5V.

The XTR105 is available in DIP-14 and SO-14 surface-

mount packages and is specified for the –40°C to +85°C

industrial temperature range.

XTR105

SBOS061B – FEBRUARY 1997 – REVISED AUGUST 2004

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.

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.

All trademarks are the property of their respective owners.

Summary of content (21 pages)

PAGE 1
XTR105 XTR 105 XTR 105 SBOS061B – FEBRUARY 1997 – REVISED AUGUST 2004 4-20mA CURRENT TRANSMITTER with Sensor Excitation and Linearization FEATURES APPLICATIONS ● ● ● ● ● ● ● ● ● ● ● ● ● ● DESCRIPTION The XTR105 is a monolithic 4-20mA, 2-wire current transmitter with two precision current sources. It provides complete current excitation for platinum RTD temperature sensors and bridges, instrumentation amplifiers, and current output circuitry on a single integrated circuit.
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ABSOLUTE MAXIMUM RATINGS(1) ELECTROSTATIC DISCHARGE SENSITIVITY Power Supply, V+ (referenced to the IO pin) ...................................... 40V Input Voltage, VIN+, VIN– (referenced to the IO pin) .................... 0V to V+ Storage Temperature Range ......................................... –55°C to +125°C Lead Temperature (soldering, 10s) ............................................... +300°C Output Current Limit ................................................................
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ELECTRICAL CHARACTERISTICS At TA = +25°C, V+ = 24V, and TIP29C external transistor, unless otherwise noted. XTR105P, U PARAMETER CONDITIONS OUTPUT Output Current Equation Output Current, Specified Range Over-Scale Limit Under-Scale Limit OUTPUT(1) ZERO Initial Error vs Temperature vs Supply Voltage, V+ vs Common-Mode Voltage vs VREG Output Current Noise, 0.
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TYPICAL CHARACTERISTICS At TA = +25°C and V+ = 24V, unless otherwise noted.
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TYPICAL CHARACTERISTICS (Cont.) At TA = +25°C and V+ = 24V, unless otherwise noted.
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TYPICAL CHARACTERISTICS (Cont.) At TA = +25°C and V+ = 24V, unless otherwise noted. CURRENT SOURCE DRIFT PRODUCTION DISTRIBUTION CURRENT SOURCE MATCHING DRIFT PRODUCTION DISTRIBUTION 40 80 30 Current Source Drift (ppm/°C) Current Source Matching Drift (ppm/°C) VREG OUTPUT VOLTAGE vs VREG OUTPUT CURRENT REFERENCE CURRENT ERROR vs TEMPERATURE 30 0.02% 28 0.07% 26 12 8 10 6 4 2 75 70 60 55 50 45 40 35 30 25 20 15 0 5 0 10 10 24 20 0.
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APPLICATION INFORMATION The transfer function through the complete instrumentation amplifier and voltage-to-current converter is: Figure 1 shows the basic connection diagram for the XTR105. The loop power supply, VPS, provides power for all circuitry. Output loop current is measured as a voltage across the series load resistor, RL. IO = 4mA + VIN • (40/RG) (VIN in volts, RG in ohms) where VIN is the differential input voltage.
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MEASUREMENT TEMPERATURE SPAN ∆T (°C) TMIN 100°C 200°C 300°C 400°C 500°C 600°C 700°C 800°C 900°C 1000°C –200°C 18.7/86.6 15000 16500 18.7/169 9760 11500 18.7/255 8060 10000 18.7/340 6650 8870 18.7/422 5620 7870 18.7/511 4750 7150 18.7/590 4020 6420 18.7/665 3480 5900 18.7/750 3090 5360 18.7/845 2740 4990 –100°C 60.4/80.6 27400 29400 60.4/162 15400 17800 60.4/243 10500 13000 60.4/324 7870 10200 60.4/402 6040 8660 60.4/487 4990 7500 60.4/562 4220 6490 60.4/649 3570 5900 60.
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EXTERNAL TRANSISTOR Transistor Q1 conducts the majority of the signal-dependent 4-20mA loop current. Using an external transistor isolates the majority of the power dissipation from the precision input and reference circuitry of the XTR105, maintaining excellent accuracy. Since the external transistor is inside a feedback loop, its characteristics are not critical. Requirements are: VCEO = 45V min, β = 40 min, and PD = 800mW.
PAGE 10
In 3-wire RTD connections, an additional resistor, RLIN2, is required. As with the 2-wire RTD application, RLIN1 provides positive feedback for linearization. RLIN2 provides an offset canceling current to compensate for wiring resistance encountered in remotely located RTDs. RLIN1 and RLIN2 are chosen such that their currents are equal. This makes the voltage drop in the wiring resistance to the RTD a commonmode signal that is rejected by the XTR105.
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SAMPLE ERROR CALCULATION RTD value at 4mA Output (RRTD MIN): RTD Measurement Range: Ambient Temperature Range (∆TA): Supply Voltage Change (∆V+): Common-Mode Voltage Change (∆CM): ERROR SOURCE INPUT Input Offset Voltage vs Common-Mode Input Bias Current Input Offset Current EXCITATION Current Reference Accuracy vs Supply Current Reference Matching vs Supply 100Ω 200°C 20°C 5V 0.
PAGE 12
REVERSE-VOLTAGE PROTECTION The XTR105’s low compliance rating (7.5V) permits the use of various voltage protection methods without compromising operating range. Figure 4 shows a diode bridge circuit that allows normal operation even when the voltage connection lines are reversed. The bridge causes a two diode drop (approximately 1.4V) loss in loop-supply voltage. This results in a compliance voltage of approximately 9V—satisfactory for most applications. If a 1.
PAGE 13
12 1kΩ 13 4 RLIN1 VLIN + VIN 1 IR1 14 11 IR2 VREG 10 V+ RG RLIN2 RG B XTR105 3 E RG 9 0.01µF 8 IO 1kΩ 2 – VIN 7 IRET RZ 0.01µF 6 0.01µF RTD (1) RCM NOTE: (1) Bypass capacitors can be connected to either the IRET pin or the IO pin. 0.01µF FIGURE 5. Input Bypassing Technique with Linearization.
PAGE 14
12 13 4 1 IR1 VLIN + VIN 3 IR2 +12V 11 VREG 10 V+ 1µF RG B 9 RG 402Ω RLIN1 5760Ω 1N4148 14 XTR105 Q1 0.01µF 16 RG – VIN RTD RZ 137Ω 2 7 VO = 0 to 5V 14 13 5 4 IO = 4mA – 20mA 6 12 RCV420 IRET Pt100 100°C to 600°C 11 15 IO 2 10 3 E 8 1µF –12V RCM = 1kΩ NOTE: A 2-wire RTD connection is shown. For remotely located RTDs, a 3-wire RTD conection is recommended. RG becomes 383Ω, RLIN2 is 8060Ω. See Figure 3 and Table I. 0.01µF FIGURE 7.
PAGE 15
1.6mA 12 VLIN + 13 VIN 4 1 IR1 14 IR2 11 VREG 10 V+ RG RG XTR105 3 2 B E RG – VIN 9 8 7 IRET 6 RCM = 1kΩ(1) NOTE: (1) Use RCM to adjust the common-mode voltage to within 1.25V to 3.5V. FIGURE 9. Bridge Input, Current Excitation. XTR105 SBOS061B www.ti.
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PACKAGE OPTION ADDENDUM www.ti.
PAGE 17
PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device XTR105UA/2K5 Package Package Pins Type Drawing SOIC D 14 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 16.4 Pack Materials-Page 1 6.5 B0 (mm) K0 (mm) P1 (mm) 9.0 2.1 8.0 W Pin1 (mm) Quadrant 16.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) XTR105UA/2K5 SOIC D 14 2500 367.0 367.0 38.
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