Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsLinear ICsXTR101AU

FEATURES

D INSTRUMENTATION AMPLIFIER INPUT:

− Low Offset Voltage, 30µV max

− Low Voltage Drift, 0.75µV/°C max

− Low Nonlinearity, 0.01% max

D TRUE TWO-WIRE OPERATION:

− Power and Signal on One Wire Pair

− Current Mode Signal Transmission

− High Noise Immunity

D DUAL MATCHED CURRENT SOURCES

D WIDE SUPPLY RANGE: 11.6V to 40V

D SPECIFICATION RANGE: −40°C to +85°C

D SMALL DIP-14 PACKAGE, CERAMIC AND

PLASTIC

APPLICATIONS

D INDUSTRIAL PROCESS CONTROL:

− Pressure Transmitters

− Temperature Transmitters

− Millivolt Transmitters

D RESISTANCE BRIDGE INPUTS

D THERMOCOUPLE INPUTS

D RTD INPUTS

D CURRENT SHUNT (mV) INPUTS

D PRECISION DUAL CURRENT SOURCES

D AUTOMATED MANUFACTURING

D POWER/PLANT ENERGY SYSTEM

MONITORING

DESCRIPTION

The XTR101 is a microcircuit, 4-20mA, two-wire

transmitter containing a high accuracy instrumentation

amplifier (IA), a voltage-controlled output current source,

and dual-matched precision current reference. This

combination is ideally suited for remote signal conditioning

of a wide variety of transducers such as thermocouples,

RTDs, thermistors, and strain gauge bridges. State-of-the-

art design and laser-trimming, wide temperature range

operation, and small size make it very suitable for

industrial process control applications. In addition, the

optional external transistor allows even higher precision.

The two-wire transmitter allows signal and power to be

supplied on a single wire pair by modulating the

power-supply current with the input signal source. The

transmitter is immune to voltage drops from long runs and

noise from motors, relays, actuators, switches,

transformers, and industrial equipment. It can be used by

OEMs producing transmitter modules or by data

acquisition system manufacturers.

XTR101

(1)

Optional

Offset Null

Optional

External

Transistor

REF1

REF2

OUT

(1)

Span

NOTE: (1) Pins 12 and 13 are used for optional BW control.

−

XTR101

SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004

Precision, Low Drift

4-20mA TWO-WIRE TRANSMITTER

         

          

 !     !   

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Summary of content (25 pages)

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XTR101 SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 Precision, Low Drift 4-20mA TWO-WIRE TRANSMITTER FEATURES D INSTRUMENTATION AMPLIFIER INPUT: − Low Offset Voltage, 30µV max − Low Voltage Drift, 0.75µV/°C max − Low Nonlinearity, 0.01% max D TRUE TWO-WIRE OPERATION: − Power and Signal on One Wire Pair − Current Mode Signal Transmission − High Noise Immunity D D D D DUAL MATCHED CURRENT SOURCES WIDE SUPPLY RANGE: 11.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 ABSOLUTE MAXIMUM RATINGS(1) Power Supply, +VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40V Input Voltage, e1 or e2 . . . . . . . . . . . . . . . . . . . . ≥ VOUT, ≤ +VCC Storage Temperature Range, Ceramic . . . . . . . . . −55°C to +165°C Plastic . . . . . . . . . . −55°C to +125°C Lead Temperature (soldering, 10s) G, P . . . . . . . . . . . . . . . +300°C (wave soldering, 3s) U . . . . . . . . . . . . . .
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 ELECTRICAL CHARACTERISTICS At TA = +25°C, +VCC = 24VDC, and RL = 100Ω with external transistor connected, unless otherwise noted.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 TYPICAL CHARACTERISTICS At TA = +25°C and VCC = 24VDC, unless otherwise noted.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VDD = +3.3V, and VIO = +3.3V, unless otherwise noted.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 THEORY OF OPERATION A simplified schematic of the XTR101 is shown in Figure 1. Basically, the amplifiers A1 and A2 act as a single power-supply instrumentation amplifier controlling a current source, A3 and Q1. Operation is determined by an internal feedback loop. e1 applied to pin 3 will also appear at pin 5, and similarly, e2 will appear at pin 6. Therefore, the current in RS (the span setting resistor) will be IS = (e2 − e1)/RS = eIN/RS.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 OPTIONAL EXTERNAL TRANSISTOR INSTALLATION AND OPERATING INSTRUCTIONS The optional external transistor, when used, is connected in parallel with the XTR101 internal transistor. The purpose is to increase accuracy by reducing heat change inside the XTR101 package as the output current spans from 4-20mA. Under normal operating conditions, the internal transistor is never completely turned off, as shown in Figure 2.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 Although any NPN of suitable power rating will operate with the XTR101, two readily available transistors are recommended: 1. 2N2222 in the TO-18 package. For power-supply voltages above 24V, a 750Ω, 1/2W resistor should be connected in series with the collector. This will limit the power dissipation to 377mW under the worst-case conditions; see Figure 2.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 SELECTING THE RS 11 10 e1 3 − RSPAN is chosen so that a given full-scale input span (eINFS) will result in the desired full-scale output span of ∆IOFS: ƪǒ Ǔ ǒ Ǔƫ De amps 0.016 ) 40 volt RS 5 − IN 2mA + DI O + 16mA. eIN RS Adj. + 6 Solving for RS: 4−20mA XTR101 e2 + 4 RS + 40 amps DI OńDe IN * 0.016 volt + (1) +4V ≤ e2 ≤ +6V The offset adjustment is used to remove the offset voltage of the input amplifier.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 SIGNAL SUPPRESSION AND ELEVATION In some applications, it is desired to have suppressed zero range (input signal elevation) or elevated zero range (input signal suppression). This is easily accomplished with the XTR101 by using the current sources to create the suppression/elevation voltage. The basic concept is shown in Figure 7 and Figure 8(a).
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 EXAMPLE 1 e1 An RTD transducer is shown in Figure 9. 3 Given a process with temperature limits of +25°C and +150°C, configure the XTR101 to measure the temperature with a platinum RTD which produces 100Ω at 0°C and 200Ω at +266°C (obtained from standard RTD tables). Transmit 4mA for +25°C and 20mA for +150°C. COMPUTING RS: The sensitivity of the RTD is ∆R/∆T = 100Ω/266°C.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 ESTABLISHING RS: R5 is chosen as 2kΩ to be much larger than the resistance of the diode. Solving for R6 yields 51Ω. The input full-scale span is 58mV (∆eINFS = 58mV). RS is found from Equation 1. 40 amps DI OńDe IN * 0.016 volt 40 + + 40 + 153.9W 0.2599 16mAń58mV * 0.016AńV RS + SELECTING R4: R4 is chosen to make the output 4mA at TTC = 0°C (VTC = −1.28mV) and TD = +25°C (VD = 0.6V); see Figure 10.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 OPTIONAL BANDWIDTH CONTROL f CO + 0.0047µF 1mA Low-pass filtering is recommended where possible and can be done by either one of two techniques; see Figure 12. C2 connected to pins 3 and 4 will reduce the bandwidth with a cutoff frequency given by: R3(1) 3 11 − 1mA 15.9 (R1 ) R2 ) R3 ) R 4)(C2 ) 3pF) C2 XTR101 R1 This method has the disadvantage of having fCO vary with R1, R2, R3, R4, and it may require large values of R3 and R4.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 0.9852mA 2mA 1.0147mA 1.8kΩ R R LM129 6.9V Voltage Ref − 300Ω R RS XTR101 R + 4.7kΩ 0.01µF Figure 14. Bridge Input, Voltage Excitation 1mA 2mA R R − 300Ω − Type J − + R R 51Ω RS RS 20Ω XTR101 This circuit has downscale burn−out indication. 1mA 2kΩ XTR101 J 2.2kΩ 2.5kΩ Figure 15. Bridge Input, Current Excitiation 1mA 15Ω RTD 100Ω This circuit has upscale burn−out indication.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 11 I1 I2 10 +VCC 8 +VCC − 3 OPA21 15V 0.01µF R1 XTR101 7 + VREF Out R2 4 2.5kΩ VREF = ImA R2 Figure 19.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 DETAILED ERROR ANALYSIS EXAMPLE 3 The ideal output current is: See the circuit in Figure 9 with the XTR101BG specifications and the following conditions: RT = 109.4Ω at 25°C, RT = 156.4Ω at 150°C, IO = 4mA at 25°C, IO = 20mA at 150°C, RS = 123.3Ω, R4 = 109Ω, RL = 250Ω, RLINE = 100Ω, VDI = 0.6V, and VPS = 24V ± 0.5%. Determine the % error at the upper and lower range values.
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" #$# www.ti.com SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004 B. AT THE UPPER RANGE VALUE (T = +150°C) DR + R T 150oC * R 4 + 156.4 * 109.4 + 47W DV CC + ǒ24 0.005Ǔ ) 20mAǒ250W ) 100WǓ ) 0.6V + 7720mV e 1 + 5.109V e 2 + ǒ2mA 2.5kWǓ ) ǒ1mA + 5.156V ǒe 1 * e 2Ǔ 2 156.4WǓ * 5V + 0.1325V s O + 6mA s 1 + 30mV ) ǒ150nA 47W ) 20nA 190WǓ ) 7720mV ) 0.1325V 3.16 105 3.16 10 3 + 30mV ) 9.23mV ) 24mV ) 4.19mV + 67.42mV s S + 0.0001 e IN + eȀ 2 * V 4 + IREF1 R T 150oC * IREF2 R 4 + ǒ1mA + 47mV 156.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 4-Jun-2012 Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device XTR101AU/1K Package Package Pins Type Drawing SOIC DW 16 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 1000 330.0 16.4 Pack Materials-Page 1 10.75 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 10.7 2.7 12.0 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) XTR101AU/1K SOIC DW 16 1000 367.0 367.0 38.
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