Part Number: XTR105UA

Manufacturer: Texas Instruments


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Technical Specifications of XTR105UA

Datasheet  XTR105UA datasheet
Category Integrated Circuits (ICs)
Family Interface – Sensor and Detector Interfaces
Manufacturer Texas Instruments
Packaging Tube
Part Status Active
Type Current Transmitter
Input Type Differential
Output Type Current
Interface 3-Wire
Current – Supply 20mA
Operating Temperature *
Mounting Type Surface Mount
Package / Case 14-SOIC (0.154″, 3.90mm Width)
Supplier Device Package 14-SOIC


The XTR105 is a two-wire, 4-20mA, precision current transmitter with a single chip and dual current sources. A single integrated circuit includes everything you need to excite platinum RTD temperature sensors and bridges, instrumentation amplifiers, and current output circuitry. With the aid of flexible linearization circuitry, a 40:1 improvement in linearity is typically achievable. The RTD receives a second-order correction from this circuit.

An instrumentation amplifier has a variable gain that can be set to work with a wide range of temperature and pressure readings. It is possible to use the complete current transmitter in several settings without making any adjustments because the total unadjusted error is small enough. This includes nonlinearity, zero-output-current drift, and span drift. The XTR105 can operate with loop power supply voltages as low as 7.5V.

The XTR105 is available in either a surface-mount DIP-14 or SO-14 package. It has a temperature specification of -40 degrees Celsius to +85 degrees Celsius, making it suitable for use in various industrial settings.

XTR105UA Features

  • This rtd system can run on either 2 or 3 wires.
  • Low offset drift of only 0.4 v/°C.
  • The 30napp noise level is extremely low for an output current.
  • Very loud, at least 110 dB psr.
  • Maximum SPL of 86 dB for high-CMR.
  • Supplied voltage can range from 7 to 36 volts.
  • Packages containing a dip-14 or a so-14.

XTR105UA Applications

  • Process regulation in manufacturing.
  • Mechanics of manufacturing production.
  • Using SCADA, we can gather data from afar.
  • Sensors for measuring pressure and temperature that are placed at a distance.

Application Information

The VPS loop power supply powers all electronics. The voltage across the series load resistor RL measures the output loop current. The RTD and zero-setting resistor, RZ, is powered by a pair of 0.8mA current sources that perfectly match one another. The XTR105 can detect the voltage disparity between the RTD and RZ thanks to the instrumentation amplifier input. At the low-scale (minimum) measurement temperature, RZ is set to equal the RTD’s resistance.

To compensate for the input offset voltage and reference current mismatch of the XTR105, RZ can be set to achieve 4mA output at the minimum measurement temperature. When using RCM, the inputs of the XTR105 can be biased within their common-mode input range due to the additional voltage drop provided by the component. A 0.01F capacitor can be used to bypass RCM and reduce common-mode noise.

Temperature-dependent gain adjustment of the instrumentation amplifier is accomplished via resistor RG. The RTD’s linearity can be improved by a factor of 40:1 thanks to the 2nd-order linearization correction provided by RLIN1. Using a resistor in series with a three-wire RTD connection is necessary.

External Transistor

The majority of the signal-dependent 4-20mA loop current flows through transistor Q1. Isolating the XTR105’s precision input and reference circuitry from the rest of the device’s power dissipation is essential for maintaining its high level of accuracy. An extra transistor can be used for this purpose. Because of its position within the feedback loop, the external transistor’s specific characteristics are of little relevance. The necessary conditions are as follows: Power dissipation (PD) must be 800mW, VCEO 45V, and VCEO 40. Power dissipation needs could be lessened if the loop’s power supply voltage is less than 36 volts.

The XTR105 can be operated without this external transistor, but its accuracy will suffer due to the increased power lost within the device. Running without Q1 is not advised, especially in wide temperature ranges. A 3.3 kiloohm (R) resistor connected between the IRET pin and the E (emitter) pin may be required for operation at temperatures below 0 degrees Celsius when Q1 is not present. This holds the truest near V+ = 7.5 volts.


The Pt100 RTD has been used throughout the text and figures. For RTDs with a higher resistance, it is essential to check the input voltage range and temperature tolerance to ensure the inputs are adequately biased in the standard mode. It was previously mentioned that the XTR105’s information could be biased within their common-mode input range by adjusting RCM to provide an additional voltage drop.

Reverse-Voltage Protection

The XTR105’s wide operating voltage tolerance and low compliance rating (7.5V) make it ideal for various voltage protection applications.

Surge Protection

Voltage surges are a common problem for far-flung connections to power generators. The XTR105 should be subjected to the safest possible maximum surge voltage. Many types of zener diodes and surge clamping diodes exist for this scenario. Choose a clamp diode with the lowest voltage rating possible for maximum safety. A 36V protection diode, for instance, will guarantee correct transmitter operation at typical loop voltages while providing adequate protection from voltage surges. Tests on three batches of XTR105s characterizing their resistance to loop-supply voltages up to 65V passed with flying colors.

Radio Frequency Interference

Interference from radio frequency (RF) signals is inevitable in current loops due to their long wire lengths. The sensitive XTR105 input circuitry can correct RF interference. Output current instability that shifts in response to changes in the loop supply or input wiring configuration is a common symptom of this problem. Interference may enter through the input terminals if the RTD sensor is at a distance. However, interference is more likely to originate from the current loop connections for integrated transmitter assemblies with short links to the sensor. Input bypass capacitors lessen or get rid of this type of interference. Join the IRET terminal to bypass capacitors.

The IRET terminal can be considered the transmitter’s “ground,” even though the dc voltage is not identical to 0V (at the loop supply, VPS). The 0.01uF capacitor wired between V+ and IO could reduce noise in the final product.


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