Texas Instruments XTR106U

Overview

XTR106U from Texas Instruments is a monolithic 4mA to 20mA two-wire current transmitter optimized for bridge sensor conditioning, featuring integrated 2.5V/5V bridge excitation references, 5.1V regulator output, ±25ppm/°C max span drift, and 0.25μV/°C offset drift - deployed in industrial pressure and temperature transmitters requiring high-accuracy analog signal conditioning without trimming.

For engineers reviewing the XTR106U datasheet, XTR106U pinout, XTR106U application, or XTR106U equivalent, this page delivers verified technical context, validated pin functions, confirmed linearization behavior, real-world application constraints (e.g., 1.1V–3.5V input common-mode range), and precise alternative selection guidance for field transmitter design.

Technical Context

The XTR106U implements a precision instrumentation amplifier with externally set gain (via RG pins 3–4), second-order bridge nonlinearity correction via RLIN and Lin Polarity control, and regulated current output using an external NPN transistor (B/E pins 9/8). Its transfer function is IO = 4mA + VIN × (40/RG), where VIN is differential input voltage referenced to IRET.

Linearization operates by modulating VREF (2.5V or 5V) based on input signal polarity - Lin Polarity pin (12) tied to IRET corrects positive nonlinearity; tied to VREG corrects negative nonlinearity. The device supports loop supply voltages from 7.5V to 36V and operates across –40°C to +85°C (functional to +125°C).

Key Specifications

Pinout & Package

Package: 14-pin SOIC (D package), 8.65mm × 6mm body size, surface-mount compatible, rated for –40°C to +85°C operating range.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4–20mA current transmitter applications.

Compared with XTR106PA and XTR115UA, the XTR106U offers superior bridge linearization capability, tighter drift specs, and dual-reference flexibility - making it the preferred choice for high-accuracy industrial bridge sensor transmitters where calibration-free operation is required.

Availability

XTR106U is available at Aetrix Electronics and suitable for pressure transmitters, temperature transmitters, and weighing systems requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing for industrial OEM programs.

Supply support for XTR106U includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision signal conditioning and industrial interface ICs.

The XTR106U belongs to TI's XTR series of 4–20mA current transmitters - engineered specifically for high-stability, low-drift bridge sensor signal conditioning in harsh industrial environments.

FAQ

What is the primary function of the XTR106U in a 2-wire field transmitter?

The XTR106U serves as a complete 4mA to 20mA two-wire current transmitter for bridge sensors. It integrates differential instrumentation amplification, programmable gain (via RG), 2.5V/5V bridge excitation references, 5.1V regulator output, and second-order linearization - enabling direct conversion of bridge voltage into a standardized loop current without external op-amps or discrete references. The XTR106U is designed to operate entirely from loop power.

How does the XTR106U achieve bridge nonlinearity correction, and what sensor nonlinearity can it correct?

The XTR106U corrects parabolic bridge nonlinearity by modulating the bridge excitation voltage (VREF) in proportion to the input signal using the RLIN resistor and Lin Polarity pin. With 5V excitation, it corrects up to ±5% full-scale nonlinearity; with 2.5V excitation, it handles +5%/–2.5% nonlinearity. The XTR106U requires knowledge of the sensor's nonlinearity coefficient B to calculate RLIN and adjusted RG values - achieving up to 20:1 linearity improvement over uncompensated bridges.

What is the role of the IRET pin on the XTR106U, and why must external circuitry return current through it?

The IRET pin is the local ground return for VREG, VREF2.5, and VREF5 outputs - serving as the reference node for all internal voltages and external bridge biasing. Returning external circuit current (e.g., from bridge excitation or HART modem) through IRET allows the XTR106U to include that current in its output loop calculation, preventing measurement error. If external current bypasses IRET, the XTR106U output will deviate from the true 4–20mA transfer function.

Can the XTR106U operate without an external transistor, and what are the thermal implications?

No - the XTR106U requires an external NPN transistor (e.g., TIP29C) connected to pins B (base), E (emitter), and IO (collector) to handle the majority of loop current dissipation. The XTR106U itself drives only base current; the external transistor carries the full 20mA load. This architecture isolates heat-generating elements from the precision analog core, preserving offset and gain stability. Operating without the external transistor risks thermal overload and violates absolute maximum ratings.

What are the key differences between the XTR106U and XTR106UA variants?

The XTR106U and XTR106UA share identical pinout, functionality, and package but differ in initial accuracy and drift specifications. The XTR106U has tighter offset voltage (±100µV vs. ±250µV), lower VREF drift (±35ppm/°C vs. ±75ppm/°C), and better unadjusted span error (±0.2% vs. ±0.4%). These differences reflect different test screening and binning - the XTR106U is selected for higher-precision applications such as laboratory-grade transmitters or high-reliability process control systems.