Texas Instruments XTR116U

Overview

XTR116U from Texas Instruments is a precision 4–20 mA current-loop transmitter IC designed for industrial sensor signal conditioning and loop-powered field transmitters. It features a 4.096 V on-chip reference, 5 V regulator, 100× current gain, ±0.05% span error, and operates from 7.5 V to 36 V loop supply across –40°C to +85°C. It drives external NPN transistors for high-current output in two-wire transmitter designs.

For engineers reviewing the XTR116U datasheet, XTR116U pinout, XTR116U application, or XTR116U equivalent, key selection considerations include its 4.096 V VREF for ratiometric bridge excitation, IRET-sensed local ground return for accurate current summation, low 200 µA quiescent current enabling sub-4 mA operation, and compatibility with HART modulation in process control loops.

Technical Context

The XTR116U implements a precision current-input architecture where input current (IIN) at Pin 2 is amplified by a fixed 100× transconductance stage to produce regulated 4–20 mA loop output (IO) at Pin 4. Its internal 4.096 V reference (Pin 1) and 5 V regulator (Pin 8) are referenced to IRET (Pin 3), enforcing strict local ground return for all external circuitry powered by those rails.

It requires an external NPN transistor (e.g., TIP29C) connected between Pins 5 (E) and 6 (B) to handle full-scale loop current, isolating thermal effects from the precision core. The device operates in a single functional mode within 7.5–36 V supply and –40°C to +85°C ambient, with absolute maximum V+ of 40 V and junction temperature limit of 165°C.

Key Specifications

Pinout & Package

Package: SOIC-8 (D), 4.90 mm × 3.90 mm, surface-mount, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XTR116U, the XTR116UA/2K5 offers enhanced reference stability for metrology-critical use, while the XTR117 removes VREF to reduce cost and complexity in non-ratiometric applications-neither is pin-compatible with XTR116U in reference-dependent circuits.

Availability

XTR116U is available at Aetrix Electronics and suitable for field transmitter & sensor, flow transmitter, and temperature transmitter applications requiring stable component supply, long-term industrial lifecycle support, and consistent parametric performance across manufacturing lots.

Supply support for XTR116U 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 solutions.

The XTR116U belongs to TI's XTR current-loop transmitter product line, engineered specifically for robust, low-power, two-wire 4–20 mA field instrumentation in harsh industrial environments.

FAQ

What is the reference voltage output of the XTR116U?

The XTR116U provides a precision 4.096 V reference voltage at Pin 1 (VREF), specified with ±0.1% initial accuracy and ±35 ppm/°C temperature coefficient over –40°C to +85°C. This voltage is referenced to IRET (Pin 3) and supports up to 2.5 mA load current. It is distinct from the XTR115's 2.5 V reference and is optimized for 12-bit ratiometric sensor interfaces. The XTR116U's VREF is a core differentiator enabling high-resolution bridge excitation without external references.

Does the XTR116U require an external transistor?

Yes, the XTR116U requires an external NPN transistor (e.g., TIP29C, FCX690BTA) connected between Pins 5 (E) and 6 (B) to handle full-scale 20 mA loop current. The IC drives the transistor's base but does not integrate the high-current pass element. This architecture minimizes on-die self-heating, preserving accuracy. Operating the XTR116U without an external transistor is possible only at very low currents (<2 mA) and is not recommended for standard 4–20 mA applications due to thermal error risks.

How does the IRET pin function in the XTR116U?

The IRET pin (Pin 3) serves as the local ground return for all current sourced from VREG (Pin 8) and VREF (Pin 1). Any current drawn from those outputs must return through IRET to ensure accurate summation into the output current IO (Pin 4). This design prevents ground-loop errors and maintains precision even when external circuitry (e.g., op-amps, ADCs) shares the same local power domain. Failure to route all VREG/VREF return current through IRET degrades span accuracy beyond ±0.05%.

Can the XTR116U support HART communication?

Yes, the XTR116U supports HART communication because its output stage has sufficient bandwidth (>380 kHz small-signal bandwidth) and low output impedance to superimpose the 1200/2200 Hz FSK HART signal onto the 4–20 mA DC loop current without distortion. To maintain signal integrity, TI recommends using a 2–3 nF bypass capacitor between V+ and IO instead of the standard 10 nF for non-HART applications. The XTR116U's architecture inherently meets HART physical layer requirements when paired with a compliant modem.

What is the minimum loop supply voltage for the XTR116U?

The XTR116U requires a minimum loop supply voltage of 7.5 V at Pin 7 (V+) to maintain full 4–20 mA output compliance across temperature and process variations. At 24 V nominal supply, it supports up to 1 kΩ loop load (per Ohm's Law: 20 mA × 1 kΩ = 20 V drop). Below 7.5 V, the device cannot regulate output current accurately and may enter dropout; absolute maximum V+ is 40 V to prevent permanent damage. The 7.5 V minimum enables reliable operation even with significant line loss in long cable runs.