Texas Instruments LM334SMX

Overview

LM334SMX from Texas Instruments is a 3-terminal adjustable current source optimized for 0°C to +70°C operation, delivering programmable output current from 1 μA to 10 mA with ±3% initial accuracy, 0.02%/V current regulation, and true 2-terminal operation enabled by internal floating bias. It serves as a precision current reference in LED biasing, temperature sensing, and low-power voltage references.

For engineers reviewing the LM334SMX datasheet, LM334SMX pinout, LM334SMX application, or LM334SMX equivalent, this device offers verified thermal-proportional current sourcing (≈+0.33%/°C), sub-1V minimum operating voltage at low set currents, and SOIC-8 packaging compatible with automated SMT assembly - critical for remote sensor interfaces and micropower analog signal conditioning.

Technical Context

The LM334SMX operates as a floating two-terminal current source where output current is established solely by an external resistor connected between the SET and V− terminals, with no separate power supply required. Its core function relies on a temperature-proportional 67.7 mV reference voltage (at 25°C) across the SET–V− terminals, yielding I_SET = 67.7 mV / R_SET.

It exhibits reverse voltage tolerance up to 20 V, draws only microamperes in reverse bias, and maintains stable operation over 1 V–40 V forward voltage range. The SOIC-8 package supports surface-mount reliability with θ_JA = 165°C/W and MSL Level-1 reflow compatibility.

Key Specifications

Pinout & Package

LM334SMX is housed in an 8-pin SOIC package (Package Number D), measuring 4.9 mm × 3.9 mm × 1.75 mm, with gull-wing leads and RoHS-compliant matte tin (SN) lead finish. Pin 1 is located at the top-left corner adjacent to the notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable current source applications.

Compared with LM334Z/NOPB, LM334SMX offers superior manufacturability and thermal performance in volume SMT production; compared with REF200AU, it trades fixed accuracy and dual outputs for full current programmability and wider dynamic range (1 μA–10 mA vs. fixed 100 μA), making it optimal for adaptive biasing and temperature transduction.

Availability

LM334SMX is available at Aetrix Electronics and suitable for LED driver circuits, remote temperature monitoring systems, and micropower reference designs requiring stable component supply, long-term lifecycle support, and RoHS-compliant SOIC packaging.

Supply support for LM334SMX 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 heritage in precision linear ICs and industrial-grade reliability.

The LM334 family was designed specifically for applications demanding programmable, temperature-aware current sourcing - including sensor excitation, bias networks, and self-calibrating references - with emphasis on simplicity, wide voltage range, and robustness in harsh environments.

FAQ

What is the minimum operating voltage for LM334SMX at 10 μA set current?

The LM334SMX requires a minimum forward voltage of 0.8 V when set current is ≤100 μA, as confirmed in the Electrical Characteristics table. At 10 μA, this threshold applies directly - enabling operation from weak or aging primary cells. This value increases to 1.0 V for set currents above 1 mA. The LM334SMX achieves this low headroom via its internal floating bias architecture, which eliminates dependency on external supply rails for core functionality.

Can LM334SMX be used as a temperature sensor, and what accuracy can be expected?

Yes, the LM334SMX functions as a Kelvin-proportional current source with ≈+0.33%/°C temperature coefficient, making it suitable for remote temperature sensing. While the LM234-3/LM234-6 variants are explicitly specified for ±3°C/±6°C accuracy, the LM334SMX shares identical core die characteristics and achieves comparable performance when calibrated with a single-point gain trim. Its inherent zero-offset extrapolation to 0 K simplifies calibration - slope and offset correct simultaneously - yielding <±1% slope error post-trim with proper resistor selection.

What is the purpose of the NC pins (4–8) on the LM334SMX SOIC-8 package?

Pins 4 through 8 on the LM334SMX are designated No Connect (NC) and are internally unconnected. Per Texas Instruments' package documentation and schematic diagrams, these pins must remain electrically floating - they must not be tied to ground, V+, or any other node. Their presence accommodates shared SOIC-8 footprint usage across TI's broader current-source portfolio but provides no functional role in the LM334SMX. Routing or soldering to these pins may compromise parametric performance or reliability.

How does LM334SMX achieve true 2-terminal operation despite having three active terminals?

The LM334SMX achieves true 2-terminal operation by integrating all bias circuitry internally - the SET pin senses voltage relative to V−, while current flows exclusively between V+ and V−. In standard configuration, only V+ and V− are connected to the external circuit; the SET pin is tied to V− via the programming resistor, collapsing the three-terminal topology into a functional two-terminal device. This eliminates the need for a separate power supply or ground reference, enabling seamless integration into floating or isolated signal paths.

Is LM334SMX compatible with lead-free reflow processes, and what is its MSL rating?

Yes, the LM334SMX is RoHS-compliant with matte tin (SN) lead finish and rated MSL Level-1 (unlimited floor life) per JEDEC J-STD-020. It supports peak reflow temperatures up to 260°C for 10 seconds in convection or vapor-phase ovens, fully compatible with standard lead-free soldering profiles. The SOIC-8 package (D) has been validated for both tube and tape-and-reel delivery formats, with 2500-unit reels configured for Q1 pin-1 quadrant orientation per TI's packaging specifications.