STMicroelectronics LM234Z

Overview

LM234Z from STMicroelectronics is a three-terminal adjustable current source optimized for precision biasing, temperature sensing, and low-power reference applications. It delivers programmable output current from 1 µA to 10 mA with ±3% initial accuracy, 0.02%/V input voltage regulation, and operates across 1 V to 40 V supply range. Its 64 mV control voltage at +25°C is directly proportional to absolute temperature (°K), enabling accurate remote temperature measurement in industrial sensor interfaces.

For engineers reviewing the LM234Z datasheet, LM234Z pinout, LM234Z application, or LM234Z equivalent, key selection criteria include its TO-92 package thermal behavior, 0.33%/°C inherent temperature coefficient, minimum operating voltage of 0.8 V at low set currents, and compatibility with zero-drift external compensation circuits using diodes and resistors.

Technical Context

The LM234Z functions as a two-terminal current source when configured with an external resistor between ADJ and V−, where I_set = 67.7 mV / R_set at +25°C. Its internal circuitry uses a temperature-proportional voltage reference and high-impedance current mirror to achieve wide dynamic voltage range and excellent regulation.

It supports reverse voltage tolerance up to 20 V with leakage <10 µA, enabling AC-coupled operation and rectifier-mode use. Thermal self-heating effects are significant above 100 µA-e.g., +1 V across device at 1 mA raises junction temperature by ≈0.4°C-requiring layout-aware thermal management in precision designs.

Key Specifications

Pinout & Package

LM234Z is supplied in TO-92 plastic package (Z suffix), with lead-free ECOPACK® compliance. Pinout is defined from bottom view: Pin 1 = ADJ, Pin 2 = V+, Pin 3 = V−.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM234Z, LM334Z trades industrial temperature range for lower cost in commercial settings, while REF200AU offers tighter accuracy and dual outputs but forfeits programmability and temperature-sensing capability-making LM234Z optimal for precision, adjustable, thermally aware current sourcing.

Availability

LM234Z is available at Aetrix Electronics and suitable for remote temperature sensing, precision analog biasing, and low-voltage reference driving requiring stable component supply across industrial and embedded design cycles.

Supply support for LM234Z 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The LM234Z belongs to ST's precision analog current source product line, engineered specifically for applications demanding Kelvin-proportional temperature measurement, low-power biasing, and robust current regulation across wide voltage and temperature ranges.

FAQ

What is the correct pinout orientation for LM234Z in TO-92 package?

The LM234Z TO-92 pinout is defined from the bottom view: Pin 1 (left) is ADJ, Pin 2 (center) is V+, and Pin 3 (right) is V−. This matches the official STMicroelectronics mechanical drawing and differs from top-view conventions-incorrect orientation causes regulation failure or excessive heating.

Can LM234Z be used as a true 2-terminal current source?

Yes-by connecting the ADJ pin directly to V−, the LM234Z functions as a 2-terminal device where current flows from V+ to V−. The set current is then determined solely by the external resistor between ADJ and V−, eliminating need for separate reference connections in simple biasing applications.

How does thermal self-heating affect LM234Z accuracy at 1 mA?

At 1 mA and +1 V across the device, self-heating raises junction temperature by ≈0.4°C in still air. Since I_set has a 0.33%/°C coefficient, this induces ~0.13% current drift-degrading regulation by 10:1 versus intrinsic electrical performance. Layout with thermal relief or reduced voltage drop mitigates this effect.

What resistor tolerance and TCR are required for ±0.5% total current accuracy?

To achieve ±0.5% total I_set accuracy, the external R_set must have ≤0.1% initial tolerance and ≤20 ppm/°C TCR. A 33 ppm/°C resistor introduces ~1% slope error over temperature due to matched drift with the LM234Z's own 0.33%/°C coefficient-metal-film or precision wirewound types are recommended.