STMicroelectronics LM334D

Overview

LM334D from STMicroelectronics is a three-terminal adjustable current source optimized for precision biasing, temperature sensing, and low-drift reference applications. It delivers programmable current from 1µA to 10mA with ±3% initial accuracy, 0.02%/V regulation, and operates across 1V–40V supply range. Its 64mV control voltage at +25°C is directly proportional to absolute temperature (°K), enabling Kelvin-referenced thermal measurement.

For engineers reviewing the LM334D datasheet, LM334D pinout, LM334D application, or LM334D equivalent, key selection criteria include its wide dynamic voltage range, temperature-proportional output, minimal external component requirement (single resistor), and SO-8 package suitability for surface-mount thermal management in sensor front-ends and analog bias networks.

Technical Context

The LM334D implements a two-transistor current mirror architecture with on-chip temperature-sensing junction, where the ADJ pin voltage (64mV @ 25°C) scales linearly with absolute temperature. This enables direct Kelvin-to-current conversion without calibration offsets.

Its current regulation relies on internal feedback that maintains constant V_ADJ across V⁺–V⁻, yielding <0.05%/V variation over 5–40V input range at 1–5mA set current. Reverse voltage tolerance up to 20V allows AC-coupled operation and rectifier-mode use.

Key Specifications

Pinout & Package

LM334D is housed in an SO-8 plastic micropackage (ECOPACK® compliant, lead-free), offering improved thermal dissipation and board-level reliability versus TO-92 variants. Pin 1 = ADJ, Pin 2 = V⁻, Pin 3 = V⁺; Pins 4–8 are NC (no connection).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM334Z, the LM334D offers superior thermal performance and surface-mount compatibility; compared with REF200, it provides full 1µA–10mA programmability at the cost of added resistor tolerance sensitivity and higher temperature coefficient.

Availability

LM334D is available at Aetrix Electronics and suitable for industrial temperature sensing, low-voltage reference drivers, and in-line current limiting applications requiring stable component supply across extended production lifecycles.

Supply support for LM334D 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The LM334D belongs to ST's precision analog current source product line, engineered specifically for Kelvin-referenced temperature measurement, micropower biasing, and programmable current regulation in harsh or space-constrained environments.

FAQ

What is the minimum operating voltage for LM334D at 10µA set current?

The LM334D requires only 0.8V across V⁺–V⁻ to operate at set currents between 2µA and 100µA. At exactly 10µA, the device functions reliably down to 0.82V, verified per Table 2 in the datasheet under "Minimum operating voltage" for the 2µA–100µA range.

Can LM334D be used as a temperature sensor without calibration?

Yes - the LM334D outputs current directly proportional to absolute temperature (I_set = 227µV/K × T / R_set). Initial gain error is typically ±3%, so one-point calibration at a known temperature (e.g., 25°C) corrects slope error to <1%, eliminating need for multi-point trimming.

Why does the LM334D have NC pins in SO-8 package?

Pins 4–8 are internally unconnected and serve mechanical and manufacturability purposes only - they provide structural symmetry for mold compound adhesion and thermal uniformity during reflow. No circuit function is assigned to these pins, and connecting them risks latch-up or parametric shift.

How does lead resistance affect LM334D accuracy at 1mA output?

A 0.7Ω contact resistance in series with the sense resistor reduces output current by 1% at 1mA because the LM334D regulates based on voltage drop across its ADJ–V⁻ terminals (<100mV). Hence, routing traces directly from ADJ and V⁻ to the resistor pads - without sockets or long leads - is mandatory for ±0.5% accuracy.