STMicroelectronics LM335DT

Overview

LM335DT from STMicroelectronics is a precision 2-terminal Zener-based temperature sensor calibrated in Kelvin, delivering 10 mV/°K linear output with ±1°C initial accuracy over −40°C to +100°C. It operates from 450 µA to 5 mA, exhibits <0.6 Ω dynamic impedance, and is housed in an SO-8 plastic micropackage for surface-mount thermal sensing applications in industrial control systems.

For engineers reviewing the LM335DT datasheet, LM335DT pinout, LM335DT application, or LM335DT equivalent, key selection criteria include its Kelvin-referenced linearity, low self-heating error at 1 mA bias, SO-8 thermal time constant of 10 s in moving air, and compatibility with single-point slope calibration for system-level accuracy correction.

Technical Context

The LM335DT functions as a programmable Zener diode whose breakdown voltage tracks absolute temperature at 10 mV/°K, enabling direct Kelvin-to-voltage conversion without signal conditioning. Its two-terminal architecture eliminates need for external reference or op-amp circuitry.

It achieves calibrated error ≤1°C across −40°C to +100°C when adjusted at 25°C, with non-linearity ≤1.5°C and output voltage drift stability of ±10 mV/°C. Thermal resistance and time constant are specified for SO-8 package in still air (80 s) and 0.5 m/s airflow (10 s).

Key Specifications

Pinout & Package

LM335DT uses an SO-8 plastic micropackage (JEDEC MS-012AC), with 8-pin configuration and gull-wing leads. Pin 1 is marked by notch or dot; device orientation follows standard top-view layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar precision Kelvin-referenced temperature sensing applications.

Compared with LM335Z and TSYS01, the LM335DT offers optimal balance of analog simplicity, SO-8 manufacturability, and thermal responsiveness - ideal for cost-sensitive, high-volume SMT thermal monitoring where Kelvin linearity and minimal BOM count are prioritized.

Availability

LM335DT is available at Aetrix Electronics and suitable for industrial process monitoring, environmental data logging, thermocouple cold-junction compensation, and embedded HVAC control requiring stable component supply across production lifecycles.

Supply support for LM335DT 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 LM335DT belongs to ST's precision analog temperature sensor family, engineered specifically for Kelvin-linear, low-drift thermal measurement in space-constrained SMT applications where calibration simplicity and long-term stability are critical.

FAQ

What is the correct biasing method for LM335DT to ensure ±1°C accuracy?

Apply a constant current source between 1 mA and 2 mA using a series resistor from V+ to V−, sized per supply voltage (e.g., 3.3 kΩ for 5 V). Avoid voltage biasing - current regulation minimizes self-heating error and maintains specified dynamic impedance. Calibration at 25°C adjusts ADJ pin to set 2.982 V output.

Can LM335DT be used below −40°C or above +100°C?

No - the LM335DT is rated for −40°C to +100°C operation only. Beyond this range, output drift exceeds specification limits and thermal stress risks permanent parametric shift. For extended ranges, ST recommends LM135Z (−55°C to +150°C) in TO-92 package, which shares identical electrical behavior but different thermal envelope.

Why does the SO-8 pinout show multiple NC pins, and how should they be handled on PCB?

The SO-8 package contains five NC pins (2, 4, 5, 7, 8) due to die pad layout constraints and internal isolation requirements. These pins must remain unconnected - no traces, vias, or copper pours. PCB layout must avoid solder mask openings or thermal reliefs on NC pads to prevent unintended leakage paths or mechanical stress.

How does self-heating affect LM335DT accuracy, and how is it quantified?

At 1 mA bias, self-heating raises junction temperature by ~0.2°C in still air, contributing directly to measurement error. ST specifies "uncalibrated temperature error" (up to ±5°C) inclusive of self-heating; calibrated error (±1°C) assumes proper thermal mounting and airflow. Use lower bias current (450 µA) in sealed enclosures to reduce self-heating to <0.1°C.