STMicroelectronics LM335D

Overview

LM335D 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 <1 Ω dynamic impedance, and is housed in an SO-8 plastic micropackage. It serves as a direct-replacement analog temperature transducer in industrial monitoring and embedded thermal control circuits.

For engineers reviewing the LM335D datasheet, LM335D pinout, LM335D application, or LM335D equivalent, key selection criteria include its absolute-temperature linearity, low self-heating error at 1 mA bias, TO-92/SO-8 package compatibility, and calibration stability across extended temperature ranges without external compensation circuitry.

Technical Context

The LM335D 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 reference voltage or excitation current regulation.

It achieves <0.3°C non-linearity (typ.) and ±1°C calibrated error over –40°C to +100°C when biased at 1 mA. Thermal time constant is 10 s in air at 0.5 m/s and 1 s in stirred oil-critical for response-limited thermal feedback loops.

Key Specifications

Pinout & Package

LM335D is supplied in an SO-8 plastic micropackage (JEDEC MS-012AC), with 8-pin configuration and exposed pad not electrically connected. Pin 1 is marked by notch or dot; pin numbering follows standard SO-8 top-view convention.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar precision analog temperature sensing applications.

Compared with LM335AZ and TSYS01, the LM335D offers optimal trade-off between analog simplicity and surface-mount manufacturability-retaining the LM335 family's proven 10 mV/°K transfer function while enabling automated assembly and improved thermal response over TO-92 variants.

Availability

LM335D is available at Aetrix Electronics and suitable for industrial oven monitoring, embedded HVAC sensor nodes, differential temperature sensing, and thermocouple cold-junction compensation requiring stable component supply and long-term production continuity.

Supply support for LM335D 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 LM335 series belongs to ST's precision analog temperature sensor product line, engineered specifically for applications demanding direct Kelvin output, minimal external components, and robust performance across commercial and industrial temperature ranges.

FAQ

What is the recommended operating current for LM335D to minimize self-heating error?

The LM335D achieves optimal accuracy at 1 mA bias current, yielding <0.2°C self-heating error in still air. At 450 µA, self-heating drops below 0.1°C but output noise increases; above 2 mA, thermal drift rises nonlinearly. ST specifies 450 µA–5 mA as safe operating range, but 0.8–1.2 mA is preferred for metrology-grade applications.

Can LM335D be used without calibration in a 0–100°C measurement system?

Yes-LM335D delivers ±1°C initial accuracy at +25°C and ±2°C max error over –40°C to +100°C without calibration. For 0–100°C use, output spans 273.15 mV to 373.15 mV (10 mV/°K); a simple 273.15 mV offset subtraction in firmware yields Celsius directly. Calibration improves accuracy to ±0.5°C but is optional for non-critical monitoring.

How does the ADJ pin function in LM335D, and what external components are needed?

The ADJ pin enables single-point slope calibration: a 10 kΩ potentiometer between V+ and V–, with wiper connected to ADJ, adjusts output gain. At +25°C (298.15 K), adjust until output = 2.9815 V. This corrects batch-to-batch sensitivity variation while preserving 10 mV/°K linearity. No capacitors or op-amps are required-only the potentiometer and stable reference temperature bath or ice point.

Is LM335D compatible with 3.3 V microcontroller ADC inputs?

Yes-LM335D output at +100°C is 373.15 mV, well within 0–3.3 V ADC range. For full-scale utilization, use a 10× non-inverting op-amp stage or configure ADC reference to 1.1 V internal bandgap. Direct connection works for coarse readings; gain staging improves resolution to ~0.1°C per LSB with 12-bit ADC. Avoid exceeding 5 mA total current draw from MCU GPIO if used as bias source.