STMicroelectronics LM335AZ

Overview

LM335AZ 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 at +25°C and operating over −40°C to +100°C. It functions as a voltage reference proportional to absolute temperature, requires only 450 µA to 5 mA bias current, and exhibits <1 Ω dynamic impedance-ideal for analog temperature monitoring in industrial control loops and environmental sensing circuits.

For engineers reviewing the LM335AZ datasheet, LM335AZ pinout, LM335AZ application, or LM335AZ equivalent, key selection criteria include its Kelvin-scaled linearity, low self-heating error under 1 mA bias, TO-92 package thermal time constant (80 s in still air), and calibration flexibility via single-point slope adjustment at 25°C.

Technical Context

The LM335AZ operates as a two-terminal shunt-mode device: cathode connects to supply, anode to ground, and ADJ pin enables external calibration. Its output voltage varies linearly with absolute temperature at precisely 10 mV/°K, with extrapolated zero at 0 K (−273.15°C). No internal amplification or digital conversion is performed-the raw Zener breakdown voltage *is* the temperature signal.

It achieves ±1°C calibrated error across −40°C to +100°C when adjusted at 25°C, with non-linearity ≤1.5°C and dynamic impedance of 0.5–0.6 Ω at 1 mA. Self-heating is minimized by operation below 1 mA, and thermal resistance junction-to-air is ~200°C/W in still air per mechanical data.

Key Specifications

Pinout & Package

LM335AZ is supplied in a TO-92 plastic package (bulk or tape-and-reel), with bottom-view pinout: Pin 1 = ADJ (calibration adjust), Pin 2 = V+ (anode/cathode common terminal), Pin 3 = V− (cathode/anode common terminal). The device uses a 2-terminal Zener configuration; ADJ is internally connected to the Zener's temperature-sensitive junction and externally accessible for fine-tuning output slope.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM335A (SO-8), LM335AZ offers field-adjustable calibration via ADJ pin but requires manual through-hole placement; compared with TS335, it delivers simpler Kelvin-linear output without scaling components-reducing BOM count and layout area for dedicated temperature measurement.

Availability

LM335AZ is available at Aetrix Electronics and suitable for industrial oven monitoring, environmental data logging, and lab equipment thermal feedback requiring stable component supply and long-term calibration consistency.

Supply support for LM335AZ 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 LM335AZ belongs to ST's precision analog temperature sensor product line, engineered specifically for applications demanding Kelvin-linear, low-drift, and field-calibratable analog temperature measurement without digital overhead.

FAQ

What is the correct bias current for optimal accuracy?

LM335AZ achieves its ±1°C calibrated accuracy specification at 1 mA bias current. Operating between 450 µA and 5 mA maintains regulation, but 1 mA balances low self-heating (0.2°C/kh drift at 125°C) and stable dynamic impedance (0.5–0.6 Ω). Lower currents increase thermal time constant; higher currents raise self-heating error.

How do I perform single-point calibration using the ADJ pin?

Apply a known reference temperature (e.g., 25°C in stirred oil bath), measure output voltage, then connect a 10 kΩ potentiometer between V+ and V− with wiper to ADJ. Adjust until output equals (273.15 + T_ref) × 10 mV-e.g., 2.982 V at 25°C. This corrects slope error across the full range without altering intercept.

Can LM335AZ be used in a 3.3 V system?

Yes-LM335AZ outputs ~2.98 V at 25°C and rises ~10 mV per °C, reaching ~3.08 V at 35°C. It operates safely up to 5 mA, so a 3.3 V supply with ≥330 Ω series resistor provides proper bias. Ensure load impedance remains >10 kΩ to avoid loading-induced error beyond specified dynamic impedance.

Why does the datasheet specify "TO-92 bottom view" for pinout?

TO-92 packages have standardized lead orientation: when viewed from the flat side (bottom), leads extend downward with Pin 1 leftmost, Pin 2 center, Pin 3 rightmost. Misidentifying top vs. bottom view causes reversed ADJ/V+/V− connections-leading to failed regulation or calibration. ST explicitly confirms this orientation in Rev 3 (2007) to prevent assembly errors.