STMicroelectronics LM135Z

Overview

LM135Z 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 –55°C to +150°C, <1 Ω dynamic impedance, and operation from 450 µA to 5 mA - used for high-stability thermal monitoring in industrial control and environmental sensing systems.

For engineers reviewing the LM135Z datasheet, LM135Z pinout, LM135Z application, or LM135Z equivalent, key selection criteria include absolute temperature linearity, self-heating mitigation at low bias current, TO-92 thermal time constant in still air (80 s), and calibration flexibility via single-point slope adjustment at 25°C.

Technical Context

The LM135Z functions as a temperature-dependent Zener diode with output voltage directly proportional to absolute temperature (10 mV/°K nominal), requiring no external components for basic operation. Its two-terminal architecture simplifies PCB layout while maintaining tight thermal tracking due to low dynamic impedance (0.5–0.6 Ω) and minimal non-linearity (≤0.3°C).

Calibration relies on slope correction only - since extrapolated zero occurs at 0 K (–273.15°C), a single-point adjustment at 25°C (298.15 K → 2.982 V) corrects full-range error. It operates across 450 µA–5 mA reverse current without parameter shift, enabling compatibility with both low-power and noise-immune biasing schemes.

Key Specifications

Pinout & Package

LM135Z is supplied in TO-92 plastic package (bulk packing), with three leads arranged in bottom-view orientation: Pin 1 = Adjust (ADJ), Pin 2 = Positive Terminal (V+), Pin 3 = Negative Terminal (V–). The device operates as a 2-terminal device; ADJ is unused in standard configurations but enables fine calibration when connected externally.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM335Z and TSIC 506, the LM135Z uniquely balances wide temperature range (–55°C to +150°C), analog simplicity, and ±1°C factory accuracy - making it optimal for ruggedized analog systems where digital interfaces are impractical or EMI-sensitive.

Availability

LM135Z is available at Aetrix Electronics and suitable for industrial oven monitoring, motor winding thermal protection, and environmental data logging requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for LM135Z 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, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The LM135Z belongs to ST's precision analog temperature sensor family, engineered specifically for applications demanding Kelvin-linear output, minimal self-heating, and robust operation across extreme ambient temperatures without digital overhead.

FAQ

What is the correct biasing method for LM135Z to minimize self-heating error?

Apply a constant reverse current between 450 µA and 1 mA using a series resistor from a stable voltage rail. At 1 mA, self-heating is typically <0.2°C in still air; lower currents further reduce thermal offset but increase susceptibility to noise. Avoid exceeding 5 mA unless thermal mass is sufficient to dissipate 15 mW continuously.

Can LM135Z be used without calibration in a system requiring ±2°C accuracy?

Yes - the LM135Z has ±1°C initial accuracy at +25°C and maintains ≤2°C error over its full –55°C to +150°C range when operated at 1 mA. No calibration is needed for applications like motor overtemperature alarms or HVAC ambient monitoring where ±2°C meets specification.

How does the ADJ pin function, and when should it be used?

The ADJ pin enables external slope trimming via a resistor divider between V+ and V–. It is unused in standard configurations. Use only when compensating for batch-level sensitivity deviation (e.g., adjusting from 9.95 mV/°K to 10.00 mV/°K); connect ADJ to V– through a 10 kΩ potentiometer for field calibration.

Is LM135Z compatible with PCB reflow soldering processes?

Yes - the TO-92 package is rated for standard lead-free reflow profiles per JEDEC J-STD-020. Peak temperature must not exceed 260°C for ≤10 seconds. ST specifies moisture sensitivity level (MSL) as MSL-1 (unlimited floor life), and the ECOPACK® marking confirms RoHS-compliant second-level interconnect.