LM335AZ Precision Temperature Sensor

Overview

The LM335AZ is a precision, easily-calibrated, integrated circuit temperature sensor from the LM135 series. Operating as a 2-terminal Zener diode, the LM335AZ provides a breakdown voltage that is directly proportional to absolute temperature, with a sensitivity of +10 mV/°K. This device is designed for accurate temperature measurement and control applications, offering high linearity and stability over a wide operating range.

With a dynamic impedance of less than 1Ω, the LM335AZ operates reliably across a current range of 400 µA to 5 mA, maintaining consistent performance. When calibrated at 25°C, the sensor typically exhibits less than 1°C error over a 100°C temperature range, making it suitable for precision applications where temperature accuracy is critical.

Features

• Directly Calibrated in Kelvin: Provides an output voltage proportional to absolute temperature (+10 mV/°K).
• Wide Operating Range: Operates over a current range of 400 µA to 5 mA with minimal performance variation.
• High Accuracy: Typically less than 1°C error over a 100°C range when calibrated at 25°C.
• Low Dynamic Impedance: Less than 1Ω ensures stable operation under varying load conditions.
• Linear Output: Excellent linearity across the full temperature range.
• Easy Calibration: Simple adjustment allows for precise calibration at a known temperature.
• Low Cost: Economical solution for precision temperature sensing applications.

Applications

The LM335AZ is widely used in applications requiring accurate temperature measurement and control. Key application areas include:

• Temperature Monitoring Systems: Used in industrial, automotive, and consumer electronics for real-time temperature tracking.
• Thermal Compensation Circuits: Provides stable references for compensating temperature-sensitive components.
• HVAC Systems: Ensures precise climate control in heating, ventilation, and air conditioning units.
• Medical Equipment: Used in devices where accurate temperature measurement is critical, such as incubators and diagnostic tools.
• Battery Management: Monitors temperature in battery packs to prevent overheating and optimize charging.
• Laboratory Instruments: Provides reliable temperature data for scientific and analytical equipment.

Electrical Characteristics

The following table summarizes the key electrical specifications of the LM335AZ under typical operating conditions (unless otherwise noted):

Absolute Maximum Ratings

• Reverse Current: 5 mA (maximum)
• Forward Current: 10 mA (maximum)
• Operating Temperature Range: -40°C to +100°C
• Storage Temperature Range: -60°C to +150°C

Electrical Performance

• Output Voltage: 2.95V at 25°C (calibrated)
• Temperature Coefficient: +10 mV/°K
• Dynamic Impedance: <1Ω (typical)
• Calibration Error: ±1°C (typical over 100°C range)
• Non-Linearity: ±0.3°C (typical over full range)

Package Information

The LM335AZ is available in a TO-92 package, which is a compact and widely used through-hole package for discrete components. Key package details include:

• Package Type: TO-92 (3-pin)
• Pin Configuration:
  • Pin 1: Adjust/Calibration (optional)
  • Pin 2: V+ (positive supply/input)
  • Pin 3: V- (ground/reference)
• Dimensions: Approximately 4.95mm x 3.94mm x 4.95mm (L x W x H)
• Weight: Typically 0.35 grams
• Material: Molded plastic with metal leads

Calibration and Usage Notes

To achieve optimal performance, the LM335AZ can be calibrated at a known reference temperature (typically 25°C). A trimmer potentiometer can be connected to the adjust pin to fine-tune the output voltage for precise calibration. The following guidelines should be observed:

• Ensure the operating current remains within the specified range (400 µA to 5 mA).
• Minimize lead resistance and thermal gradients for accurate measurements.
• For high-precision applications, use a stable voltage reference for calibration.
• Avoid exposing the sensor to rapid temperature fluctuations during calibration.

Conclusion

The LM335AZ is a versatile and reliable temperature sensor, offering high accuracy, ease of calibration, and a linear output proportional to absolute temperature. Its robust performance and simple interface make it an ideal choice for a wide range of temperature sensing and control applications. Whether used in industrial systems, consumer electronics, or medical devices, the LM335AZ provides a cost-effective solution for precise thermal management.