LM335Z Precision Temperature Sensor

Overview

The LM335Z is a precision integrated circuit temperature sensor that operates as a 2-terminal Zener diode. Its breakdown voltage is directly proportional to absolute temperature, with a sensitivity of +10 mV/°K. The device is part of the LM135 series, known for their accuracy, ease of calibration, and reliable performance across a wide temperature range. The LM335Z is designed for applications requiring precise temperature measurement and control, offering excellent linearity and stability.

With a dynamic impedance of less than 1Ω, the LM335Z operates effectively over 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 high-precision applications.

Features

• Directly Calibrated in Kelvin: The output voltage is linearly proportional to absolute temperature, simplifying calibration and measurement.
• Wide Operating Range: Operates over a broad current range (400 µA to 5 mA) with minimal performance variation.
• Low Dynamic Impedance: Less than 1Ω ensures stable operation under varying load conditions.
• High Accuracy: Typically less than 1°C error over a 100°C range when calibrated at 25°C.
• Easy Calibration: Can be adjusted for precise calibration using a single external potentiometer.
• Linear Output: 10 mV/°K scale factor provides straightforward interfacing with analog and digital systems.
• Low Cost: Economical solution for precision temperature sensing applications.

Applications

The LM335Z is widely used in applications requiring accurate temperature measurement and control. Its versatility and reliability make it suitable for both industrial and consumer applications.

• Temperature Measurement Systems: Used in digital thermometers, environmental monitoring, and HVAC systems.
• Industrial Control: Provides temperature feedback for process control, machinery monitoring, and automation systems.
• Consumer Electronics: Integrated into devices such as smart home systems, wearable tech, and battery management systems.
• Automotive: Monitors engine temperature, cabin climate control, and battery thermal management.
• Medical Equipment: Ensures precise temperature regulation in diagnostic devices and therapeutic systems.
• Scientific Instruments: Used in laboratory equipment for accurate temperature logging and control.

Electrical Characteristics

The following table summarizes the key electrical specifications of the LM335Z under typical operating conditions (unless otherwise noted):

• Temperature Range: -40°C to +100°C (operational)
• Output Voltage: 2.98V at 25°C (10 mV/°K scale factor)
• Calibration Accuracy: ±1°C at 25°C (after calibration)
• Operating Current: 400 µA to 5 mA
• Dynamic Impedance: <1Ω
• Line Regulation: 0.2 mV/V (typical)
• Load Regulation: 0.4 mV/mA (typical)
• Long-Term Stability: ±0.2°C/year (typical)

Absolute Maximum Ratings

• Reverse Current: 15 mA
• Forward Current: 10 mA
• Operating Temperature Range: -40°C to +100°C
• Storage Temperature Range: -60°C to +150°C

Package Information

The LM335Z is available in a TO-92 package, which is a compact and widely used through-hole package for discrete components. The package dimensions and pin configuration are as follows:

• Package Type: TO-92 (3-pin)
• Pin Configuration:
  • Pin 1: Adjust (for calibration)
  • Pin 2: V+ (positive supply/input)
  • Pin 3: V- (ground/reference)
• Dimensions:
  • Body Length: 4.95 mm (max)
  • Body Width: 3.94 mm (max)
  • Lead Spacing: 2.54 mm (standard)
• Weight: Approximately 0.35 grams

Thermal Characteristics

• Thermal Resistance (Junction-to-Air): 160°C/W (typical)
• Thermal Response Time: <10 seconds in still air

Conclusion

The LM335Z is a highly reliable and precise temperature sensor, offering excellent performance across a wide range of applications. Its linear output, ease of calibration, and robust design make it a preferred choice for engineers and designers in need of accurate temperature measurement. Whether used in industrial control systems, consumer electronics, or scientific instruments, the LM335Z delivers consistent and dependable results.