NXP LM75AD,118 Digital Temperature Sensor: Datasheet, Pinout, and Application Circuit Guide
The NXP LM75AD,118 is a highly integrated digital temperature sensor renowned for its precision, ease of use, and robust feature set. It converts temperature directly into a digital form, communicating with a host controller via the ubiquitous I²C-bus interface. This guide provides a detailed overview of its datasheet, pin configuration, and a typical application circuit to streamline your design process.
Datasheet Overview and Key Features
The LM75AD,118 datasheet details a sensor that operates as a stand-alone thermostat with programmable hysteresis and overtemperature shutdown. Its key specifications include:
Temperature Range: -55°C to +125°C
Accuracy: ±2°C from -25°C to +100°C
Resolution: 0.125°C (11-bit ADC)
Supply Voltage: 2.8 V to 5.5 V, making it suitable for both 3.3V and 5V systems.
Low Power Consumption: Typically 3.5 µA in shutdown mode, ideal for battery-powered applications.
Programmable Alert Output (OS): This open-drain output activates when the temperature exceeds a user-programmed limit. It can operate in either comparator or interrupt mode, providing flexibility for system control.
I²C Address Selection: Three address pins (A0-A2) allow up to eight devices to be connected on the same bus, facilitating multi-zone temperature monitoring.
Pinout Configuration
The LM75AD,118 is available in an 8-pin SOIC package. Its pinout is as follows:
1. SDA (Serial Data): Bi-directional data line for the I²C bus.
2. SCL (Serial Clock): Clock input for the I²C bus.
3. OS: Overtemperature Shutdown output (active-low, open-drain).
4. GND: Ground connection.
5. A0, A1, A2: Address input pins for setting the device's I²C slave address.
6. VCC: Positive supply voltage (2.8V to 5.5V).
7. NC: No internal connection.
Typical Application Circuit Guide
A fundamental application circuit for the LM75AD,118 is straightforward, requiring minimal external components. Below is a guide for a standard setup:
1. Power Supply Decoupling: Place a 100nF ceramic decoupling capacitor close to the VCC and GND pins to filter high-frequency noise.
2. I²C Bus Pull-up Resistors: Both the SDA and SCL lines require pull-up resistors to VCC. Typical values range from 2.2 kΩ to 10 kΩ, depending on the bus speed and capacitance.
3. OS Output Handling: The OS output is open-drain and requires an external pull-up resistor to a logic voltage level. This pull-up voltage can be the same as VCC or a different voltage, provided it does not exceed the absolute maximum rating. A 10 kΩ resistor is a common value.
4. Address Configuration: Connect the A0, A1, and A2 pins either to GND (logic 0) or VCC (logic 1) to set the desired 7-bit I²C slave address (1001A2A1A0).
A simple circuit diagram would show the microcontroller's I²C lines connected to the sensor's SDA and SCL, with the OS line connected to a microcontroller interrupt or GPIO pin for alert monitoring.
ICGOODFIND Summary
The NXP LM75AD,118 stands out as an exceptionally versatile and reliable solution for digital temperature sensing. Its combination of high accuracy, a wide operating voltage range, programmable alarm functionality, and simple I²C interface makes it an excellent choice for a vast array of applications, including system thermal management, industrial control systems, and consumer electronics. Its minimal external component requirement allows for quick integration and a compact design footprint.
Keywords: Digital Temperature Sensor, I²C Interface, Programmable Hysteresis, Overtemperature Shutdown, Thermal Management
