SNIS153D July   2009  – October 2015 LM75B


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Temperature-to-Digital Converter Characteristics
    6. 6.6 Digital DC Characteristics
    7. 6.7 I2C Digital Switching Characteristics
    8. 6.8 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Digital Temperature Sensor
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 I2C Bus Interface
      2. 7.5.2 Temperature Data Format
      3. 7.5.3 Shutdown Mode
      4. 7.5.4 Fault Queue
      5. 7.5.5 Comparator and Interrupt Mode
      6. 7.5.6 O.S. Output
      7. 7.5.7 O.S. Polarity
      8. 7.5.8 Internal Register Structure
    6. 7.6 Register Maps
      1. 7.6.1 Pointer Register (Selects Which Registers Will Be Read From or Written to):
      2. 7.6.2 Temperature Register (Read Only):
      3. 7.6.3 Configuration Register (Read/Write):
      4. 7.6.4 THYST and TOS Register (Read/Write):
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Simple Fan Controller, Interface Optional
        1. Design Requirements
        2. Detailed Design Procedure
        3. Application Curve
    3. 8.3 System Examples
      1. 8.3.1 Simple Thermostat, Interface Optional
      2. 8.3.2 Temperature Sensor with Loudmouth Alarm (Barking Watchdog)
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Digital Noise Issues
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Related Links
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8 Application and Implementation


Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The wide temperature and supply range and I2C interface make the LM75 ideal for a number of applications including base stations, electronic test equipment, office electronics, personal computers, and any other system where thermal management is critical to performance.

8.2 Typical Application

8.2.1 Simple Fan Controller, Interface Optional

LM75B LM75C 30099812.gif
When using the two-wire interface: program O.S. for active high and connect O.S. directly to Q2's gate.
Figure 12. Simple Fan Controller, Interface Optional Design Requirements

The LM75 requires a positive supply voltage of 2.7 V to 5.5 V to be applied between +Vs and GND. For best results, bypass capacitors of 100 nF and 10 µF are recommended. Pull-up resistors of 10 kΩ are required on SCL and SDA. Detailed Design Procedure

Accessing the conversion result of the LM75 consists of writing an address byte followed by retrieving the corresponding number of data bytes. The first data byte is the most significant byte with the most significant bit first, permitting only as much data as necessary to be read to determine temperature condition. For instance, if the first four bits of the temperature data indicates an overtemperature condition, the host processor could immediately take action to remedy the excessive temperatures. At the end of a read, the LM75 can accept either Acknowledge or No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave that the Master has read its last byte). Temperature data is two's complement format and one LSB is equivalent to 0.5°C. Application Curve

LM75B LM75C 30099818.png Figure 13. Temperature Accuracy

8.3 System Examples

8.3.1 Simple Thermostat, Interface Optional

LM75B LM75C 30099814.gif Figure 14. Simple Thermostat, Interface Optional

8.3.2 Temperature Sensor with Loudmouth Alarm (Barking Watchdog)

LM75B LM75C 30099815.gif Figure 15. Temperature Sensor with Loudmouth Alarm (Barking Watchdog)