SNIS139F February   2005  – January 2024 LM95231

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 Operating Ratings
    3. 5.3 Temperature-to-Digital Converter Characteristics
    4. 5.4 Logic Electrical Characteristics Digital DC Characteristics
    5. 5.5 Logic Electrical Characteristics SMBus Digital Switching Characteristics
    6. 5.6 Typical Performance Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Conversion Sequence
      2. 6.3.2 Power-On-Default States
      3. 6.3.3 SMBus Interface
      4. 6.3.4 Temperature Data Format
      5. 6.3.5 SMBDAT Open-Drain Output
      6. 6.3.6 Diode Fault Detection
      7. 6.3.7 Communicating with the LM95231
      8. 6.3.8 Serial Interface Reset
      9. 6.3.9 One-Shot Conversion
  8. 7 Registers
    1. 7.1 LM95231 Registers
    2. 7.2 Status Register
    3. 7.3 Configuration Register
    4. 7.4 Remote Diode Filter Control Register
    5. 7.5 Remote Diode Model Type Select Register
    6. 7.6 Remote TruTherm Mode Control
    7. 7.7 Local and Remote MSB and LSB Temperature Registers
      1. 7.7.1 Local Temperature MSB
      2. 7.7.2 Local Temperature LSB
      3. 7.7.3 Remote Temperature MSB
      4. 7.7.4 Remote Temperature LSB
    8. 7.8 Manufacturers ID Register
    9. 7.9 Die Revision Code Register
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Diode Non-Ideality
        1. 8.2.1.1 Diode Non-Ideality Factor Effect on Accuracy
        2. 8.2.1.2 Calculating Total System Accuracy
        3. 8.2.1.3 Compensating for Different Non-Ideality
  10. 9 Layout
    1. 9.1 PCB Layout for Minimizing Noise
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.1 Application Information

The LM95231 can be applied easily in the same way as other integrated-circuit temperature sensors, and its remote diode sensing capability allows it to be used in new ways as well. It can be soldered to a printed circuit board, and because the path of best thermal conductivity is between the die and the pins, its temperature will effectively be that of the printed circuit board lands and traces soldered to the LM95231's pins. This presumes that the ambient air temperature is almost the same as the surface temperature of the printed circuit board; if the air temperature is much higher or lower than the surface temperature, the actual temperature of the LM95231 die will be at an intermediate temperature between the surface and air temperatures. Again, the primary thermal conduction path is through the leads, so the circuit board temperature will contribute to the die temperature much more strongly than will the air temperature.

To measure temperature external to the LM95231's die, use a remote diode. This diode can be located on the die of a target IC, allowing measurement of the IC's temperature, independent of the LM95231's temperature. A discrete diode can also be used to sense the temperature of external objects or ambient air. Remember that a discrete diode's temperature will be affected, and often dominated, by the temperature of its leads. Most silicon diodes do not lend themselves well to this application. It is recommended that an MMBT3904 transistor base emitter junction be used with the collector tied to the base.

The LM95231's TruTherm technology allows accurate sensing of integrated thermal diodes, such as those found on processors. With TruTherm technology turned off, the LM95231 can measure a diode connected transistor such as the MMBT3904.

The LM95231 has been optimized to measure the remote thermal diode integrated in a Pentium 4 processor on 90nm process or an MMBT3904 transistor. Using the Remote Diode Model Select register either pair of remote inputs can be assigned to be either a Pentium 4 processor on 90nm process or an MMBT3904.