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

6.1 Overview

The LM95231 is a digital sensor that can sense the temperature of 3 thermal zones using a sigma-delta analog-to-digital converter. It can measure its local die temperature and the temperature of two external transistor junctions using a ΔVbe temperature sensing method. The LM95231 can support two external transistor types, a Pentium 4 processor on 90nm process thermal diode or a 2N3904 diode connected transistor. The transistor type is register programmable and does not require software intervention after initialization. The LM95231 has an advanced input stage using Texas Instruments' TruTherm technology that reduces the spread in non-ideality found in Pentium 4 processors on 90nm process. Internal analog filtering has been included in the thermal diode input stage thus minimizing the need for external thermal diode filter capacitors. In addition a digital filter has been added. These noise immunity improvements in the analog input stage along with the digital filtering will allow longer trace tracks or cabling to the thermal diode than previous thermal diode sensor devices.

The 2-wire serial interface, of the LM95231, is compatible with SMBus 2.0 and I2C. Please see the SMBus 2.0 specification for a detailed description of the differences between the I2C bus and SMBus.

The temperature conversion rate is programmable to allow the user to optimize the current consumption of the LM95231 to the system requirements. The LM95231 can be placed in shutdown to minimize power consumption when temperature data is not required. While in shutdown, a 1-shot conversion mode allows system control of the conversion rate for ultimate flexibility.

The remote diode temperature resolution is variable and depends on whether the digital filter is activated. When the digital filter is active the resolution is thirteen bits and is programmable to 13-bits unsigned or 12-bits plus sign, with a least-significant-bit (LSb) weight for both resolutions of 0.03125°C. When the digital filter is inactive the resolution is eleven bits and is programmable to 11-bits unsigned or 10-bits plus sign, with a least-significant-bit (LSb) weight for both resolutions of 0.125°C. The unsigned resolution allows the remote diodes to sense temperatures above 127°C. Local temperature resolution is not programmable and is always 9-bits plus sign and has a 0.25°C LSb.

The LM95231 remote diode temperature accuracy will be trimmed for the thermal diode of a Pentium 4 processor on 90nm process or a 2N3904 transistor and the accuracy will be ensured only when using either of these diodes when selected appropriately. TruTherm mode should be enabled when measuring a Pentium 4 processor on 90nm process and disabled when measuring a 2N3904 transistor. Enabling TruTherm mode with a 2N3904 transistor connected may produce unexpected temperature readings.

Diode fault detection circuitry in the LM95231 can detect the presence of a remote diode: whether D+ is shorted to VDD, D- or ground, or whether D+ is floating.

The LM95231 register set has an 8-bit data structure and includes:

  1. Most-Significant-Byte (MSB) Local Temperature Register
  2. Least-Significant-Byte (LSB) Local Temperature Register
  3. MSB Remote Temperature 1 Register
  4. LSB Remote Temperature 1 Register
  5. MSB Remote Temperature 2 Register
  6. LSB Remote Temperature 2 Register
  7. Status Register: busy, diode fault
  8. Configuration Register: resolution control, conversion rate control, standby control
  9. Remote Diode Filter Setting
  10. Remote Diode Model Select
  11. Remote Diode TruTherm Mode Control
  12. 1-shot Register
  13. Manufacturer ID
  14. Revision ID