SNAS207B May   2004  – January 2024 LM64

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 DC Electrical Characteristics
    4. 5.4 Operating Electrical Characteristics
    5. 5.5 AC Electrical Characteristics
    6. 5.6 Digital Electrical Characteristics
    7. 5.7 SMBus Logical Electrical Characteristics
    8. 5.8 SMBus Digital Switching 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  The ALERT Output
        1. 6.3.2.1 ALERT Output as a Temperature Comparator
        2. 6.3.2.2 ALERT Output as an Interrupt
        3. 6.3.2.3 ALERT Output as an SMBus ALERT
      3. 6.3.3  SMBus Interface
      4. 6.3.4  Power-On Reset (POR) Default States
      5. 6.3.5  Temperature Data Format
      6. 6.3.6  Open-Drain Outputs, Inputs, and Pull-Up Resistors
      7. 6.3.7  Diode Fault Detection
      8. 6.3.8  Communicating with the LM64
      9. 6.3.9  Digital Filter
      10. 6.3.10 Fault Queue
      11. 6.3.11 One-Shot Register
      12. 6.3.12 Serial Interface Reset
  8. 7 Registers
    1. 7.1 LM64 Registers
      1. 7.1.1 LM64 Register Map in Hexadecimal Order
      2. 7.1.2 LM64 Register Map in Functional Order
      3. 7.1.3 LM64 Initial Register Sequence and Register Descriptions in Functional Order
        1. 7.1.3.1 LM64 Required Initial Fan Control Register Sequence
      4. 7.1.4 LM64 Register Descriptions in Functional Order
        1. 7.1.4.1 Fan Control Registers
        2. 7.1.4.2 Configuration Register
        3. 7.1.4.3 Tachometer Count And Limit Registers
        4. 7.1.4.4 Local Temperature And Local High Setpoint Registers
        5. 7.1.4.5 Remote Diode Temperature, Offset And Setpoint Registers
        6. 7.1.4.6 ALERT Status And Mask Registers
        7. 7.1.4.7 Conversion Rate And One-Shot Registers
        8. 7.1.4.8 ID Registers
    2. 7.2 General Purpose Registers
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Fan Control Duty Cycle VS. Register Settings and Frequency
        1. 8.1.1.1 Computing Duty Cycles for a Given Frequency
      2. 8.1.2 Use of the Lookup Table for Non-Linear PWM Values VS Temperature
      3. 8.1.3 NON-Ideality Factor and Temperature Accuracy
        1. 8.1.3.1 Diode Non_Ideality
        2. 8.1.3.2 Compensating for Diode Non-Ideality
      4. 8.1.4 Computing RPM of the Fan from the TACH Count
    2. 8.2 Typical Application
  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

6.3.5 Temperature Data Format

Temperature data can only be read from the Local and Remote Temperature registers. The High, Low and T_CRIT setpoint registers are Read/Write.

Remote temperature data is represented by an 11-bit, two's complement word with a Least Significant Bit (LSB) equal to 0.125°C. The data format is a left justified 16-bit word available in two 8-bit registers. Some examples of temperature conversions are shown below.

Table 6-1 Actual vs. LM64 Remote Temperature Conversion(1)
Actual Remote Diode Temperature,°C LM64 Remote Diode Temperature Register, °C Binary Results in LM64 Remote Temperature Register Hex Remote Temperature Register
120 +104 0110 1000 0000 0000 6800h
125 +109 0110 1101 0000 0000 6D00h
126 +110 0110 1110 0000 0000 6E00h
130 +114 0111 0010 0010 0000 7200h
135 +119 0111 0111 0000 0000 7700h
140 +124 0111 1100 0000 0000 7C00h
(1) Output is 11-bit two's complement word. LSB = 0.125 °C.
Table 6-2 Actual vs. Remote T_Crit Setpoint Example
Actual Remote Diode T_Crit Setpoint,°CRemote T_CRIT
High Setpoint, °C		Binary Remote T_CRIT
High Setpoint Value		Hex Remote T_CRIT High Setpoint Value
126+1100110 11106Eh

Local Temperature data is represented by an 8-bit, two's complement byte with an LSB equal to 1°C:

TemperatureDigital Output
BinaryHex
+125°C0111 11017D
+25°C0001 100119
+1°C0000 000101
0°C0000 000000
−1°C1111 1111FF
−25°C1110 0111E7
−55°C1100 1001C9