SLVSIZ2 April   2026 FAN31790

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 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Power Supply
    6. 5.6 Fan Controller Characteristics
    7. 5.7 External Crystal Parameters
    8. 5.8 Digital IO
      1. 5.8.1 Electrical Characteristics
      2. 5.8.2 Switching Characteristics
    9. 5.9 I2C Characteristics
      1. 5.9.1 I2C Filter
      2. 5.9.2 I2C Timing Diagram
  7. 6 Detailed Description
    1. 6.1 Fan Control
      1. 6.1.1 PWM Mode
      2. 6.1.2 RPM Mode
      3. 6.1.3 Rate-of-Change Control
      4. 6.1.4 Spin-Up
      5. 6.1.5 Sequential Fan Start
      6. 6.1.6 FULL_SPEED Input
      7. 6.1.7 I2C Watchdog Timer
      8. 6.1.8 Power-on Reset Configuration Pins
    2. 6.2 Fan Monitoring
      1. 6.2.1 Tachometer Signals
      2. 6.2.2 PWM Outputs as Tachometer Inputs
    3. 6.3 Fan Faults and Failures
      1. 6.3.1 PWM Mode Failure Detection
      2. 6.3.2 RPM Mode Failure Detection
      3. 6.3.3 Locked Rotor Mode Failure Detection
      4. 6.3.4 Failure Indication
    4. 6.4 I2C Interface
      1. 6.4.1 I2C Addresses and ADDRx Pins
      2. 6.4.2 I2C Command Structure
  8. 7 Register Map
  9. 8 Register Descriptions
    1. 8.1 Global Configuration Registers
    2. 8.2 Fan Fault Registers
    3. 8.3 TACH and PWM Status Registers
    4. 8.4 PWM Duty Cycle Control Registers
    5. 8.5 TACH Target Count Registers
    6. 8.6 Window Registers
  10. 9 Application and Implementation
    1. 9.1 Typical Application
      1. 9.1.1 Schematic
      2. 9.1.2 Configuration Examples
  11. 10Device and Documentation Support
    1. 10.1 Receiving Notification of Documentation Updates
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Tape and Reel Information

封装选项

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机械数据 (封装 | 引脚)
  • ZFP|28
散热焊盘机械数据 (封装 | 引脚)
订购信息

6.1.7 I2C Watchdog Timer

The I2C watchdog timer monitors communication with the host system and forces fans to full speed if the host becomes unresponsive. This is a safety feature for data centers and mission-critical equipment. When enabled, the device tracks the time between I2C transactions and forces all fans to 100% duty cycle if no valid I2C transactions occur within a selected timeout period. The I2C Watchdog bits (2:1 in the Global Configuration register 00h) set the timeout to 5 seconds, 10 seconds, or 30 seconds, or watchdog disabled. The WD_START pin sets the power-up watchdog configuration. Once the watchdog times out it forces fans to full speed. Normal operation resumes if valid I2C transactions resume and the FAN31790 returns to its previous PWM values. The host must periodically communicate with each FAN31790 device to keep the watchdog satisfied. For example, by reading a status register.