SMBus PWM fan speed controller

The TC665 is an SMBus PWM fan speed controller with fan fault detection intended for use with brushless DC motors. This device permits temperature proportional speed control and therefore accomplishes lower acoustic fan noise and longer fan life. The TC665 reads the voltage provided by an external thermistor (or voltage output temperature sensor) and adjusts a 30% to 100% PWM duty cycle output to the fan with respect to the input temperature voltage. The PWM duty cycle can also be programmed via SMBus to allow fan speed control without the need of an external thermistor.

In normal fan operation, pulse trains are present at the SENSE pin. These pulses are used to calculate the fan RPM. The fan RPM data is used to detect a worn out, stalled, open or unconnected fan. An RPM level below the user-programmable threshold causes the TC665 to assert a logic low alert signal (FAULT). The default value is 500RPM. The TC665 consumes only 0.3mA during operation and can also enter a low-power shutdown mode by setting the appropriate bit in the configuration register. 

Features

• Temperature Proportional Fan Speed for Acoustic Control and Longer Fan Life
• FanSense™ Protects Against Fan Failure
• Provides RPM Data
• Over-Temperature Detection
• 2-wire SMBus Compatible Interface
• 3.0V to 5.5V Supply Range
• Fan Voltage Independent of Supply Voltage
  – Supports Any Fan Voltage
• Supports Low Cost NTC/PTC Thermistors