General Description
The TC647 is a switch mode, fan speed controller for use with brushless DC fans. Temperature proportional speed control is accomplished using pulse width modulation (PWM). A thermistor (or other voltage output temperature sensor) connected to VIN furnishes the required control voltage of 1.25V to 2.65V (typical) for 0% to 100% PWM duty cycle. Minimum fan speed is set by a simple resistor divider on the VMIN input. An integrated Start-up Timer ensures reliable motor startup at turn-on, coming out of shutdown mode or following a transient fault. A logic low applied to VMIN (Pin 3) causes fan shutdown.

Features
• Temperature Proportional Fan Speed for Acoustic Control and Longer Fan Life
• Efficient PWM Fan Drive
• 3.0V to 5.5V Supply Range:
   - Fan Voltage Independent of TC647 Supply Voltage
   - Supports any Fan Voltage
• FanSense™ Technology Fault Detection Circuits Protect Against Fan Failure and Aid System Testing
• Shutdown Mode for "Green" Systems
• Supports Low Cost NTC/PTC Thermistors
• Space Saving 8-Pin MSOP Package

Applications
• Power Supplies
• Personal Computers
• File Servers
• Telecom Equipment
• UPSs, Power Amps
• General Purpose Fan Speed Control