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