Description

The TC642B/TC647B devices are new versions of the existing TC642/TC647 fan speed controllers. These devices are switch mode, fan speed controllers that incorporate a new fan auto-restart function. Temperature-proportional speed control is accomplished using pulse width modulation. A thermistor (or other voltage output temperature sensor) connected to the VIN input supplies the required control voltage of 1.20V to 2.60V (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 start-up 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 Noise Reduction and Longer Fan Life

? Efficient PWM Fan Drive

? 3.0V to 5.5V Supply Range:

- Fan Voltage Independent of TC642B/TC647B Supply Voltage

- Supports any Fan Voltage

? FanSense? Fault Detection Circuit Protects Against Fan Failure and Aids System Testing

? Shutdown Mode for Green Systems

? Supports Low Cost NTC/PTC Thermistors

? Over-Temperature Indication (TC642B only)

? Fan Auto-Restart

? Space-Saving 8-Pin MSOP Package

Applications

? Personal Computers & Servers

? LCD Projectors

? Datacom & Telecom Equipment

? Fan Trays

? File Servers

? General Purpose Fan Speed Control