TC647B

M TC642B/TC647B PWM Fan Speed Controllers With Minimum Fan Speed, Fan Restart and FanSense™ Technology for Fault Detection 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 Package Types MSOP, PDIP, SOIC VIN CF VMIN GND 1 2 3 4 TC642B TC647B 8 VDD 7 VOUT 6 FAULT 5 SENSE 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, ...