TC646

M 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 TC646 Supply Voltage - Supports any Fan Voltage FanSense™ 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 Over-temperature Indication TC646 Package Types SOIC/PDIP/MSOP VIN CF VAS GND 1 2 3 4 8 VDD VOUT FAULT SENSE PWM Fan Speed Controller with Auto-Shutdown and FanSense™ Technology TC646 7 6 5 General Description The TC646 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 the VIN input furnishes the required control voltage of 1.25V to 2.65V (typical) for 0% to 100% PWM duty cycle. The TC646 automatically suspends fan operation when measured temperature (VIN) is below a user programmed minimum setting (VAS). An integrated Start-up Timer ensures reliable motor start-up at turn-on, coming out of shutdown mode, auto-shutdown mode or following a transient fault. The TC646 features Microchip Technology's proprietary FanSense™ technology for increasing system reliability. In normal fan operation, a pulse train is present at SENSE (Pin 5). A missing-pulse detector monitors this pin during...