TC648

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 TC648 Supply Voltage - Supports any Fan Voltage Over-temperature Fault Detection Automatic Shutdown Mode for “Green” Systems Supports Low Cost NTC/PTC Thermistors Space Saving 8-Pin MSOP Package TC648 Package Types SOIC/PDIP/MSOP VIN CF VAS GND 1 2 3 4 8 7 VDD VOUT OTF NC Fan Speed Controller with Auto-Shutdown and Over-Temperature Alert TC648 6 5 General Description The TC648 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 TC648 can be configured to operate in either auto-shutdown or minimum speed mode. In auto-shutdown mode, fan operation is automatically suspended when measured temperature (VIN) is lower than a user programmed minimum setting (VAS). The fan is automatically restarted, and proportional speed control restored, when VIN exceeds VAS (plus hysteresis). Operation in minimum speed mode is similar to auto-shutdown mode, with the exception that the fan is operated at a user programmed minimum setting when the measured temperature is low. An integrated Start-up Timer ensures reliable moto...