TC649BEOA

The TC649B device is new versions of the existing TC649 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. The auto-shutdown threshold/temperature is set by a simple resistor divider on the VAS input. An integrated Start-Up Timer ensures reliable fan motor startup at turn-on, coming out of shutdown mode, autoshutdown mode or following a transient fault. A logic low applied to VIN (pin 1) causes fan shutdown. The TC649B also feature Microchip Technology's proprietary FanSense technology for increasing system reliability. In normal fan operation, a pulse train is present at SENSE (pin 5). A missingpulse detector monitors this pin during fan operation. A stalled, open or unconnected fan causes the TC649B device to turn the VOUT output on full (100% duty cycle). If the fan fault persists (a fan current pulse is not detected within a 32/f period), the FAULT output goes low. Even with the FAULT output low, the VOUT output is on full during the fan fault condition in order to attempt to restart the fan. The TC649B devices are available in 8-pin plastic MSOP, SOIC and PDIP packages. The specified temperature range of these devices is -40 to +85°C.

• 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 TC649B Supply Voltage - Supports any Fan Voltage
• FanSense™ Fault Detection Circuit Protects Against Fan Failure and Aids System Testing (TC649B)
• Automatic Shutdown Mode for “Green” Systems
• Supports Low Cost NTC/PTC Thermistors
• Fan Auto-Restart
• Space-Saving 8-Pin MSOP Package