MICROCHIP TC647BEUA

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 V_IN 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 V_MIN 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 V_MIN (pin 3) causes fan shutdown.

The TC642B and TC647B 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 missing pulse detector monitors this pin during fan operation. A stalled, open or unconnected fan causes the TC642B/ TC647B device to turn the V_OUT output on full (100% duty cycle). If the 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 V_OUT output is on full during the fan fault condition in order to attempt to restart the fan. FAULT is also asserted if the PWM reaches 100% duty cycle (TC642B only), indicating that maximum cooling capability has been reached and a possible overheating condition exists.

The TC642B and TC647B devices are available in 8-pin plastic MSOP, SOIC and PDIP packages. The specified temperature range of these devices is -40 to +85℃.

• Temperature-Proportional Fan Speed for Acousti 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

• Personal Computers & Servers
• LCD Projectors
• Datacom & Telecom Equipment
• Fan Trays
• File Servers
• General Purpose Fan Speed Control