MICROCHIP TC642VPA

The TC642 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 V_IN input furnishes the required control voltage of 1.25V to 2.65V (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 TC642 also features 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 TC642 to trigger its Startup Timer once. If the fault persists, the FAULT output goes low and the device is latched in its shutdown mode. FAULT is also asserted if the PWM reaches 100% duty cycle, indicating a possible thermal runaway situation, although the fan continues to run. The TC642 is available in the standard 8-pin plastic DIP, SOIC and MSOP packages and is available in the commercial, extended commercial and industrial temperature ranges.

• 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 TC642 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

• Power Supplies
• Personal Computers
• File Servers
• Telecom Equipment
• UPSs, Power Amps, etc.
• General Purpose Fan Speed Control