The TC642 is a switch mode fan speed controller for use with brushless DC motors. Temperature proportional speed control is accomplished using pulse width modulation. A thermistor (or other voltage output temperature sensor) connected to the VIN input furnishes the required control voltage of 1.25Vto 2.65V (typical) for 0% to 100% PWM duty cycle. Minimum fan speed is set by a simple resistor divider on the VMIN 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 VMIN, pin 3, causes fan shutdown. The TC642 also features Microchip Technology's proprietary FanSense™ technology for increasing system reliability. In normal fan operation, a pulse train is present at SENSE, pin 5, indicating normal operation. A missing-pulse detector monitors this pin during normal fan operation. A stalled, open, or unconnected fan causes the TC642 to trigger its start-up 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%
Parameter Name Value
Typical Accuracy (°C) Depends on external thermistor
Over Temp Alert yes
SM Bus NO
Predictive Fan Fault NO
Max. Supply Current (µA) 1000
Max. Accuracy @ 25°C (°C) Depends on external thermistor
Integrated Temp Sensor No
Fan Sense Yes
External Temp Input Yes
Auto Shutdown No
Device Description Fan Manager
Temp Range (°C) -40 to +85
Vcc Range (V) +3.0 to +5.5
Features
Temperature Proportional
Fan Speed for Acoustic Control and Longer Fan Life
Efficient PWM Fan Drive
3.0V 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
