TC646B/TC648B/TC649B PWM Fan Speed Controllers With Auto-Shutdown, Fan Restart and FanSense Technology for Fault Detection Features Description Temperature-Proportional Fan Speed for Acoustic The TC646B/TC648B/TC649B devices are new ver- Noise Reduction and Longer Fan Life sions of the existing TC646/TC648/TC649 fan speed controllers. These devices are switch-mode fan speed Efficient PWM Fan Drive controllers that incorporate a new fan auto-restart func- 3.0V to 5.5V Supply Range: tion. Temperature-proportional speed control is accom- - Fan Voltage Independent of TC646B/ plished using pulse width modulation. A thermistor (or TC648B/TC649B Supply Voltage other voltage output temperature sensor) connected to - Supports any Fan Voltage the V input supplies the required control voltage of IN Fault Detection Circuit Protects FanSense 1.20V to 2.60V (typical) for 0% to 100% PWM duty Against Fan Failure and Aids System Testing cycle. The auto-shutdown threshold/temperature is set (TC646B/TC649B) by a simple resistor divider on the V input. An inte- AS grated Start-Up Timer ensures reliable fan motor start- Automatic Shutdown Mode for Green Systems up at turn-on, coming out of shutdown mode, auto- Supports Low Cost NTC/PTC Thermistors shutdown mode or following a transient fault. A logic Over-Temperature Indication (TC646B/TC648B) low applied to V (pin 1) causes fan shutdown. IN Fan Auto-Restart The TC646B and TC649B also feature Microchip Space-Saving 8-Pin MSOP Package Technology s proprietary FanSense technology for increasing system reliability. In normal fan operation, a Applications pulse train is present at SENSE (pin 5). A missing- pulse detector monitors this pin during fan operation. A Personal Computers & Servers stalled, open or unconnected fan causes the TC646B/ LCD Projectors TC649B device to turn the V output on full (100% OUT Datacom & Telecom Equipment duty cycle). If the fan fault persists (a fan current pulse Fan Trays is not detected within a 32/f period), the FAULT output File Servers goes low. Even with the FAULT output low, the V OUT output is on full during the fan fault condition in order to General-Purpose Fan Speed Control attempt to restart the fan. FAULT (TC646B) or OTF (TC648B) is also asserted if the PWM reaches 100% Package Types duty cycle, indicating that maximum cooling capability has been reached and a possible overheating condition MSOP, PDIP, SOIC exists. The TC646B, TC648B and TC649B devices are avail- V 1 8 V IN DD able in 8-pin plastic MSOP, SOIC and PDIP packages. The specified temperature range of these devices is C 2 7 V F OUT TC646B -40 to +85C. TC649B V 3 6 FAULT AS GND 4 SENSE 5 V 1 8 V IN DD C 2 7 V F OUT TC648B V 3 6 OTF AS GND 4 NC 5 2002-2013 Microchip Technology Inc. DS21755C-page 1TC646B/TC648B/TC649B Functional Block Diagram TC646B/TC649B V OTF V V IN DD Note Note: The V comparator OTF Control is for the TC646B device only. Logic C Clock F 3xT PWM V Generator OUT Timer Start-up V AS Timer FAULT V SHDN Missing Pulse Detect SENSE 10 k GND 70 mV (typ) TC648B V OTF V V IN DD Control Logic C Clock F Generator V OUT Start-up V AS Timer OTF V SHDN NC GND DS21755C-page 2 2002-2013 Microchip Technology Inc.