TC646B/TC648B/TC649B
PWM Fan Speed Controllers With Auto-Shutdown, Fan
Restart and FanSenseв„ў Technology for Fault Detection
Features Description 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 TC646B/
TC648B/TC649B Supply Voltage
-Supports any Fan Voltage FanSenseв„ў Fault Detection Circuit Protects
Against Fan Failure and Aids System Testing
(TC646B/TC649B) Automatic Shutdown Mode for “Green” Systems Supports Low Cost NTC/PTC Thermistors Over-Temperature Indication (TC646B/TC648B) Fan Auto-Restart Space-Saving 8-Pin MSOP Package The TC646B/TC648B/TC649B devices are new versions of the existing TC646/TC648/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. Applications Personal Computers & Servers
LCD Projectors
Datacom & Telecom Equipment
Fan Trays
File Servers
General-Purpose Fan Speed Control Package Types …