TC646

Features:

• 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 TC646 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




Application

• Power Supplies
• Computers
• File Servers
• Portable Computers
• Telecom Equipment
• UPS, Power Amps
• General Purpose Fan Speed Control




Specifications

Parameter NameValueTypical Accuracy (°C)Depends on external thermistorOver Temp AlertyesSM BusNOPredictive Fan FaultNOMax. Supply Current (A)1000Max. Accuracy @ 25°C (°C)Depends on external thermistorIntegrated Temp SensorNoFan SenseYesExternal Temp InputYesAuto ShutdownYesDevice DescriptionFan ManagerTemp Range (°C)-40 to +85Vcc Range (V)+3.0 to +5.5

Parameter Name	Value
Typical Accuracy (°C)	Depends on external thermistor
Over Temp Alert	yes
SM Bus	NO
Predictive Fan Fault	NO
Max. Supply Current (A)	1000
Max. Accuracy @ 25°C (°C)	Depends on external thermistor
Integrated Temp Sensor	No
Fan Sense	Yes
External Temp Input	Yes
Auto Shutdown	Yes
Device Description	Fan Manager
Temp Range (°C)	-40 to +85
Vcc Range (V)	+3.0 to +5.5

Supply Voltage ............................................................6V
Input Voltage, Any Pin..... (GND  0.3V) to (VDD+0.3V)
Package Thermal Resistance:
PDIP (RJA).......................................................125°C/W
SOIC (RJA) .....................................................155°C/W
MSOP (RJA) ....................................................200°C/W
Specified Temperature Range ........... -40°C to +125°C
Storage Temperature Range.............. -65°C to +150°C

Description

The TC646 is a switch mode fan speed controller for use with brushless DC motors. Temperature proportional speed control is accomplished using pulse width modulation(PWM). A thermistor (or other voltage output temperature sensor)connected to the VIN input furnishes the required control voltage of 1.25V to 2.65V(typical) for 0% to 100% PWM duty cycle. The TC646 automatically suspends fan operation when measured temperature (VIN) is below a user-programmed minimum setting (VAS). An integrated Start-Up Timer ensures reliable motor start-up at turn-on, coming out of Shutdown mode, or following a transient fault. In normal fan operation, a pulse train is present at SENSE, pin 5. The TC646 also features Microchip Technology's proprietary FanSense™ TM technology for increasing system reliability. A missing-pulse detector monitors this pin during fan operation. A stalled, open, or unconnected fan causes the TC646 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. See the Applications section for more information and system design guidelines. The TC646 is packaged in a space-saving 8-pin plastic DIP, MSOP or SOIC package and is available in the industrial temperature range.

The TC646 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 VIN input furnishes the required control voltage of 1.25V to 2.65V (typical) for 0% to 100% PWM duty cycle. The TC646 automatically suspends fan operation when measured temperature (VIN) is below a user programmed minimum setting (VAS). An integrated Start-up Timer ensures reliable motor start-up at turn-on, coming out of shutdown mode, auto-shutdown mode or following a transient fault.

The TC646 features 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 TC646 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% duty cycle, indicating a possible thermal runaway situation, although the fan continues to run. See Section 5.0, "Typical Applications", for more information and system design guidelines.

The TC646 is available in the 8-pin plastic DIP, SOIC and MSOP packages and is available in the industrial and extended commercial temperature ranges.