TC648 - Microchip Technology

1 2001-2012 Microchip Technology 1TC648 Features Temperature Proportional Fan Speed for Acoustic Control and Longer Fan Life Efficient PWM Fan Drive to Supply Range:- Fan Voltage Independent of TC648 Supply Voltage- Supports any Fan Voltage Over-temperature Fault Detection Automatic Shutdown Mode for Green Systems Supports Low Cost NTC/PTC Thermistors Space Saving 8-Pin MSOP PackageApplications Power Supplies Computers Portable Computers Telecom Equipment UPSs, Power Amps General Purpose Fan Speed ControlAvailable Tools Fan Controller Demonstration Board (TC642 DEMO) Fan Controller Evaluation Kit (TC642EV)

2 Package TypesGeneral DescriptionThe TC648 is a switch mode, fan speed controller foruse with brushless DC fans. Temperature proportionalspeed control is accomplished using pulse width mod-ulation (PWM). A thermistor (or other voltage outputtemperature sensor) connected to the VIN inputfurnishes the required control voltage of to (typical) for 0% to 100% PWM duty cycle. The TC648can be configured to operate in either auto-shutdown orminimum speed mode. In auto-shutdown mode, fanoperation is automatically suspended when measuredtemperature (VIN) is lower than a user programmedminimum setting (VAS).

3 The fan is automaticallyrestarted, and proportional speed control restored,when VIN exceeds VAS (plus hysteresis). Operation inminimum speed mode is similar to auto-shutdownmode, with the exception that the fan is operated at auser programmed minimum setting when the mea-sured temperature is low. An integrated Start-up Timerensures reliable motor start-up at turn-on, and whencoming out of shutdown or auto-shutdown over-temperature fault output (OTF) is assertedwhen the PWM reaches 100% duty cycle, indicating apossible thermal runaway situation.

4 The TC648 is available in the 8-pin plastic DIP, SOICand MSOP packages and is available in the industrialand extended commercial temperature Speed Controller with Auto-Shutdownand Over-Temperature AlertTC648DS21448D-page 2 2001-2012 Microchip Technology Block DiagramOTFSHDNNCPWMOTFGNDVASVSHDNVINCFVD DVOUTTC648 ControlLogic+ VOTF+ + + Start-upTimerClockGenerator 2001-2012 Microchip Technology CHARACTERISTICSA bsolute Maximum Ratings*Supply Voltage .. 6 VInput Voltage, Any (GND ) to (VDD + )Package Thermal Resistance:PDIP (R JA).

5 125 C/WSOIC (R JA) .. 155 C/WMSOP (R JA) .. 200 C/WSpecified Temperature -40 C to +125 CStorage Temperature Range .. -65 C to +150 C*Stresses above those listed under "Absolute Maximum Rat-ings" may cause permanent damage to the device. These arestress ratings only and functional operation of the device atthese or any other conditions above those indicated in theoperation sections of the specifications is not implied. Expo-sure to absolute maximum rating conditions for extended peri-ods may affect device ELECTRICAL SPECIFICATIONSE lectrical Characteristics: Unless otherwise specified, TMIN TA TMAX, VDD = to MaxUnitsTest ConditionsVDDS upply Current, Operating 6, 7 Open, CF = 1 F, VIN = VC(MAX)IDD(SHDN)Supply Current, Shutdown/ Auto-shutdown Mode 25 APins 6, 7 Open.

6 Note 1CF =1 F, VIN = , VAS Input + ANote 1 VOUT OutputtRVOUT Rise Time 50 sec IOH = 5 mA, Note 1tFVOUT Fall Time 50 sec IOL = 1 mA, Note 1 IOLSink Current at VOUT mAVOL = 10% of VDDIOHS ource Current at VOUT mAVOH = 80% of VDDSENSE InputVTH(SENSE)SENSE Input Threshold Voltage with Respect to GND507090mVNote 1 OTF OutputVOLO utput Low Voltage = mAVIN, VAS InputsVC(MAX),VOTFV oltage at VIN for 100% Duty Cycle and Overtemp. (SPAN)VC(MAX) - VC(MIN) Threshold VC(MAX) ~ VC(SPAN) VC(MAX) VVSHDNV oltage Applied to VIN to Ensure Reset/Shutdown VDD x Applied to VIN to Release Reset ModeVDD x VVDD = 5 VVHYSTH ysteresis on VSHDN, VREL x VDD VVHASH ysteresis on Auto-shutdown Comparator 70 mVNote 1:Ensured by design, not 4 2001-2012 Microchip Technology Width ModulatorFOSCPWM Frequency2630 34 HzCF = FtSTARTUPS tart-up Timer 32/F SecCF = FDC ELECTRICAL SPECIFICATIONS (CONTINUED)Electrical Characteristics.

7 Unless otherwise specified, TMIN TA TMAX, VDD = to MaxUnitsTest ConditionsNote 1:Ensured by design, not tested. 2001-2012 Microchip Technology DESCRIPTIONSThe descriptions of the pins are listed in Table 2-1:PIN FUNCTION Input (VIN)The thermistor network (or other temperature sensor) connects to the VIN input. A voltage range of to (typical) on this pin drives an active duty cycle of 0% to 100% on the VOUT pin (see Section , Typical Applications , for more details). Output (CF)CF is the positive terminal for the PWM ramp generatortiming capacitor.

8 The recommended CF is 1 F for30 Hz PWM Input (VAS)An external resistor divider connected to the VAS inputsets the auto-shutdown threshold. Auto-shutdownoccurs when VIN VAS. During shutdown, supplycurrent falls to 25 A (typical). The fan is automaticallyrestarted when VIN (VAS +VHAS) (see Section , Typical Applications for more details). (GND)GND denotes the ground ConnectNo internal Output (OTF)OTF goes low to indicate an over-temperaturecondition. This occurs when the voltage at VIN > VOTF(see Section , "Electrical Characteristics").

9 An over-temperature indication is a non-latching Output (VOUT)VOUT is an active high complimentary output that drivesthe base of an external NPN transistor (via an appropri-ate base resistor) or the gate of an N-channel MOS-FET. This output has asymmetrical drive (seeSection , Electrical Characteristics ). Supply Input (VDD)VDD may be independent of the fan s power supply(see Section , Electrical Characteristics ).Pin Input2 CFAnalog Output3 VASA nalog Input4 GNDG round Terminal5 NCNo Internal Connection6 OTFD igital (Open Collector) Output7 VOUTD igital Output8 VDDP ower Supply InputTC648DS21448D-page 6 2001-2012 Microchip Technology PWM circuit consists of a ramp generator andthreshold detector.

10 The frequency of the PWM isdetermined by the value of the capacitor connected tothe CF pin. A frequency of 30 Hz is recommended formost applications (CF = 1 F). The PWM is also thetime base for the Start-up Timer (see Section , Start-up Timer ). The PWM voltage control range to (typical) for 0% to 100% output OutputThe VOUT pin is designed to drive a low cost transistoror MOSFET as the low side power switching element inthe system. Various examples of driver circuits will beshown throughout this data sheet.