TC74 - Microchip Technology

1 2001-2012 Microchip Technology 1TC74 Features Digital Temperature Sensing in SOT-23-5 or TO-220 Packages Outputs Temperature as an 8-Bit Digital Word Simple SMBus/I2C Serial Port Interface Solid-State Temperature Sensing:- 2 C (max.) Accuracy from +25 C to +85 C- 3 C (max.) Accuracy from 0 C to +125 C Supply Voltage of to Low Power:- 200 A (typ.) Operating Current- 5 A (typ.) Standby Mode CurrentApplications Thermal Protection for Hard Disk Drives and other PC Peripherals PC Card Devices for Notebook Computers Low Cost Thermostat Controls Power Supplies Thermistor ReplacementPackage TypesGeneral DescriptionThe TC74 is a serially accessible, digital temperaturesensor particularly suited for low cost and small form-factor applications.

2 Temperature data is converted fromthe onboard thermal sensing element and madeavailable as an 8-bit digital with the TC74 is accomplished via a 2-wire SMBus/I2C compatible serial port. This bus alsocan be used to implement multi-drop/multi-zonemonitoring. The SHDN bit in the CONFIG register canbe used to activate the low power Standby resolution is 1 C. Conversion rate is anominal 8 samples/sec. During normal operation, thequiescent current is 200 A (typ). During standbyoperation, the quiescent current is 5 A (typ).Small size, low installed cost and ease of use make theTC74 an ideal choice for implementing thermalmanagement in a variety of Block DiagramGNDVDDNCSDASCLKTO-220 SOT-23 VDDGND12NC54 SDASCLKTC74312345TC74 Note: The TO-220 tab is connectedto pin 3 (GND)Internal Sensor(Diode) ModulatorTemperatureRegisterSerial PortInterfaceControlLogicSDASCLKTiny Serial Digital Thermal SensorTC74DS21462D-page 2 2001-2012 Microchip Technology Maximum Ratings Supply Voltage (VDD).

3 +6 VVoltage On Any Pin .. (GND ) to (VDD + )Current On Any Pin .. 50 mAOperating Temperature (TA) .. -40 C TA +125 CStorage Temperature (TSTG) ..-65 C to +150 CJunction Temperature (TJ).. +150 C Notice: Stresses above those listed under "MaximumRatings" may cause permanent damage to the is a stress rating only and functional operation ofthe device at those or any other conditions above thoseindicated in the operation listings of this specification isnot implied. Exposure to maximum rating conditions forextended periods may affect device CHARACTERISTICSE lectrical Specifications: Unless otherwise noted, VDD = for and VDD = for , -40 C TA 125 C.

4 Note 5 ParametersSymMinTypMaxUnitsConditionsPow er SupplyPower-on Reset Falling Edge or Rising EdgeSupply 5 Operating CurrentIDD 200350 AVDD = , Note 1 Standby Supply CurrentIDD-STANDBY AVDD = Port Inactive, Note 4 Temperature-to-Bits ConverterTemperature + + C+25 C <TA < +85 C 0 C < TA < +125 C-40 C < TA < 0 CConversion RateCR48 SPSNote 2 Serial Port InterfaceLogic Input x VDD VLogic Input LowVIL x VDDVSDA Output LowVOL = 3 mAIOL = 6 mA, Note 3 Input Capacitance SDA, SCLKCIN pFI/O ASerial Port AC Timing (CLOAD = 80 pF)SMBus/I2C Clock FrequencyfSMB10 100kHzLow Clock sec 10% to 10%High Clock sec 90% to 90%SMBus/I2C Rise TimeSMBus/I2C Fall TimetRtF 1000300nsecnsec10% to 90%90% to10%Note 1:Operating current is an average value integrated over multiple conversion cycles.

5 Transient current may exceed this :Maximum ensured conversion time after Power-on Reset (POR to DATA_RDY) is 250 :Output current should be minimized for best temperature accuracy. Power dissipation within the TC74 will cause self-heating and temperature drift :SDA and SCLK must be connected to VDD or :VDD = for TC74AX VXX. VDD = for TC74AX VXX. All part types of the TC74 will operate properly over the wider power supply range of to Each part type is tested and specified for rated accuracy at its nominal supply voltage. As VDD varies from the nominal value, accuracy will degrade 1 C/V of VDD change. 2001-2012 Microchip Technology 3TC74 START Condition Setup Time(for repeated START Condition)tSU(START) sec 90% SCLK to 10% SDASTART Condition Hold TimetH(START) secData In Setup TimetSU-DATA1000 nsecData In Hold TimetH-DAT1250 nsecSTOP Condition Setup TimetSU(STOP) secBus Free Time Prior to New secPower-on Reset Delay tPOR 500 secVDD VPOR (Rising Edge)DC CHARACTERISTICS (CONTINUED)Electrical Specifications: Unless otherwise noted, VDD = for and VDD = for , -40 C TA 125 C.

6 Note 5 ParametersSymMinTypMaxUnitsConditionsNot e 1:Operating current is an average value integrated over multiple conversion cycles. Transient current may exceed this :Maximum ensured conversion time after Power-on Reset (POR to DATA_RDY) is 250 :Output current should be minimized for best temperature accuracy. Power dissipation within the TC74 will cause self-heating and temperature drift :SDA and SCLK must be connected to VDD or :VDD = for TC74AX VXX. VDD = for TC74AX VXX. All part types of the TC74 will operate properly over the wider power supply range of to Each part type is tested and specified for rated accuracy at its nominal supply voltage.

7 As VDD varies from the nominal value, accuracy will degrade 1 C/V of VDD 4 2001-2012 Microchip Technology 1-1:Timing = LSB of Address Clocked into Slave tSU(START)tH(START)tSU-DATAtSU(STOP)tIDL EA = Start Condition B = MSB of Address Clocked into Slave C = LSB of Address Clocked into Slave D = R/W Bit Clocked into Slave ABCDEF G HIJKE = Slave Pulls SDA Line Low F = Acknowledge Bit Clocked into Master G = MSB of Data Clocked into Master H = LSB of Data Clocked into Master tLOWtHIGHI = Acknowledge Clock Pulse J = Stop Condition K = New Start ConditionSCLKSDASMBUS Read Timing DiagramtSU(START)tH(START)tSU-DATAtSU(ST OP)tIDLEA = Start Condition B = MSB of Address Clocked into Slave D = R/W Bit Clocked into Slave E = Slave Pulls SDA Line LowABCDEF G HIJKLMF = Acknowledge Bit Clocked into Master G = MSB of Data Clocked into Slave H = LSB of Data Clocked into Slave I = Slave Pulls SDA Line LowJ = Acknowledge Clocked into Master K = Acknowledge Clock Pulse L = Stop Condition, Data Executed by Slave M = New Start ConditiontLOWtHIGHSCLKSDAtH-DATASMBUS Write Timing Diagram 2001-2012 Microchip Technology DESCRIPTIONSThe descriptions of the pins are listed in Table 2-1:PIN FUNCTION (GND)Input.

8 Ground return for all TC74 Supply Input (VDD)Power supply input. See Electrical Serial Clock (SCLK)Input. SMBus/I2C serial clock. Clocks data into and outof the TC74. See System Management BusSpecification, Rev. , for timing Data (SDA)Bidirectional. Serial data is transferred on the SMBus/I2C in both directions using this pin. See SystemManagement Bus Specification, Rev. for No.(5-Pin SOT-23)Pin No.(5-Pin TO-220)SymbolTypeDescription11 NCNoneNo Internal Connection23 GNDP owerSystem Ground35 VDDP owerPower Supply Input44 SCLKI nputSMBus/I2C Serial Clock52 SDAB idirectionalSMBus/I2C Serial DataTC74DS21462D-page 6 2001-2012 Microchip Technology DescriptionThe TC74 acquires and converts temperatureinformation from its onboard solid-state sensor with aresolution of 1 C.

9 It stores the data in an internalregister which is then read through the serial port. Thesystem interface is a slave SMBus/I2C port, throughwhich temperature data can be read at any time. EightSMBus/I2C addresses are programmable for the TC74,which allows for a multi-sensor configuration. Also,there is low power Standby mode when temperatureacquisition is MODEThe host is allowed, by the TC74, to put it into a lowpower (IDD = 5 A, typical) Standby mode. In this mode,the A/D converter is halted and the temperature dataregisters are frozen. The SMBus/I2C port, though,operates normally. Standby mode is enabled by settingthe SHDN bit in the CONFIG register.

10 Table 3-1summarizes this 3-1:STANDBY MODE SLAVE ADDRESSThe TC74 is internally programmed to have a defaultSMBus/I2C address value of 1001 101b. Seven otheraddresses are available by custom order (contactMicrochip Technology Port OperationThe Serial Clock input (SCLK) and bidirectional dataport (SDA) form a 2-wire bidirectional serial port for pro-gramming and interrogating the TC74. Theconventions used in this bus architecture are listed inTable 3-2:SERIAL BUS CONVENTIONSAll transfers take place under the control of a host, usu-ally a CPU or microcontroller, acting as the Master. Thishost provides the clock signal for all transfers.)