MC74 Serial Digital Temperature Sensor The MC74 is a serial digital temperature sensor suited for low cost applications. Temperature data is converted from the integrated thermal sensing element and made available as an 8–bit serial digital word. Communication with the MC74 is accomplished via 2–wire SMBus/I2C–compatible serial port. Temperature resolution is 1°C. Conversion rate is a nominal 8 samples/sec. Power consumption is only 200 µA (5 µA Standby). Features • Tested Operating Temperature Range: –40°C to +125°C • Simple Serial Port Interface • Solid State Temperature Sensing: ±2°C Accuracy from +25°C to +85°C ±3°C Accuracy from 0°C to +125°C • 3.3V and 5.5V Versions http://onsemi.com SOT–23–5 SN SUFFIX CASE TBD PRELIMINARY INFORMATION Typical Applications • Thermal Protection for Hard Disk Drives and Other PC Peripherals • Low–Cost Thermostat Controls • Power Supplies PIN CONFIGURATION (Top View) NC 1 GND 2 VDD 3 5 SDA FUNCTIONAL BLOCK DIAGRAM Internal Sensor (Diode) Serial Port Interface 4 SCL SDA SOT–23–5* SCL NOTE: *SOT–23–5 is equivalent to EIAJ–SC74A DS Modulator Control Logic Temperature Register 1 5 TO–220–5 T SUFFIX CASE TBD PRELIMINARY INFORMATION ORDERING INFORMATION Semiconductor Components Industries, LLC, 1999 February, 2000 – Rev. 0 1 Device Package Voltage MC74A5–33SNTR SOT–23–5 3.3V VDD MC74A5–50T TO–220–5 5.0V VDD Publication Order Number: MC74/D MC74 PIN DESCRIPTION FOR TO–220–5 ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Pin No. Symbol Type Description 1 NC None 2 SDA Bi–directional 3 GND Power 4 SCL Input SMBus Serial Clock 5 VDD Power Power Supply Input Not Connected SMBus Serial Data System Ground PIN DESCRIPTION FOR SOT–23–5 Pin No. Symbol Type 1 NC None Not Connected Description 2 GND Power System Ground 3 VDD Power Power Supply Input 4 SCL Input SMBus Serial Clock 5 SDA Bi–directional SMBus Serial Data PIN DESCRIPTION SCL VDD Input. SMBus serial clock. Clocks data into and out of the MC74. See System Management Bus Specification, rev. 1.0, for timing diagrams. Input. Power supply input. See electrical specifications. GND Input. Ground return for all MC74 functions. SDA Bi–directional. Serial data is transferred on the SMBus in both directions using this pin. See System Management Bus Specification rev. 1.0 for timing diagrams. ABSOLUTE MAXIMUM RATINGS* Symbol VDD Parameter Power Supply Voltage Voltage on Any Pin Value Unit 6.0 V (GND – 0.3 V) to (VDD + 0.3 V) V °C TA Operating Temperature Range –40 to +125 Tstg Storage Temperature Range PD –65 to +150 °C Current on Any Pin ±50 mA Maximum Power Dissipation 330 mW * Maximum Ratings are those values beyond which damage to the device may occur. http://onsemi.com 2 MC74 DC ELECTRICAL CHARACTERISTICS (VDD = 3.3 V or 5.0V (5), –40°C ≤ TA ≤ 125°C, unless otherwise noted.) Characteristic Min Typ Max Power–On Reset Threshold (VDD Falling Edge or Rising Edge) 1.2 — 2.2 Operating Current (VDD = 5.5V, Serial Port Inactive) (1) — 200 350 Standby Supply Current (VDD = 3.3 V, Serial Port Inactive) (4) — 5.0 10 –2.0 –3.0 — — — ±2.0 +2.0 +3.0 — 4.0 8.0 — sa/sec Symbol Unit Power Supply VPOR IDD IDD–STANDBY V mA mA Temperature–to–Bits Converter TERR CR °C Temperature Accuracy MC74A +25°C ≤ TA ≤ +85°C 0°C ≤ TA ≤ +125°C –40°C ≤ TA ≤ 0°C Conversion Rate (2) Serial Port Interface VIH Logic Input High 0.8 x VDD — — V VIL Logic Input Low — — 0.2 x VDD V VOL SDA Output Low IOL = 3 mA (3) IOL = 6 mA (3) — — — — 0.4 0.6 Input Capacitance SDA, SCL — 5.0 — CIN V pF ILEAK I/O Leakage –1.0 0.1 1.0 mA 1. Operating current is an average value integrated over multiple conversion cycles. Transient current may exceed this specification. 2. Maximum guaranteed conversion time after Power–On RESET (POR to DATA_RDY) is 250 msec. 3. Output current should be minimized for best temperature accuracy. Power dissipation within the MC74 will cause self–heating and temperature drift error. 4. SDA and SCL must be connected to VDD or GND. 5. VDD = 3.3V for MC74A5–33SNTR. VDD = 5.0V for MC74A5–50T. All part types of the MC74 will operate properly over the wider power supply range of 2.7V to 5.5V. 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. SERIAL PORT AC TIMING (VDD = 3.3 V or 5.0V, –40°C ≤ (TA = TJ) ≤ 125°C; CL = 80 pF unless otherwise noted.) Symbol Min Typ Max Unit fSMB SMBus Clock Frequency Characteristic 10 — 100 kHz tLOW Low Clock Period (10% to 10%) 4.7 — — msec tHIGH High Clock Period (90% to 90%) 4.0 — — msec tR SMBus Rise Time (10% to 90%) — — 1,000 nsec tF SMBus Fall Time (90% to 10%) — — 300 nsec tSU(START) Start Condition Setup Time (90% SCL to 10% SDA) (for Repeated Start Condition) 4.0 — — msec tH(START) Start Condition Hold Time 4.0 — — msec tSU–DATA Data in Setup Time 1,000 — — nsec tH–DATA Data in Hold Time 1,250 — — nsec tSU(STOP) Stop Condition Setup Time 4.0 — — msec tIDLE Bus Free Time Prior to New Transition 4.7 — — msec tPOR Power–On Reset Delay (VDD ≥ VPOR (Rising Edge)) — 500 — msec http://onsemi.com 3 MC74 DETAILED OPERATING DESCRIPTION MC74 Serial Bus Conventions The MC74 acquires and converts temperature information from its integrated solid state sensor with a basic accuracy of ±1°C . It stores the data in an internal register which is read through the serial port. The system interface is a slave SMBus. The temperature data can be read at any time through the SMBus port. Eight SMBus addresses are programmable for the MC74, which allows for a multi–sensor configuration. Also, there is low–power Standby mode where temperature acquisition is suspended. Term Transmitter The device sending data to the bus. Receiver Standby Mode The MC74 allows the host to put it into a low power (IDD = 5µA, typical) Standby mode. In this mode, the A/D converter is halted and the temperature data registers are frozen. The SMBus port operates normally. Standby mode is enabled by setting the SHDN bit in the CONFIG register. The table below summarizes this operation. Operating Mode 0 Normal 1 Standby SMBus Slave Address The MC74 is internally programmed to have a default SMBus address value of 1001 101b. Seven other addresses are available by custom order (contact factory). SERIAL PORT OPERATION The Serial Clock input (SCL) and bi–directional data port (SDA) form a 2–wire bi–directional serial port for programming and interrogating the MC74. The following conventions are used in this bus architecture: The device receiving data from the bus. Master The device which controls the bus: initiating transfers (START), generating the clock, and terminating transfers (STOP). Slave The device addressed by the master. Start A unique condition signaling the beginning of a transfer indicated by SDA falling (High — Low) while SCL is high. Stop A unique condition signaling the end of a transfer indicated by SDA rising (Low — High) while SCL is high. ACK A receiver acknowledges the receipt of each byte with this unique condition. The receiver drives SDA low during SCL high of the ACK clock–pulse. The Master provides the clock pulse for the ACK cycle. Busy Communication is not possible because the bus is in use. NOT Busy When the bus is idle, both SDA and SCL will remain high. Data Valid The state of SDA must remain stable during the High period of SCL in order for a data bit to be considered valid. SDA only changes state while SCL is low during normal data transfers (see Start and Stop conditions). Standby Mode Operation SHDN Bit Explanation All transfers take place under control of a host, usually a CPU or microcontroller, acting as the Master which provides the clock signal for all transfers. The MC74 always operates as a Slave. The serial protocol is illustrated in Figure 1. All data transfers have two phases; all bytes are transferred MSB first. Accesses are initiated by a start condition (START), followed by a device address byte and one or more data bytes. The device address byte includes a Read/Write selection bit. Each access must be terminated by a Stop Condition (STOP). A convention called Acknowledge (ACK) confirms receipt of each byte. Note that SDA can change only during periods when SCL is LOW (SDA changes while SCL is HIGH are reserved for Start and Stop Conditions). http://onsemi.com 4 MC74 Write Byte Format S ADDRESS 7 Bits WR ACK Slave Address ADDRESS 7 Bits WR ACK Command Byte: selects which register you are writing to. Read Byte Format S COMMAND 8 Bits ACK Slave Address COMMAND 8 Bits ACK S Command Byte: selects which register you are reading from. ADDRESS RD 7 Bits DATA 8 Bits ACK P Data Byte: data goes into the register set by the command byte. ACK Slave Address: repeated due to change in data– flow direction. DATA 8 Bits NACK P Data Byte: reads from the register set by the command byte. Receive Byte Format S ADDRESS RD 7 Bits ACK DATA 8 Bits NACK P Data Byte: reads data from the register commanded by the last Read Byte. S = Start Condition P = Stop Condition Shaded = Slave Transmission Figure 1. SMBus Protocols Start Condition (START) Acknowledge (ACK) The MC74 continuously monitors the SDA and SCL lines for a start condition (a HIGH to LOW transition of SDA while SCL is HIGH) and will not respond until this condition is met. Acknowledge (ACK) provides a positive handshake between the host and the MC74. The host releases SDA after transmitting eight bits, then generates a ninth clock cycle to allow the MC74 to pull the SDA line LOW to acknowledge that it successfully received the previous eight bits of data or address. Address Byte Immediately following the Start Condition, the host must transmit the address byte to the MC74. The states of A1 and A0 determine the 7–bit SMBus address for the MC74. The 7–bit address transmitted in the serial bit stream must match for the MC74 to respond with an Acknowledge (indicating the MC74 is on the bus and ready to accept data). The eighth bit in the Address Byte is a Read–Write Bit. This bit is a 1 for a read operation or 0 for a write operation. During the first phase of any transfer this bit will be set = 0 to indicate that the command byte is being written. Data Byte After a successful ACK of the address byte, the host must transmit the data byte to be written or clock out the data to be read. (See the appropriate timing diagrams. ) ACK will be generated after a successful write of a data byte into the MC74. Stop Condition (STOP) Communications must be terminated by a stop condition (a LOW to HIGH transition of SDA while SCL is HIGH). The Stop Condition must be communicated by the transmitter to the MC74. NOTE: Refer to Timing Diagrams for serial bus timing. http://onsemi.com 5 MC74 SMBUS Write Timing Diagram A B ILOW C IHIGH D E F G H I J K L M SCL SDA t SU(START) t H(START) t SU–DATA t H–DATA F = Acknowledge Bit Clocked into Master G = MSB of Data Clocked into Slave H = LSB of Data Clocked into Slave I = Slave Pulls SDA Line Low A = Start Condition B = MSB of Address Clocked into Slave C = LSB of Address Clocked into Slave D = R/W Bit Clocked into Slave E = Slave Pulls SDA Line Low t SU(STOP) t IDLE J = Acknowledge Clocked into Master K = Acknowledge Clock Pulse L = Stop Condition, Data Executed by Slave M= New Start Condition SMBUS Read Timing Diagram A B ILOW C IHIGH D E F G H I J K SCL SDA t SU(START) t H(START) t SU–DATA A = Start Condition B = MSB of Address Clocked into Slave C = LSB of Address Clocked into Slave D = R/W Bit Clocked into Slave t SU(STOP) E = 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 Figure 2. http://onsemi.com 6 t IDLE I = Acknowledge Clock Pulse J = Stop Condition K = New Start Condition MC74 REGISTER SET and PROGRAMMER’S MODEL Command Code Function Temperature Register (TEMP), 8–Bits, READ–ONLY The binary value (2’s complement format) in this register represents temperature of the integrated sensor following a conversion cycle. The registers are automatically updated in an alternating manner. RTR 00h Read Temperature (TEMP) Temperature Register (TEMP) RWCR 01h Read/Write Configuration (CONFIG) MC74 Command Set (SMBus READ_BYTE and WRITE_BYTE) Command Byte Description Configuration Register (CONFIG), 8–BITS, READ/WRITE D[6] SHDN Data Rdy Bit POR D[7] D[6] D[5]—D[0] D[5] D[4] D[3] D[2] D[1] D[0] Reserved Function Type Operation 0 STANDBY switch Read/ Write 1 = standby, 0 = normal 0 Data Ready* Read Only 1 = ready, 0 = not ready 0 Reserved — Always returns zero when read. N/A N/A DD DATA_RDY SHDN t conv D[5] D[4] D[3] D[2] D[1] D[0] MSB x x x x x x LSB Temperature–to–Digital Value Conversion (TEMP) *DATA_RDY bit reset at power–up and SHDN enable (see below). V D[6] In the temperature data registers, each unit value represents one degree (Celsius). The value is in 2’s–complement binary format such that a reading of 0000 0000b corresponds to 0°C. Examples of this temperature to binary value relationship are shown in the following table. Configuration Register (Config) D[7] D[7] t conv Figure 3. . DATA_RDY, SHDN Operation Logic Diagram ACTUAL TEMPERATURE REGISTERED TEMPERATURE BINARY HEX +130.00°C +127°C 0111 1111 +127.00°C +127°C 0111 1111 +126.50°C +127°C 0111 1111 +25.25°C +25°C 0001 1001 +0.50°C +1°C 0000 0001 +0.25°C 0°C 0000 0000 0.00°C 0°C 0000 0000 -0.25°C 0°C 0000 0000 -0.50°C 0°C 0000 0000 -0.75°C -1°C 1111 1111 -1.00°C -1°C 1111 1111 -25.00°C -25°C 1110 0111 -25.25°C -25°C 1110 0110 -54.75°C -55°C 1100 1001 -55.00°C -55°C 1100 1001 -65.00°C -65°C 1011 1111 Register Set Summary The MC74’s register set is summarized below. All registers are 8–bits wide. Name Description POR State Read TEMP Internal sensor temperature (2’s complement) 0000 0000b* √ CONFIG CONFIG register 0000 0000b √ Write √ *NOTE: The TEMP register immediately will be updated by the A/D converter after the DATA_RDY bit goes high. http://onsemi.com 7 MC74 TAPING FORM Component Taping Orientation for 5L SOT–23 Devices USER DIRECTION OF FEED DEVICE MARKING PIN 1 Standard Reel Component Orientation for TR Suffix Device (Mark Right Side Up) Tape & Reel Specifications Table Package Tape Width (W) Pitch (P) Part Per Full Reel Diameter 5L SOT–23 8 mm 4 mm 3000 7 inches MARKING SOT–23–5 1 2 3 4 MC74 Marking MC74A5–33SNTR V5 3 + 4 1 + 2 Date Code http://onsemi.com 8 MC74 PACKAGE DIMENSIONS SOT–23–5 SNTR SUFFIX PLASTIC PACKAGE CASE TBD ISSUE TBD 0.75 (1.90) REFERENCE .122 (3.10) .098 (2.50) .071 (1.80) .059 (1.50) .020 (0.50) .012 (0.30) .037 (0.95) REFERENCE .122 (3.10) .106 (2.70) .057 (1.45) .035 (0.90) 10 ° MAX. .006 (0.15) .000 (0.00) .010 (0.25) .004 (0.09) .022 (0.55) .008 (0.20) NOTE: SOT–23–5 is equivalent to EIAJ–SC74A Dimensions: inches (mm) http://onsemi.com 9 MC74 PACKAGE DIMENSIONS TO–220 T SUFFIX PLASTIC PACKAGE CASE TBD ISSUE TBD .113 (2.87) .103 (2.62) .185 (4.70) .165 (4.19) .410 (10.41) .390 (9.91) .156 (3.96) .146 (3.71) DIA. .055 (1.40) .045 (1.14) .258 (6.55) .230 (5.84) .594 (15.09) .569 (14.45) .037 (0.94) .027 (0.69) .560 (14.22) .518 (13.16) 3 _ – 7.5 _ 5 PLCS. .020 (0.51) .012 (0.30) .072 (1.83) .062 (1.57) .115 (2.92) .095 (2.41) .273 (6.93) .263 (6.68) Dimensions: inches (mm) http://onsemi.com 10 MC74 Notes http://onsemi.com 11 MC74 ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC (SCILLC). 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