tc74 tc74-4 3/26/99 ?2001 microchip technology inc. ds21462a tiny serial digital thermal sensor features digital temperature sensing in sot-23-5 package outputs temperature as an 8-bit digital word 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 3.0, and 5.5v operating range low power ................................... 200 a operating 5 a standby mode typical applications thermal protection for hard disk drives and other pc peripherals pc-card devices for notebook computers low-cost thermostat controls power supplies thermistor replacement general description the tc74 is a serially accessible digital temperature sensor particularly suited for low cost and small form-factor applications. temperature data is converted from the on- board thermal sensing element and made available as an 8-bit digital word. functional block diagram pin configuration ordering information part no. package address temp. range tc74a0-3.3vct sot-23a-5 1001 000 ?0 c to +125 c tc74a1-3.3vct sot-23a-5 1001 001 ?0 c to +125 c tc74a2-3.3vct sot-23a-5 1001 010 ?0 c to +125 c tc74a3-3.3vct sot-23a-5 1001 011 ?0 c to +125 c tc74a4-3.3vct sot-23a-5 1001 100 ?0 c to +125 c tc74a5-3.3vct* sot-23a-5 1001 101 ?0 c to +125 c tc74a6-3.3vct sot-23a-5 1001 110 ?0 c to +125 c tc74a7-3.3vct sot-23a-5 1001 111 ?0 c to +125 c tc74a0-5.0vct sot-23a-5 1001 000 ?0 c to +125 c tc74a1-5.0vct sot-23a-5 1001 001 ?0 c to +125 c tc74a2-5.0vct sot-23a-5 1001 010 ?0 c to +125 c tc74a3-5.0vct sot-23a-5 1001 011 ?0 c to +125 c tc74a4-5.0vct sot-23a-5 1001 100 ?0 c to +125 c tc74a5-5.0vct* sot-23a-5 1001 101 ?0 c to +125 c tc74a6-5.0vct sot-23a-5 1001 110 ?0 c to +125 c tc74a7-5.0vct sot-23a-5 1001 111 ?0 c to +125 c tc74a0-3.3vat to-220-5 1001 000 ?0 c to +125 c tc74a1-3.3vat to-220-5 1001 001 ?0 c to +125 c tc74a2-3.3vat to-220-5 1001 010 ?0 c to +125 c tc74a3-3.3vat to-220-5 1001 011 ?0 c to +125 c tc74a4-3.3vat to-220-5 1001 100 ?0 c to +125 c tc74a5-3.3vat to-220-5 1001 101 ?0 c to +125 c tc74a6-3.3vat to-220-5 1001 110 ?0 c to +125 c tc74a7-3.3vat to-220-5 1001 111 ?0 c to +125 c tc74a0-5.0vat to-220-5 1001 000 ?0 c to +125 c tc74a1-5.0vat to-220-5 1001 001 ?0 c to +125 c tc74a2-5.0vat to-220-5 1001 010 ?0 c to +125 c tc74a3-5.0vat to-220-5 1001 011 ?0 c to +125 c tc74a4-5.0vat to-220-5 1001 100 ?0 c to +125 c tc74a5-5.0vat to-220-5 1001 101 ?0 c to +125 c tc74a6-5.0vat to-220-5 1001 110 ?0 c to +125 c tc74a7-5.0vat to-220-5 1001 111 ?0 c to +125 c *default address. v dd gnd 1 2 nc 5 4 sda scl tc74 3 internal sensor (diode) ? modulator temperature register serial port interface control logic sda scl gnd v dd nc sda sclk 12345 tc74 communication with the tc74 is accomplished via a simple 2-wire smbus/i 2 c-compatible serial port. this bus also can be used to implement multi-drop/multi-zone moni- toring. the shdn bit in the config register can be used to activate the low-power standby mode. temperature resolution is 1 c. conversion rate is a nominal 8 samples/sec. power consumption is only 200 a (5 a standby). small size, low installed cost, and ease of use make the tc74 an ideal choice for implementing thermal manage- ment in a variety of systems. sot-23a-5 to-220-5
2 tc74-4 3/26/99 tiny serial digital thermal sensor tc74 ? 2001 microchip technology inc. ds21462a absolute maximum ratings* supply voltage (v dd ) ................................................. +6v voltage on any pin ............ (gnd 0.3v) to (v dd + 0.3v) operating temperature (t a ) ............................ see below storage temperature (t stg ) ................. 65 c to +150 c current on any pin ............................................... 50 ma package thermal resistance ( ja ) .................... 330 c/w *static-sensitive device. unused devices must be stored in conductive material. protect devices from static discharge and static fields. stresses above those listed under absolute maximum ratings may cause perma- nent damage to the device. these are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. notes: 1. operating current is an average value integrated over multiple conversion cycles. transient current may exceed this specifica tion. 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 tc74 will cause self-heating a nd temperature drift error. 4. sda and scl must be connected to v dd or gnd. 5. v dd = 3.3v for tc74x -3.3vct. v dd = 5.0v for tc74x -5.0vct. all part types of the tc74 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 v dd varies from the nominal value, accuracy will degrade 1 c/v of v dd change. electrical characteristics: v dd = 3.3v or 5.0v (note 5), 40 c t a 125 c, unless otherwise noted. symbol parameter test conditions min typ max unit power supply v por power-on reset threshold v dd falling edge or rising edge 1.2 2.2 v i dd operating current v dd = 5.5v 200 350 a serial port inactive (note 1) i dd-standby standby supply current v dd = 3.3v 510 a serial port inactive (note 4) temperature-to-bits converter t err temperature accuracy tc74a +25 c 3 tc74-4 3/26/99 tc74 tiny serial digital thermal sensor ? 2001 microchip technology inc. ds21462a smbus write timing diagram smbus read timing diagram timing diagrams t su(start) t h(start) t su-data t h-data t su(stop) t idle 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 a b cdef g h i j kl m 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 j = acknowledge clocked into master k = acknowledge clock pulse l = stop condition, data executed by slave m = new start condition i low i high scl sda t su(start) t h(start) t su-data t su(stop) t idle a = start condition b = msb of address clocked into slave c = lsb of address clocked into slave d = r/w bit clocked into slave a b cdef g h ij k 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 i low i high i = acknowledge clock pulse j = stop condition k = new start condition scl sda pin no. symbol type description 1 nc none not connected 2 gnd power system ground 3v dd power power supply input 4 scl input smbus serial clock 5 sda bi-directional smbus serial data pin description serial port ac timing: (v dd = 3.3v or 5.0v (note 5). 40 c (t a = t j ) 125 c; c l = 80 pf, unless otherwise noted.) symbol parameter test conditions min typ max unit t h-data data in hold time 1250 nsec t su(stop) stop condition setup time 4 sec t idle bus free time prior to new transition 4.7 sec t por power-on reset delay v dd v por (rising edge) 500 sec
4 tc74-4 3/26/99 tiny serial digital thermal sensor tc74 ? 2001 microchip technology inc. ds21462a detailed description scl input. smbus serial clock. clocks data into and out of the tc74. see system management bus specification rev. 1.0 for timing diagrams. 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. v dd input. power supply input. see electrical specifications. gnd input. ground return for all tc74 functions. functional description the tc74 acquires and converts temperature informa- tion from its on-board solid state sensor with a basic accu- racy 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 tc74, which allows for a multi-sensor configuration. also, there is low-power standby mode where temperature acquisition is suspended. standby mode the tc74 allows the host to put it into a low power (i dd = 5 a, 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. standby mode operation shdn bit operating mode 0 normal 1 standby smbus slave address the tc74 is internally programmed to have a default smbus address value of 1001 101b. seven other ad- dresses 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 program- ming and interrogating the tc74. the following conventions are used in this bus architecture: tc74 serial bus conventions term explanation transmitter the device sending data to the bus. receiver 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. ) 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 tc74 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 acknowl- edge (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).
5 tc74-4 3/26/99 tc74 tiny serial digital thermal sensor ? 2001 microchip technology inc. ds21462a figure 1. smbus protocols s address wr ack command ack data ack p 8 bits 7 bits 8 bits slave address command byte: selects which register you are writing to. data byte: data goes into the register set by the command byte. write byte format read byte format s address wr ack command ack s address rd ack data nack p 7 bits 8 bits 7 bits 8 bits slave address command byte: selects which register you are reading from. slave address: repeated due to change in data- flow direction. data byte: reads from the register set by the command byte. receive byte format s address rd ack data nack p 7 bits 8 bits data byte: reads data from the register commanded by the last read byte or write byte transmission. s = start condition p = stop condition shaded = slave transmission
6 tc74-4 3/26/99 tiny serial digital thermal sensor tc74 ? 2001 microchip technology inc. ds21462a start condition (start) the tc74 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. address byte immediately following the start condition, the host must transmit the address byte to the tc74. the states of a1 and a0 determine the 7-bit smbus address for the tc74. the 7-bit address transmitted in the serial bit stream must match for the tc74 to respond with an acknowledge (indicating the tc74 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. acknowledge (ack) acknowledge (ack) provides a positive handshake between the host and the tc74. the host releases sda after transmitting eight bits, then generates a ninth clock cycle to allow the tc74 to pull the sda line low to acknowledge that it successfully received the previous eight bits of data or address. 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 tc74. stop condition (stop) communications must be terminated by a stop condi- tion (a low to high transition of sda while scl is high). the stop condition must be communicated by the transmit- ter to the tc74. note: refer to timing diagrams for serial bus timing. register set and programmer? model tc74 command set (smbus read_byte and write_byte) command byte description command code function rtr 00h read temperature (temp) rwcr 01h read/write configuration (config) configuration register (config), 8-bits, read/write configuration register (config) d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] shdn data rdy reserved bit por function type operation d[7] 0 standby readwrite 1 = standby, switch 0 = normal d[6] 0 data ready* read only 1 = ready, 0 = not ready d[5]-d[0] 0 reserved - n/a n/a always returns zero when read. temperature register (temp), 8-bits, read-only the binary value (2 s complement format) in this regis- ter represents temperature of the on-board sensor following a conversion cycle. the registers are automatically updated in an alternating manner. temperature register (temp) d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] msb x x x x x x lsb *data_rdy bit reset at power-up and shdn enable (see below). figure 2. data_rdy, shdn operation logic diagram v dd data_rdy shdn t conv t conv
7 tc74-4 3/26/99 tc74 tiny serial digital thermal sensor ? 2001 microchip technology inc. ds21462a register set summary the tc74 s register set is summarized below. all regis- ters are 8-bits wide. name description por state read write temp internal sensor 0000 0000b* temperature (2 s complement) config config register 0000 0000b *note: the temp register will be immediately updated by the a/d converter after the data_rdy bit goes high. in the temperature data registers, each unit value repre- sents one degree (celsius). the value is in 2 s-complement binary format such that a reading of 0000 0000b corre- sponds to 0 c. examples of this temperature to binary value relationship are shown in the following table. temperature to digital value conversion (temp) actual registered binary temperature temperature 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 c0 c 0000 0000 0.00 c0 c 0000 0000 0.25 c0 c 0000 0000 0.50 c0 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 markings sot-23a-5 & = part number code + temperature range and voltage represents year and quarter code represents lot id number tc74 (v) code tc74a0-3.3vct v0 tc74a1-3.3vct v1 tc74a2-3.3vct v2 tc74a3-3.3vct v3 tc74a4-3.3vct v4 tc74a5-3.3vct v5 tc74a6-3.3vct v6 tc74a7-3.3vct v7 tc74a0-5.0vct u0 tc74a1-5.0vct u1 tc74a2-5.0vct u2 tc74a3-5.0vct u3 tc74a4-5.0vct u4 tc74a5-5.0vct u5 tc74a6-5.0vct u6 tc74a7-5.0vct u7
8 tc74-4 3/26/99 tiny serial digital thermal sensor tc74 ? 2001 microchip technology inc. ds21462a taping form package dimensions sot-23a-5 eiaj (sc-74a) .071 (1.80) .059 (1.50) .122 (3.10) .098 (2.50) 0.75 (1.90) reference .020 (0.50) .012 (0.30) .037 (0.95) reference .122 (3.10) .106 (2.70) .057 (1.45) .035 (0.90) .006 (0.15) .000 (0.00) .022 (0.55) .008 (0.20) 10 max. .010 (0.25) .004 (0.09) dimensions: inches (mm) user direction of feed user direction of feed device marking component taping orientation for 5-pin sot-23a (eiaj sc-74a) devices device marking pin 1 pin 1 standard reel component orientation tr suffix device (mark right side up) reverse reel component orientation rt suffix device (mark upside down) w p package carrier width (w) pitch (p) part per full reel reel size 5-pin sot-23a 8 mm 4 mm 3000 7 in carrier tape, number of components per reel and reel size
9 tc74-4 3/26/99 tc74 tiny serial digital thermal sensor ? 2001 microchip technology inc. ds21462a package dimensions 5-pin to-220 .273 (6.93) .263 (6.68) .037 (0.95) .025 (0.64) .117 (2.97) .103 (2.62) .415 (10.54) .390 (9.91) .156 (3.96) .140 (3.56) dia. .293 (7.44) .204 (5.18) .590 (14.99) .482 (12.24) .072 (1.83) .062 (1.57) pin 1 .185 (4.70) .165 (4.19) .055 (1.40) .045 (1.14) .613 (15.57) .569 (14.45) .115 (2.92) .087 (2.21) .025 (0.64) .012 (0.30) 3 - 7.5 5 plcs. dimensions: inches (mm)
10 tc74-4 3/26/99 tiny serial digital thermal sensor tc74 ? 2001 microchip technology inc. ds21462a information contained in this publication regarding device applications and the like is intended through suggestion only and ma y be superseded by updates. it is your responsibility to ensure that your application meets with your specifications. no representation or warrant y is given and no liability is assumed by microchip technology incorporated with respect to the accuracy or use of such information, or infringement of patent s or other intellectual property rights arising from such use or otherwise. use of microchip?s products as critical components in life support systems is not authori zed except with express written approval by microchip. no licenses are conveyed, implicitly or otherwise, except as maybe explicitly expressed herein, under any intellec- tual property rights. the microchip logo and name are registered trademarks of microchip technology inc. in the u.s.a. and othe r countries. all rights reserved. all other trademarks mentioned herein are the property of their respective companies. all rights reserved. ? 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