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? 2010 microchip technology inc. ds21935d-page 1 TCN75A features: temperature-to-digital converter accuracy: - 1 (typical) from -40c to +125c - 2c (maximum) from -40c to +125c user-selectable resolution: 0.5c to 0.0625c operating voltage range: 2.7v to 5.5v 2-wire interface: i 2 c? compatible operating current: 200 a (typical) shutdown current: 2 a (maximum) power-saving one-shot temperature measurement available packages: msop-8, soic-8 typical applications: personal computers and servers hard disk drives and other pc peripherals entertainment systems office equipment data communication equipment general purpose temperature monitoring typical application description: microchip technology inc.s TCN75A digital tempera- ture sensor converts temperatures between -40c and +125c to a digital word, with 1c (typical) accuracy. the TCN75A product comes with user-programmable registers that provide flexibility for temperature-sensing applications. the register settings allow user-selectable, 0.5c to 0.0625c temperature measurement resolution, configuration of the power-saving shutdown and one-shot (single conversion on command while in shutdown) modes and the specification of both temperature alert output and hysteresis limits. when the temperature changes beyond the specified limits, the TCN75A outputs an alert signal. the user has the option of setting the alert output signal polarity as an active-low or active-high comparator output for thermostat operation, or as temperature event interrupt output for microprocessor-based systems. this sensor has an industry standard 2-wire, i 2 c? compatible serial interface, allowing up to eight devices to be controlled in a single serial bus. these features make the TCN75A ideal for low-cost, sophisticated multi-zone temperature-monitoring applications. package types v dd r TCN75A sdascl i/o ports r pull-up pic ? 1 2 3 4 8 7 6 5 a0 v dd a1a2 sda gnd alert scl microcontroller alert v dd sda gnd alert scl 1 2 3 4 8 7 6 5 8-pin soic, msop a0 v dd a1a2 TCN75A 2-wire serial temperature sensor downloaded from: http:///
TCN75A ds21935d-page 2 ? 2010 microchip technology inc. notes: downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 3 TCN75A 1.0 electrical characteristics absolute maximum ratings ? v dd ....................................................................... 6.0v voltage at all input/output pins .....gnd C 0.3v to 5.5v storage temperature .......................... -65c to +150c ambient temp. with power applied ..... -55c to +125c junction temperature (t j ) ................................. 150c esd protection on all pins (hbm:mm) .......(4 kv:400v) latch-up current at each pin ......................... 200 ma ?notice: stresses above those listed under maximum ratings may cause permanent damage to the device. this is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this s pecification is not implied. exposure to maximum rating conditions for extended periods may affect device reliability. dc characteristics electrical specifications: unless otherwise indicated, v dd = 2.7v to 5.5v, gnd = ground, and t a = -40c to +125c. parameters sym min typ max unit conditions power supply operating voltage range v dd 2.7 5.5 v operating current i dd 200 500 a continuous operation shutdown current i shdn 0.1 2 a shutdown mode power-on reset (por) threshold v por 1 . 7 vv dd falling edge line regulation ? c/ ? v dd 0 . 2 c / v v dd = 2.7v to 5.5v temperature sensor accuracy t a = -40c to +125c t acy -2 1 +2 c v dd = 3.3v internal ?? adc conversion time: 0.5c resolution t conv 30 ms 33 samples/sec (typical) 0.25c resolution t conv 60 ms 17 samples/sec (typical) 0.125c resolution t conv 120 ms 8 samples/sec (typical) 0.0625c resolution t conv 240 ms 4 samples/sec (typical) alert output (open-drain) high-level current i oh 1 av oh = 5v low-level voltage v ol 0 . 4vi ol = 3 ma thermal response response time t res 1.4 s time to 63% (89c) 27c (air) to 125c (oil bath) downloaded from: http:///
TCN75A ds21935d-page 4 ? 2010 microchip technology inc. graphical symbol description digital input/output pin characteristics electrical specifications: unless otherwise indicated, v dd = 2.7v to 5.5v, gnd = ground and t a = -40c to +125c. parameters sym min typ max units conditions serial input/output (scl, sda, a0, a1, a2) input high-level voltage v ih 0.7 v dd v low-level voltage v il 0 . 3 v dd v input current i in -1 +1 a output (sda) low-level voltage v ol 0 . 4vi ol = 3 ma high-level current i oh 1 av oh = 5v low-level current i ol 6m a v ol = 0.6v capacitance c in 1 0p f sda and scl inputs hysteresis v hyst 0.05 v dd v v dd v ih v il i in voltage current time time v dd i oh voltage current time time input output v ol i ol temperature characteristics electrical specifications: unless otherwise indicated, v dd = +2.7v to +5.5v and gnd = ground. parameters sym min typ max units conditions temperature ranges specified temperature range t a -40 +125 c note 1 operating temperature range t a -40 +125 c storage temperature range t a -65 +150 c thermal package resistances thermal resistance, 8l-soic ? ja 1 6 3 c / w thermal resistance, 8l-msop ? ja 2 0 6 c / w note 1: operation in this range must not cause t j to exceed maximum junction temperature (+150c). downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 5 TCN75A timing diagram serial interface timing specifications ( note 1 ) electrical specifications: unless otherwise indicated, v dd = 2.7v to 5.5v, gnd = ground, t a = -40c to +125c, c l = 80 pf and all limits measured to 50% point. parameters sym min typ max units conditions 2-wire i 2 c? compatible interface serial port frequency f sc 0 400 khz clock period t sc 2.5 s low clock t low 1.3 s high clock t high 0.6 s rise time t r 20 300 ns 10% to 90% of v dd (scl, sda) fall time t f 20 300 ns 90% to 10% of v dd (scl, sda) data setup before scl high t su-data 0.1 s data hold after scl low t h-data 0 s start condition setup time t su-start 0.6 s start condition hold time t h-start 0.6 s stop condition setup time t su-stop 0.6 s bus idle t b-free 1.3 s note 1: specification limits are characterized but not product tested. t su-start t h -start t su - d a ta t su - s to p t b-free scl sda t h-data t h i g h t low t r , t f start condition data transmission stop condition downloaded from: http:///
TCN75A ds21935d-page 6 ? 2010 microchip technology inc. notes: downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 7 TCN75A 2.0 typical performance curves note: unless otherwise noted: v dd = 2.7v to 5.5v. figure 2-1: average temperature accuracy vs. ambient temperature, v dd = 3.3v. figure 2-2: average temperature accuracy vs. ambient temperature. figure 2-3: average temperature accuracy vs. ambient temperature, v dd = 3.3v. figure 2-4: temperature accuracy histogram, t a = +25c. figure 2-5: supply current vs. ambient temperature. figure 2-6: shutdown current vs. ambient temperature. note: the graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. the performance characteristics listed herein are not tested or guaranteed. in some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -55 -35 -15 5 25 45 65 85 105 125 t a (c) temperature accuracy (c) 0.0625c resolution 160 devices v dd = 3.3v specification limits -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -55 -35 -15 5 25 45 65 85 105 125 t a (c) temperature accuracy (c) 0.0625c resolution 160 devices v dd = 2.7v v dd = 3.3v v dd = 5.5v v dd = 5.0v -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -55 -35 -15 5 25 45 65 85 105 125 t a (c) temperature accuracy (c) 0.125c 0.0625c 0.5c 0.25c v dd = 3.3v 160 devices resolution 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.00.5 1.0 1.5 2.0 2.5 3.0 temperature accuracy (c) occurrences t a = +25c v dd = 3.3v 5 lots 32 samples/lot 160 devices 50 100 150 200 250 300 350 400 -55 -35 -15 5 25 45 65 85 105 125 t a (c) i dd (a) v dd = 2.7v v dd = 3.3v v dd = 5.5v v dd = 5.0v 0 0.2 0.4 0.6 0.8 1 -55 -35 -15 5 25 45 65 85 105 125 t a (c ) i shdn (a) downloaded from: http:///
TCN75A ds21935d-page 8 ? 2010 microchip technology inc. note: unless otherwise noted: v dd = 2.7v to 5.5v. figure 2-7: alert and sda i ol vs. ambient temperature. figure 2-8: alert and sda output v ol vs. ambient temperature. figure 2-9: TCN75A thermal response vs. time. 6 12 18 24 30 36 42 48 -55 -35 -15 5 25 45 65 85 105 125 t a (c) alert and sda i ol (ma) v dd = 5.5v v dd = 3.3v v dd = 2.7v v ol = 0.6v 0 0.1 0.2 0.3 0.4 -55 -35 -15 5 25 45 65 85 105 125 t a (c) alert and sda v ol (v) v dd = 5.5v v dd = 3.3v v dd = 2.7v i ol = 3 ma 5 25 45 65 85 105 125 145 -202468101214161820 time (s) temperature data (c) soic average of 10 samples per package 27c (air) to 125c (oil bath) msop downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 9 TCN75A 3.0 pin description the descriptions of the pins are listed in tab l e 3 - 1 . table 3-1: pin function table 3.1 serial data pin (sda) sda is a bidirectional input/output pin, used to serially transmit data to and from the host controller. this pin requires a pull-up resistor to output data. 3.2 serial clock pin (scl) scl is a clock input pin. all communication and timing is relative to the signal on this pin. the clock is generated by the host controller on the bus. 3.3 power supply input (v dd ) v dd is the power pin. the operating voltage, as specified in the dc electrical specification table, is applied on this pin. 3.4 ground (gnd) gnd is the system ground pin. 3.5 alert output the TCN75As alert pin is an open-drain output. the device outputs an alert signal when the ambient temperature goes beyond the user-programmed temperature limit. 3.6 address pins (a2, a1, a0) a2, a1 and a0 are device or slave address input pins. the address pins are the least significant bits (lsb) of the device address bits. the most significant bits (msb) (a6, a5, a4, a3) are factory-set to < 1001 >. this is illustrated in tab l e 3 - 2 . msop, soic symbol function 1 sda bidirectional serial data 2 scl serial clock input 3 alert temperature alert output 4 gnd ground 5 a2 address select pin (bit 2) 6 a1 address select pin (bit 1) 7 a0 address select pin (bit 0) 8v dd power supply input table 3-2: slave address device a6 a5 a4 a3 a2 a1 a0 TCN75A 1001xxx note: user-selectable address is shown by x. downloaded from: http:///
TCN75A ds21935d-page 10 ? 2010 microchip technology inc. notes: downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 11 TCN75A 4.0 serial communication 4.1 2-wire smbus/standard mode i 2 c? protocol-compatible interface the TCN75A serial clock input (scl) and the bidirectional serial data line (sda) form a 2-wire bidirectional smbus/standard mode i 2 c compatible communication port (refer to the digital input/output pin characteristics table and serial interface timing specifications (note 1) table ). the following bus protocol has been defined: table 4-1: TCN75A serial bus protocol descriptions 4.1.1 data transfer data transfers are initiated by a start condition (start), followed by a 7-bit device address and a read/write bit. an acknowledge (ack) from the slave confirms the reception of each byte. each access must be terminated by a stop condition (stop). repeated communication is initiated after t b-free . this device does not support sequential register read/ write. each register needs to be addressed using the register pointer. this device supports the receive protocol. the register can be specified using the pointer for the initial read. each repeated read or receive begins with a start condition and address byte. the TCN75A retains the previously selected register. therefore, it outputs data from the previously specified register (repeated pointer specification is not necessary). 4.1.2 master/slave the bus is controlled by a master device (typically a microcontroller) that controls the bus access and generates the start and stop conditions. the TCN75A is a slave device and does not control other devices in the bus. both master and slave devices can operate as either transmitter or receiver. however, the master device determines which mode is activated. 4.1.3 start/stop condition a high-to-low transition of the sda line (while scl is high) is the start condition. all data transfers must be preceded by a start condition from the master. if a start condition is generated during data transfer, the TCN75A resets and accepts the new start condition. a low-to-high transition of the sda line (while scl is high) signifies a stop condition. if a stop condition is introduced during data transmission, the TCN75A releases the bus. all data transfers are ended by a stop condition from the master. 4.1.4 address byte following the start condition, the host must transmit an 8-bit address byte to the TCN75A. the address for the TCN75A temperature sensor is 1001,a2,a1,a0 in binary, where the a2, a1 and a0 bits are set externally by connecting the corresponding pins to v dd 1 or gnd 0 . the 7-bit address transmitted in the serial bit stream must match the selected address for the TCN75A to respond with an ack. bit 8 in the address byte is a read/write bit. setting this bit to 1 commands a read operation, while 0 commands a write operation (see figure 4-1 ). term description master the device that controls the serial bus, typically a microcontroller. slave the device addressed by the master, such as the TCN75A. transmitter device sending data to the bus. receiver device receiving data from the bus. start a unique signal from master to initiate serial interface with a slave. stop a unique signal from the master to terminate serial interface from a slave. read/write a read or write to the TCN75A registers. ack a receiver acknowledges (ack) the reception of each byte by polling the bus. nak a receiver not-acknowledges (nak) or releases the bus to show end-of-data (eod). busy communication is not possible because the bus is in use. not busy the bus is in the idle state, both sda and scl remain high. data valid sda must remain stable before scl becomes high in order for a data bit to be considered valid. during normal data transfers, sda only changes state while scl is low. downloaded from: http:///
TCN75A ds21935d-page 12 ? 2010 microchip technology inc. figure 4-1: device addressing. 4.1.5 data valid after the start condition, each bit of data in transmission needs to be settled for a time specified by t su-data before scl toggles from low-to-high (see ?serial interface timing specifications (note 1)? . 4.1.6 acknowledge (ack) each receiving device, when addressed, is obliged to generate an ack bit after the reception of each byte. the master device must generate an extra clock pulse for ack to be recognized. the acknowledging device pulls down the sda line for t su-data before the low-to-high transition of scl from the master. sda also needs to remain pulled down for t h-data after a high-to-low transition of scl. during read, the master must signal an end-of-data (eod) to the slave by not generating an ack bit (nak) once the last bit has been clocked out of the slave. in this case, the slave will leave the data line released to enable the master to generate the stop condition. 123456789 scl sda 10 01 a2 a1 a0 start address byte slave address r/w TCN75A response code address ac k downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 13 TCN75A 5.0 functional description the TCN75A temperature sensor consists of a band- gap type temperature sensor, a ?? analog-to-digital converter (adc), user-programmable registers and a 2-wire i 2 c protocol-compatible serial interface. figure 5-1: functional block diagram. 5.1 temperature sensor the TCN75A uses the difference in the base-emitter voltage of a transistor while its collector current is changed from ic 1 to ic 2 . with this method, the ? v be depends only on the ratio of the two currents and the ambient temperature, as shown in equation 5-1 . equation 5-1: 5.2 ?? analog-to-digital converter a sigma-delta adc is used to convert ? v be to a digital word that corresponds to the transistor temperature. the converter has an adjustable resolution from 0.5c (at 30 ms conversion time) to 0.0625c (at 240 ms conversion time). thus, it allows the user to make trade-offs between resolution and conversion time. refer to section 5.3.2 ?sensor configuration register (config)? and section 5.3.4.7 ? ?? adc resolution? for details. resolution 0.5c 0.25c 0.125c 0.0625c temperature t hyst t set register register register register pointer i 2 c? interface configuration register ?? adc band-gap temperature sensor one-shot shutdown fault queue alert polarity alert comp/int ? v be kt q ----- - ?? ?? ln ic 1 ic 2 ? ?? ? = where: t = temperature in kelvin ? v be = change in diode base-emitter voltage k = boltzmanns constant q = electron charge ic 1 and ic 2 = currents with n:1 ratio downloaded from: http:///
TCN75A ds21935d-page 14 ? 2010 microchip technology inc. 5.3 registers the TCN75A has four registers that are user-accessible. these registers are specified as the ambient temperature (t a ) register, the temperature limit-set (t set ) register, the temperature hysteresis (t hyst ) register and device configuration (config) register. the ambient temperature register is a read-only register and is used to access the ambient temperature data. the data from the adc is loaded in parallel in the register. the temperature limit-set and temperature hysteresis registers are read/write registers that provide user-programmable temperature limits. if the ambient temperature drifts beyond the programmed limits, the TCN75A outputs an alert signal using the alert pin (refer to section 5.3.4.3 ?alert output configuration? ). the device configuration register provides access for the user to configure the TCN75As various features. these registers are described in further detail in the following sections. the registers are accessed by sending register point- ers to the TCN75A using the serial interface. this is an 8-bit pointer. however, the two least significant bits (lsbs) are used as pointers and all other bits need to be cleared < 0 >. this device has additional registers that are reserved for test and calibration. if these registers are accessed, the device may not perform according to the specification. the pointer description is shown below. figure 5-2: register block diagram. alert output control logic alert output resolution temperature t hyst t set register register register configuration register one-shot shutdown fault queue alert polarity alert comp/int register 5-1: register pointer u-0 u-0 u-0 u-0 u-0 u-0 r/w-0 r/w-0 000000p 1p 0 bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 7-2 unimplemented: read as 0 bit 1-0 pointer bits 00 = temperature register (t a ) 01 = configuration register (config) 10 = temperature hysteresis register (t hyst ) 11 = temperature limit-set register (t set ) . downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 15 TCN75A table 5-1: bit assignment summary for all registers register pointer p1 p0 msb/ lsb bit assignment 76 5 43210 ambient temperature register (t a ) 0 0 msb sign 2 6 c 2 5 c 2 4 c 2 3 c 2 2 c 2 1 c 2 0 c lsb 2 -1 c 2 -2 c 2 -3 c 2 -4 c 0 0 0 0 sensor configuration register (config) 0 1 lsb one-shot resolution fault queue alert polarity comp/int shutdown temperature hysteresis register (t hyst ) 1 0 msb sign 2 6 c 2 5 c 2 4 c 2 3 c 2 2 c 2 1 c 2 0 c lsb 2 -1 c 0 0 0 0 0 0 0 temperature limit-set register (t set ) 1 1 msb sign 2 6 c 2 5 c 2 4 c 2 3 c 2 2 c 2 1 c 2 0 c lsb 2 -1 c 0 0 0 0 0 0 0 downloaded from: http:///
TCN75A ds21935d-page 16 ? 2010 microchip technology inc. 5.3.1 ambient temperature register (t a ) the TCN75A has a 16-bit read-only ambient temperature register that contains 9-bit to 12-bit temperature data. (0.5c to 0.0625c resolutions, respectively). this data is formatted in twos complement. the bit assignments, as well as the corresponding resolution, is shown in the register assignment below. the refresh rate of this register depends on the selected adc resolution. it takes 30 ms (typical) for 9-bit data and 240 ms (typical) for 12-bit data. since this register is double-buffered, the user can read the register while the TCN75A performs analog-to-digital conversion in the background. the decimal code to ambient temperature conversion is shown in equation 5-2 : equation 5-2: t a code 2 4 ? ? = where: t a = ambient temperature (c) code = TCN75A output in decimal register 5-2: ambient temperature register (t a ) ? address < 0000 0000 >b upper half: r-0 r-0 r-0 r-0 r-0 r-0 r-0 r-0 sign 2 6 c 2 5 c 2 4 c 2 3 c 2 2 c 2 1 c 2 0 c bit 15 bit 8 lower half: r-0 r-0 r-0 r-0 r-0 r-0 r-0 r-0 2 -1 c/bit 2 -2 c 2 -3 c 2 -4 c 0 0 0 0 bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown note 1: when the 0.5c, 0.25c or 0.125c resolutions are selected, bit 6, bit 7 or bit 8 will remain clear < 0 >, respectively. downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 17 TCN75A figure 5-3: timing diagram for reading +25.25c temperature from the t a register (see section 4.0 ?serial communication? ). sda ac k 1001 a t a pointer 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 1001 a msb data ac k na k s p 2 a 1 a 0 12345678 12345678 12345678 address byte lsb data r TCN75A TCN75A TCN75A master master w sda scl 000 00011 001 01000 000 note: it is not necessary to select the register pointer if it was set from the previous read/ write. (see section 4.1.1 ) downloaded from: http:///
TCN75A ds21935d-page 18 ? 2010 microchip technology inc. 5.3.2 sensor configuration register (config) the TCN75A has an 8-bit read/write configuration register that allows the user to select the different features. these features include shutdown, alert output select as comparator or interrupt output, alert output polarity, fault queue cycle, temperature measurement resolution and one-shot mode (single conversion while in shutdown). these functions are described in detail in the following sections. register 5-3: config uration register (config) ? address < 0000 0001 >b r/w-0 r/w-0 r/w-0 r/w-0 r/w-0 r/w-0 r/w-0 r/w-0 one-shot resolution fault queue alert polarity comp/int shutdown bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 7 one-shot bit 1 = enabled 0 = disabled (power-up default) bit 6-5 ?? adc resolution bits 00 = 9 bit or 0.5c (power-up default) 01 = 10 bit or 0.25c 10 = 11 bit or 0.125c 11 = 12 bit or 0.0625c bit 4-3 fault queue bits 00 = 1 (power-up default) 01 =2 10 =4 11 =6 bit 2 alert polarity bit 1 = active-high 0 = active-low (power-up default) bit 1 comp/int bit 1 = interrupt mode 0 = comparator mode (power-up default) bit 0 shutdown bit 1 = enable 0 = disable (power-up default) downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 19 TCN75A figure 5-4: timing diagram for writing and reading from the configuration register (see section 4.0 ?serial communication? ). sda ac k 1001 a config pointer 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 1001 a data na k s p 2 a 1 a 0 12345678 12345678 address byte r TCN75A TCN75A TCN75A w sda scl 001 01100 000 reading the config register. writing to the config register to change the resolution to 0.0625c < 0110 0000 >b. sda ac k 1001 a 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte w TCN75A TCN75A msb data ac k p 12345678 1 config pointer TCN75A 001 01100 000 note: it is not necessary to select the register pointer if it was set from the previous read/ write (see section 4.1.1 ). downloaded from: http:///
TCN75A ds21935d-page 20 ? 2010 microchip technology inc. 5.3.3 temperature hysteresis register (t hyst ) the TCN75A has a 16-bit read/write temperature hysteresis register that contains a 9-bit data in twos compliment format. this register is used to set a hysteresis for the t set limit. therefore, the data represents a minimum temperature limit. if the ambient temperature drifts below the specified limit, the TCN75A asserts an alert output (refer to section 5.3.4.3 ?alert output configuration? ). this register uses the nine most significant bits (msbs) and all other bits are dont cares. the power-up default value of t hyst register is 75c, or <0100 1011 0>b in binary. register 5-4: temperature hysteresis register (t hyst ) ? address < 0000 0010 >b upper half: r/w-0 r/w-1 r/w-0 r/w-0 r/w-1 r/w-0 r/w-1 r/w-1 sign 2 6 c 2 5 c 2 4 c 2 3 c 2 2 c 2 1 c 2 0 c bit 15 bit 8 lower half: r/w-0 r-0 r-0 r-0 r-0 r-0 r-0 r-0 2 -1 c 0 0 0 0 0 0 0 bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 21 TCN75A figure 5-5: timing diagram for writing and reading from the temperature hysteresis register (see section 4.0 ?serial communication? ). sda ac k 1001 a 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 1001 a msb data ac k na k s p 2 a 1 a 0 12345678 12345678 12345678 address byte lsb data r TCN75A TCN75A TCN75A master master w sda scl 010 01011 111 00000 000 reading the t hyst register. writing to the t hyst register to set the temperature hysteresis to 95c < 0101 1111 0000 0000 >b . sda ac k 1001 a 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte w TCN75A TCN75A msb data ac k ac k p 12345678 12345678 lsb data t hyst pointer TCN75A TCN75A 010 01011 111 00000 000 note: it is not necessary to select the register pointer if it was set from the previous read/ write (see section 4.1.1 ). t hyst pointer downloaded from: http:///
TCN75A ds21935d-page 22 ? 2010 microchip technology inc. 5.3.4 temperature limit-set register (t set ) the TCN75A has a 16-bit read/write temperature limit-set register (t set ) which contains a 9-bit data in twos compliment format. this data represents a maximum temperature limit. if the ambient temperature exceeds this specified limit, the TCN75A asserts an alert output. (refer to section 5.3.4.3 ?alert output configuration? ). this register uses the nine most significant bits (msbs) and all other bits are dont cares. the power-up default value of the t set register is 80c, or <0101 0000 0>b in binary. register 5-5: temperature limit-set register (t set ) ? address < 0000 0011 >b upper half: r/w-0 r/w-1 r/w-0 r/w-1 r/w-0 r/w-0 r/w-0 r/w-0 sign 2 6 c 2 5 c 2 4 c 2 3 c 2 2 c 2 1 c 2 0 c bit 15 bit 8 lower half: r/w-0 r-0 r-0 r-0 r-0 r-0 r-0 r-0 2 -1 c 0 0 0 0 0 0 0 bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 23 TCN75A figure 5-6: timing diagram for writing and reading from the temperature limit-set register (see section 4.0 ?serial communication? ). sda ac k 1001 a t set pointer 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 1001 a msb data ac k na k s p 2 a 1 a 0 12345678 12345678 12345678 address byte lsb data r TCN75A TCN75A TCN75A master master w sda scl 011 01011 010 00000 000 reading the t set register. writing to the t set register to set the temperature limit to 90c, < 0101 1010 0000 0000 >b sda ac k 1001 a 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte w TCN75A TCN75A msb data ac k ac k p 12345678 12345678 lsb data t set pointer TCN75A TCN75A 011 01011 010 00000 000 note: it is not necessary to select the register pointer if it was set from the previous read/ write. (see section 4.1.1 ) downloaded from: http:///
TCN75A ds21935d-page 24 ? 2010 microchip technology inc. 5.3.4.1 shutdown mode the shutdown mode disables all power-consuming activities (including temperature sampling operations) while leaving the serial interface active. the device consumes 2 a (maximum) in this mode. it remains in this mode until the configuration register is updated to enable continuous conversion or until power is recycled. in shutdown mode, the config, t a , t set and t hyst registers can be read or written to; however, the serial bus activity will increase the shutdown current. 5.3.4.2 one-shot mode the TCN75A can also be used in a one-shot mode that can be selected using bit 7 of the config register. the one-shot mode performs a single temperature measurement and returns to shutdown mode. this mode is especially useful for low-power applications where temperature is measured upon command from a controller. for example, a 9-bit t a in one-shot mode consumes 200 a (typical) for 30 ms and 0.1 a (typical) during shutdown. to access this feature, the device needs to initially be in shutdown mode. this is done by sending a byte to the config register with bit 0 set < 1 > and bit 7 cleared < 0 >. once the device is in shutdown mode, the config register needs to be written to again, with bit 0 and bit 7 set < 1 >. this begins the single conversion cycle of t conv , 30ms for 9-bit data. once the conversion is completed, t a is updated and bit 7 of the config register becomes cleared < 0 > by the TCN75A. table 5-2: shutdown and one-shot mode description 5.3.4.3 alert output configuration the alert output can be configured as either a comparator output or as interrupt output mode using bit 1 of the config register. the polarity can also be specified as an active-high or active-low using bit 2 of the config register. the following sections describe each output mode, while figure 5-7 gives a graphical description. 5.3.4.4 comparator mode in comparator mode, the alert output is asserted when t a is greater than t set . the pin remains active until t a is lower than t hyst . the comparator mode is useful for thermostat-type applications, such as turning on a cooling fan or triggering a system shutdown when the temperature exceeds a safe operating range. in comparator mode, if the device enters the shutdown mode with asserted alert output, the output remains active during shutdown. the device must be operating in continuous conversion, with t a below t hyst , for the alert output to be deasserted. 5.3.4.5 interrupt mode in interrupt mode, the alert output is asserted when t a is greater than t set . however, the output is deas- serted when the user performs a read from any register. this mode is designed for interrupt-driven, microcontroller-based systems. the microcontroller receiving the interrupt will have to acknowledge the interrupt by reading any register from the TCN75A. this will clear the interrupt and the alert pin will become deasserted. when t a drifts below t hyst , the TCN75A outputs another interrupt and the controller needs to read a register to deassert the alert output. shutting down the device will also reset, or deassert, the alert output. operational mode one-shot (bit 7) shutdown (bit 0) continuous conversion 00 shutdown 01 continuous conversion (one-shot is ignored) 10 one-shot ( note 1 ) 11 note 1: the shutdown command < 01 > needs to be programmed before sending a one-shot command < 11 >. t set t hyst alert alert comparator mode interrupt mode active-low active-low t a register read * see section 5.3.4.5 ?interrupt mode? * downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 25 TCN75A figure 5-7: alert output. 5.3.4.6 fault queue the fault queue feature can be used as a filter to lessen the probability of spurious activation of the alert pin. t a must remain above t set for the consecutive number of conversion cycles selected using the fault queue bits. bit 3 and bit 4 of the config register can be used to select up to six fault queue cycles. for example, if six fault queues are selected, t a must be greater than t set for six consecutive conversions before alert is asserted as a comparator or an inter- rupt output. this queue setting also applies for t hyst . i f six fault queues are selected, t a must remain below t hyst for six consecutive conversions before alert is deasserted (comparator mode) or before another interrupt is asserted (interrupt mode). 5.3.4.7 ?? adc resolution the TCN75A provides access to select the adc resolution from 9-bit to 12-bit (0.5c to 0.0625c resolution) using bit 6 and bit 5 of the config register. the user can gain better insight into the trends and characteristics of the ambient temperature by using a finer resolution. increasing the resolution also reduces the quantization error. figure 2-3 shows accuracy versus resolution. table 5-3 shows the t a register conversion time for the corresponding resolution. table 5-3: resolution and conversion time 5.4 summary of power-up condition the TCN75A has an internal power-on reset (por) circuit. if the power supply voltage v dd glitches down to the 1.7v (typical) threshold, the device resets the registers to the power-up default settings. table 5-4 shows the power-up default summary. table 5-4: power-up defaults at power-up, the TCN75A has an inherent 2 ms (typical) power-up delay before updating the registers with default values and start a conversion cycle. this delay reduces register corruption due to unsettled power. after power-up, it takes t conv for the TCN75A to update the t a register with valid temperature data. bits resolution t conv (typical) 90 . 5 3 0 m s 10 0.25 60 ms 11 0.125 120 ms 12 0.0625 240 ms register data (hex) power-up defaults t a 0000 0c t set a000 80c t hyst 9600 75c pointer 00 temperature register config 00 continuous conversion comparator mode active-low output fault queue 1 9-bit resolution downloaded from: http:///
TCN75A ds21935d-page 26 ? 2010 microchip technology inc. notes: downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 27 TCN75A 6.0 applications information 6.1 connecting to the serial bus the sda and scl serial interface are open-drain pins that require pull-up resistors. this configuration is shown in figure 6-1 . figure 6-1: pull-up resistors on serial interface. the TCN75A is designed to meet 0.4v (maximum) voltage drop at 3 ma of current. this allows the TCN75A to drive lower values of pull-up resistors and higher bus capacitance. in this application, all devices on the bus must meet the same pull-down current requirements. 6.2 typical application microchip provides several microcontroller product lines with master synchronous serial port modules (mssp) that include the i 2 c interface mode. this module implements all master and slave functions and simplifies the firmware development overhead. figure 6-2 shows a typical application using the pic16f737 as a master to control other microchip slave products, such as eeprom, fan speed controllers and the TCN75A temperature sensor connected to the bus. figure 6-2: multiple devices on i 2 c? bus. the alert output can be wire-ored with a number of other open-drain devices. in such applications, the output needs to be programmed as an active-low output. most systems will require pull-up resistors for this configuration. 6.3 layout considerations the TCN75A does not require any additional components besides the master controller in order to measure temperature. however, it is recommended that a decoupling capacitor of 0.1 f to 1 f be used between the v dd and gnd pins. a high-frequency ceramic capacitor is recommended. it is necessary for the capacitor to be located as close as possible to the power pins in order to provide effective noise protection. for applications where a switching regulator is used to power the sensor, it is recommended to add a 200 ? resistor in series to v dd to filter out the switcher noise from the sensor. it is also recommended to add the series resistor in applications where a linear regulator is used to step-down a switching regulator voltage to power the sensor. for example, if a linearly regulated 3.3v from a 5v switching regulator is used to power the sensor, add a 200 ? series resistor (refer to figure 6-3 ). figure 6-3: power-supply filter using a single resistor. 6.4 thermal considerations the TCN75A measures temperature by monitoring the voltage of a diode located in the die. a low-impedance thermal path between the die and the printed circuit board (pcb) is provided by the pins. therefore, the TCN75A effectively monitors the temperature of the pcb. however, the thermal path for the ambient air is not as efficient because the plastic device package functions as a thermal insulator. a potential for self-heating errors can exist if the TCN75A sda and scl communication lines are heavily loaded with pull-ups. typically, the self-heating error is negligible because of the relatively small current consumption of the TCN75A. however, in order to maximize the temperature accuracy, the sda and scl pins need to be lightly loaded. pic ? sdascl v dd r r mcu TCN75A sda scl pic16f737 microcontroller temperature sensor 24lc01 eeprom tc654 fan speed controller TCN75A v dd 200 ? TCN75A switching regulator 0.1f bypass v dd 200 ? TCN75A switching regulator 0.1f bypass regulator linear downloaded from: http:///
TCN75A ds21935d-page 28 ? 2010 microchip technology inc. notes: downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 29 TCN75A 7.0 packaging information 7.1 package marking information 8-lead soic (150 mil) example: xxxxxxxx xxxxyyww nnn TCN75Av oa ^^ 1018 256 8-lead msop example: xxxxx ywwnnn n75a/e 018256 legend: xx...x customer-specific information y year code (last digit of calendar year) yy year code (last 2 digits of calendar year) ww week code (week of january 1 is week 01) nnn alphanumeric traceability code pb-free jedec designator for matte tin (sn) * this package is pb-free. the pb-free jedec designator ( ) can be found on the outer packaging for this package. note : in the event the full microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for customer-specific information. 3 e 3 e 3 e downloaded from: http:///
TCN75A ds21935d-page 30 ? 2010 microchip technology inc. d n e e1 note 1 1 2 e b a a1 a2 c l1 l downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 31 TCN75A 8-lead plastic micro small outline package (ua) [msop] note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging downloaded from: http:///
TCN75A ds21935d-page 32 ? 2010 microchip technology inc. note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 33 TCN75A note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging downloaded from: http:///
TCN75A ds21935d-page 34 ? 2010 microchip technology inc. downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 35 TCN75A appendix a: revision history revision d (september 2010) the following is the list of modifications: 1. updated section 6.3 layout considerations. revision c (november 2006) the following is the list of modifications: 1. updated the accuracy specification limits. 2. numerous edits throughout the data sheet. 3. updated the package outline drawings. 4. added disclaimers to package outline drawings. 5. updated the package marking information for pb-free markings. revision b (may 2006) the following is the list of modifications: 1. revised product id system; added oa713 and ua713 packages. revision a (november 2007) original release of this document. downloaded from: http:///
TCN75A ds21935d-page 36 ? 2010 microchip technology inc. notes: downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 37 TCN75A product identification system to order or obtain information, e. g., on pricing or delivery, refer to the factory or the listed sales office . device: TCN75A: temperature sensor temperature range : v= -40 ? c to +125 ? c package: oa = plastic soic, (150 mil body), 8-lead oa713 = plastic soic, (150 mil body), 8-lead, tape and reel ua = plastic micro small outline (msop), 8-lead ua713 = plastic micro small outline (msop), 8-lead tape and reel part no. x /xx package temperature range device examples: a) TCN75Avoa: 8ld soic package. b) TCN75Avoa713: tape and reel, 8ld soic package. a) TCN75Avua: 8ld msop package. b) TCN75Avua713: tape and reel, 8ld msop package. downloaded from: http:///
TCN75A ds21935d-page 38 ? 2010 microchip technology inc. notes: downloaded from: http:///
? 2010 microchip technology inc. ds21935d-page 39 information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. it is your responsibility to ensure that your application meets with your specifications. microchip makes no representations or warranties of any kind whether express or implied, written or oral, statutory or otherwise, related to the information, including but not limited to its condition, quality, performance, merchantability or fitness for purpose . microchip disclaims all liability arising from this information and its use. use of microchip devices in life support and/or safety applications is entirely at the buyers risk, and the buyer agrees to defend, indemnify and hold harmless microchip from any and all damages, claims, suits, or expenses resulting from such use. no licenses are conveyed, implicitly or otherwise, under any microchip intellectual property rights. trademarks the microchip name and logo, the microchip logo, dspic, k ee l oq , k ee l oq logo, mplab, pic, picmicro, picstart, pic 32 logo, rfpic and uni/o are registered trademarks of microchip technology incorporated in the u.s.a. and other countries. filterlab, hampshire, hi-tech c, linear active thermistor, mxdev, mxlab, seeval and the embedded control solutions company are registered trademarks of microchip technology incorporated in the u.s.a. analog-for-the-digital age, appl ication maestro, codeguard, dspicdem, dspicdem.net, dspicworks, dsspeak, ecan, economonitor, fansense, hi-tide, in-circuit serial programming, icsp, mindi, miwi, mpasm, mplab certified logo, mplib, mplink, mtouch, omniscient code generation, picc, picc-18, picdem, picdem.net, pickit, pictail, real ice, rflab, select mode, total endurance, tsharc, uniwindriver, wiperlock and zena are trademarks of microchip tec hnology incorporated in the u.s.a. and other countries. sqtp is a service mark of microchip technology incorporated in the u.s.a. all other trademarks mentioned herein are property of their respective companies. ? 2010, microchip technology incorporated, printed in the u.s.a., all rights reserved. printed on recycled paper. isbn: 978-1-60932-565-7 note the following details of the code protection feature on microchip devices: microchip products meet the specification cont ained in their particular microchip data sheet. microchip believes that its family of products is one of the most secure families of its kind on the market today, when used i n the intended manner and under normal conditions. there are dishonest and possibly illegal methods used to breach the code protection feature. all of these methods, to our knowledge, require using the microchip products in a manner outside the operating specif ications contained in microchips data sheets. most likely, the person doing so is engaged in theft of intellectual property. microchip is willing to work with the customer who is concerned about the integrity of their code. neither microchip nor any other semiconduc tor manufacturer can guarantee the security of their code. code protection does not mean that we are guaranteeing the product as unbreakable. code protection is constantly evolving. we at microchip are co mmitted to continuously improvin g the code protection features of our products. attempts to break microchips code protection feature may be a violation of the digital millennium copyright act. if such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that act. microchip received iso/ts-16949:2002 certification for its worldwide headquarters, design and wafer fabrication facilities in chandler and tempe, arizona; gresham, oregon and design centers in california and india. the company?s quality system processes and procedures are for its pic ? mcus and dspic ? dscs, k ee l oq ? code hopping devices, serial eeproms, microperipherals, nonvolatile memory an d analog products. in addition, microchip?s quality system for the design and manufacture of development systems is iso 9001:2000 certified. downloaded from: http:///
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