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rev. d ad7414/ad7415 0.5 c accurate, 10-bit digital t emperature sensors in sot-23 information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781/329-4700 www.analog.com fax: 781/326-8703 ?2004 analog devices, inc. all rights reserved. features 10-bit temperature-to-digital converter temperature range: ?0 c to +125 c typical accuracy of 0.5 c at +40 c smbus/i 2 c -compatible serial interface 3 a power-down current temperature conversion time: 29 s typ space-saving 6-lead (ad7414) and 5-lead (ad7415) sot-23 packages pin selectable addressing via as overtemperature indicator (ad7414 only) smbus alert function (ad7414 only) 4 versions allow 8 i 2 c addresses (ad7414) 2 versions allow 6 i 2 c addresses (ad7415) applications hard disk drives personal computers electronic test equipment office equipment domestic appliances process control cellular phones functional block diagram sda scl v dd smbus/i 2 c interface 10-bit analog-digital converter band gap temperature sensor configuration register temperature value register ad7415 as gnd smbus/i 2 c interface as gnd sda scl configuration register t high setpoint register t low setpoint register setpoint comparator alert temperature value register 10-bit analog-digital converter band gap temperature sensor v dd ad7414 general description the ad7414/ad7415 is a complete temperature monitoring system in 6-lead and 5-lead sot-23 packages. it contains a band gap temperature sensor and a 10-bit adc to monitor and digitize the temperature reading to a resolution of 0.25 c. the ad7414/ad7415 provides a 2-wire serial interface that is compatible with smbus and i 2 c interfaces. the part comes in four versions: the ad7414/ad7415-0, ad7414/ad7415-1, ad7414-2, and ad7414-3. the ad7414/ad7415-0 and ad7414/ad7415-1 versions provide a choice of three different smbus addresses for each version. all four ad7414 versions give the possibility of eight different i 2 c addresses while the two ad7415 versions allow up to six i 2 c addresses to be used. the ad7414/ad7415? 2.7 v supply voltage, low supply cur rent, serial interface, and small package size make it ideal for a variety of applications, including personal computers, office equipment, cellular phones, and domestic appliances. in the ad7414, on-chip registers can be programmed with high and low temperature limits, and an open-drain overtemperature indicator output (alert) becomes active when a pro grammed limit is exceeded. a configuration register allows programming of the state of the alert output (active high or active low). this output can be used as an interrupt or as an smbus alert. purchase of licensed i 2 c components of analog devices or one of its subli censed associated companies conveys a license for the purchaser under the philips i 2 c patent rights to use these components in an i 2 c system, provided that the system conforms to the i 2 c standard specification as defined by philips. product highlights 1. the ad7414/ad7415 has an on-chip temperature sensor that allows an accurate measurement of the ambient temperature to be made. it is capable of 0.5 c temperature accuracy. 2. smbus/i 2 c-compatible serial interface with pin selectable choice of three addresses per version of the ad7414/ad7415, eight address options in total for the ad7414, and six in total for the ad7415. 3. supply voltage of 2.7 v to 5.5 v. 4. space-saving 5-lead and 6-lead sot-23 packages. 5. 10-bit temperature reading to 0.25 c resolution. 6. the ad7414 has an overtemperature indicator that can be software disabled. used as an interrupt of smbus alert. 7. one-shot and automatic temperature conversion rates.
rev. d e2e ad7414/ad7415especifications 1 (t a = t min to t max , v dd = 2.7 v to 5.5 v, unless otherwise noted.) parameter a version unit test conditions/comments temperature sensor and adc accuracy 2 0.5 c typ v dd = 3 v @ +40 c e0.87 to +0.82 3 c max v dd = 3 v @ +40 c 1.5 c max v dd = 3 v @ e40 c to +70 c 2.0 c max v dd = 3 v @ e40 c to +85 c 3.0 c max v dd = 3 v @ e40 c to +125 c 2.0 c typ v dd = 3 v @ e40 c to +125 c 1.87 3 c max v dd = 5.5 v @ +40 c 2.0 c typ v dd = 5.5 v @ e40 c to +85 c 3.0 c max v dd = 5.5 v @ e40 c to +85 c 3.0 c typ v dd = 5.5 v @ e40 c to +125 c resolution 10 bits update rate, t r 800 ms typ temperature conversion time 25 s typ power supplies supply current 4 peak supply current 5 1.2 ma typ current during conversion supply current e nonconverting 900 a max peak current between conversions inactive serial bus 6 normal mode @ 3 v 169 a typ supply current with serial bus inactive. part not normal mode @ 5 v 188 a typ converting and d7 of configuration register = 0. active serial bus 7 normal mode @ 3 v 180 a typ supply current with serial bus active. part not normal mode @ 5 v 214 a typ converting and d7 of configuration register = 0. shutdown mode 3 a max d7 of configuration register = 1. typical values are 0.04 a at 3 v and 0.5 a at 5 v. digital input input high voltage, v ih 2.4 v min input low voltage, v il 0.8 v max input current, i in 8 1 a max v in = 0 v to v dd input capacitance, c in 10 pf max all digital inputs digital output (open-drain) output high voltage, v oh 2.4 v min output low voltage, v ol 0.4 v max i ol = 1.6 ma output high current, i oh 1 a max v oh = 5 v output capacitance, c out 10 pf max typ = 3 pf alert output saturation voltage 0.8 v max i out = 4 ma ac electrical characteristics 9, 10 serial clock period, t 1 2.5 s min see figure 1 data in setup time to scl high, t 2 50 ns min see figure 1 data out stable after scl low, t 3 0 ns min see figure 1 sda low setup time to scl low (start condition), t 4 50 ns min see figure 1 sda high hold time after scl high (stop condition), t 5 50 ns min see figure 1 sda and scl fall time, t 6 90 ns max see figure 1 power-up time 4 s typ notes 1 temperature range as follows: a version = e40 c to +125 c. 2 accuracy specifications apply only to voltages listed under test conditions. see temperature accuracy vs. supply section for ty pical accuracy performance over the full v dd supply range. 3 100% production tested at 40 c to these limits. 4 these current values can be used to determine average power consumption at different one-shot conversion rates. average power c onsumption at the automatic conversion rate of 1.25 khz is 940 w. 5 this peak supply current is required for 29 s (the conversion time plus power-up time) out of every 800 s (the conversion rate). 6 these current values are derived by not issuing a stop condition at the end of a write or read, thus preventing the part from g oing into a conversion. 7 the current is derived assuming a 400 khz serial clock being active continuously. 8 on power-up, the initial input current, i in , on the as pin is typically 50 a. 9 the sda and scl timing is measured with the input filters turned on so as to meet the fast mode i 2 c specification. switching off the input filters improves the transfer rate but has a negative effect on the emc behavior of the part. 10 guaranteed by design. not tested in production. specifications subject to change without notice.
rev. d ad7414/ad7415 e3e pin function descriptions mnemonic description as logic input. address select input that selects one of three i 2 c addresses for the ad7414/ad7415 (see table i). recommend a pull-up or pull-down resistor of 1 k . gnd analog and digital ground v dd positive supply voltage, 2.7 v to 5.5 v sda digital i/o. serial bus bidirectional data. open- drain output. alert ad7414 digital output. overtemperature indicator becomes active when temperature exceeds t high . open-drain output. scl digital input. serial bus clock. absolute maximum ratings 1 v dd to gnd . . . . . . . . . . . . . . . . . . . . . . . . . . . e0.3 v to +7 v sda input voltage to gnd . . . . . . . . . . . . . . e0.3 v to +7 v sda output voltage to gnd . . . . . . . . . . . . . e0.3 v to +7 v scl input voltage to gnd . . . . . . . . . . . . . . e0.3 v to +7 v alert output voltage to gnd . . . . . . . . . . e0.3 v to +7 v operating temperature range . . . . . . . . . . e40 c to +125 c storage temperature range . . . . . . . . . . . . e65 c to +150 c junction temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 150 c 5-lead sot-23 (rj-5) power dissipation 2 . . . . . . . . . . . . . . . . . w max = (t jmax e t a 3 )/ ja thermal impedance 4 ja , junction-to-ambient (still air) . . . . . . . . . . . 240 c/w 6-lead sot-23 (rj-6) power dissipation 2 . . . . . . . . . . . . . . . . . w max = (t jmax e t a 3 )/ ja thermal impedance 4 ja , junction-to-ambient (still air) . . . . . . . . . . 190.4 c/w 8-lead msop (rm-8) power dissipation 2 . . . . . . . . . . . . . . . . . w max = (t jmax e t a 3 )/ ja thermal impedance 4 ja , junction-to-ambient (still air) . . . . . . . . . . 205.9 c/w jc , junction-to-case . . . . . . . . . . . . . . . . . . . . 43.74 c/w notes 1 stresses above those listed under absolute maximum ratings may cause perma- nent damage to the device. this is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2 values relate to package being used on a standard 2-layer pcb. 3 t a = ambient temperature. 4 junction-to-case resistance is applicable to components featuring a preferential flow direction, e.g., components mounted on a heat sink. junction-to-ambient resistance is more useful for air-cooled, pcb-mounted components. scl t 1 sda data in sda data out t 2 t 3 t 4 t 5 t 6 figure 1. diagram for serial bus timing pin configurations sot-23 as sda 1 6 v dd scl 34 gnd 2 ad7414 top view (not to scale) 5 alert msop scl v dd 45 nc nc 18 alert gnd 36 sda 2 7 as ad7414 top view (not to scale) nc = no connect sot-23 as sda 15 v dd scl 3 4 gnd 2 ad7415 top view (not to scale) table i. i 2 c address selection part number as pin i 2 c address ad7414-0 float 1001 000 ad7414-0 gnd 1001 001 ad7414-0 v dd 1001 010 ad7414-1 float 1001 100 ad7414-1 gnd 1001 101 ad7414-1 v dd 1001 110 ad7414-2 n/a 1001 011 ad7414-3 n/a 1001 111 ad7415-0 float 1001 000 ad7415-0 gnd 1001 001 ad7415-0 v dd 1001 010 ad7415-1 float 1001 100 ad7415-1 gnd 1001 101 ad7415-1 v dd 1001 110
rev. d e4e ad7414/ad7415 caution esd (electrostatic discharge) sensitive device. electrostatic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge without detection. although the ad7414/ad7415 features proprietary esd protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. therefore, proper esd precautions are recommended to avoid performance degradation or loss of functionality. ordering guide temperature typ temperature package package minimum model range error @ 3 v option description branding quantities/reel ad7414art-0reel7 e40 c to +125 c 2 c rt-6 6-lead sot-23 cha 3,000 ad7414art-0reel e40 c to +125 c 2 c rt-6 6-lead sot-23 cha 10,000 ad7414art-0500rl7 e40 c to +125 c 2 c rt-6 6-lead sot-23 cha 500 ad7414arm-0reel7 e40 c to +125 c 2 c rm-8 8-lead msop cha 3,000 ad7414arm-0reel e40 c to +125 c 2 c rm-8 8-lead msop cha 10,000 ad7414arm-0 e40 c to +125 c 2 c rm-8 8-lead msop cha ad7414art-1reel7 e40 c to +125 c 2 c rt-6 6-lead sot-23 chb 3,000 ad7414art-1reel e40 c to +125 c 2 c rt-6 6-lead sot-23 chb 10,000 ad7414art-1500rl7 e40 c to +125 c 2 c rt-6 6-lead sot-23 chb 500 ad7414arm-1reel7 e40 c to +125 c 2 c rm-8 8-lead msop chb 3,000 ad7414arm-1reel e40 c to +125 c 2 c rm-8 8-lead msop chb 10,000 ad7414arm-1 e40 c to +125 c 2 c rm-8 8-lead msop chb ad7414art-2reel7 e40 c to +125 c 2 c rt-6 6-lead sot-23 chc 3,000 ad7414art-2reel e40 c to +125 c 2 c rt-6 6-lead sot-23 chc 10,000 ad7414art-3reel7 e40 c to +125 c 2 c rt-6 6-lead sot-23 chd 3,000 ad7414art-3reel e40 c to +125 c 2 c rt-6 6-lead sot-23 chd 10,000 ad7415art-0reel7 e40 c to +125 c 2 c rt-5 5-lead sot-23 cga 3,000 ad7415art-0reel e40 c to +125 c 2 c rt-5 5-lead sot-23 cga 10,000 ad7415art-0500rl7 e40 c to +125 c 2 c rt-5 5-lead sot-23 cga 500 ad7415art-1reel7 e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 3,000 ad7415art-1reel e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 10,000 ad7415art-1500rl7 e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 500 ad7415artz-500rl7 * e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 500 ad7415artz-0reel * e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 500 ad7415artz-0reel7 * e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 500 ad7415artz-1500rl7 * e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 500 ad7415artz-1reel * e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 500 ad7415artz-1reel7 * e40 c to +125 c 2 c rt-5 5-lead sot-23 cgb 500 eval-ad7414/ad7415eb evaluation board * z = pb-free part.
rev. d ad7414/ad7415 e5e circuit information the ad7414/ad7415 is a standalone digital temperature sensor. the on-chip temperature sensor allows an accurate measurement of the ambient device temperature to be made. the 10-bit a/d converter converts the temperature measured into a twos com ple- ment format for storage in the temperature register. the a/d converter is made up of a conventional successive-approxim a tion converter based around a capacitor dac. the serial interface is i 2 c and smbus compatible. the ad7414/ad7415 requires a 2.7 v to 5.5 v power supply. the temperature sensor has a working m easurement range of e40 c to +125 c. functional description temperature measurement is initiated by a couple of methods. the first uses an internal clock countdown of 800 ms, and a conversion is performed. the internal oscillator is the only circuit that is powered up between conversions, and once it times out, every 800 ms, a wake-up signal is sent to power up the rest of the circuitry. a monostable is activated at the beginning of the wake-up signal to ensure that sufficient time is given to the power- up process. the monostable typically takes 4 s to time out. it then takes typically 25 s for each conversion to be completed. the new temperature value is loaded into the temperature value register and ready for reading by the i 2 c interface. a temperature measurement is also initiated every time the one-shot method is used. this method requires the user to write to the one-shot bit in the configuration register when a temperature measurement is needed. setting the one-shot bit to a 1 will start a temperature conversion directly after the write operation. the track-and-hold goes into hold approxi- mately 4 s (monostable timeout) after the stop condition and a conversion is then initiated. typically 25 s later, the conversion is complete and the temperature value register is loaded with a new temperature value. the measurement modes are compared with a high temperature limit, stored in an 8-bit read/write register. this is applicable only to the ad7414 since the ad7415 does not have an alert pin and subsequently does not have an overtemperature monitoring function. if the measurement is greater than the high limit, the alert pin is activated (if it has already been enabled in the configuration register). there are two ways to deactivate the alert pin again: when the alert reset bit in the configu ration register is set to a 1 by a write operation, and when the tempera- ture measured is less than the value in the t low register. this alert pin is compatible with the smbus s mbalert option. configuration functions consist of ? switching between normal operation and full power-down ? enabling or disabling the scl and sda filters ? enabling or disabling the alert function ? setting alert pin polarity c/ p sda scl alert as supply 2.7v to 5.5v gnd ad7414 v dd 10 f 0.1 f 1k figure 2. typical connection diagram measurement technique a common method of measuring temperature is to exploit the negative temperature coefficient of a diode, or the base-emitter voltage of a transistor, operated at constant current. unfortu- nately, this technique requires calibration to null the effect of the absolute value of v be , which varies from device to device. the technique used in the ad7414/ad7415 is to measure the change in v be when the device is operated at two different currents. this is given by vktqnn be = () 1 where: k is boltzmann?s constant. q is the charge on the electron (1.6 10 e19 coulombs). t is the absolute temperature in kelvins. n is the ratio of the two currents. to adc v out + v out e sensing transistor v dd i n i sensing transistor figure 3. temperature measurement technique f igure 3 shows the method the ad7414/ad7415 uses to measure the ambient device temperature. to measure v be , the sensor (substrate transistor) is switched between operating currents of i and n i . the resulting waveform is passed through a chopper- stabilized amplifier that performs the functions of amplification and rectification of the waveform to produce a dc voltage pro por- tional to v be . this voltage is measured by the adc to give a temperature output in 10-bit twos complement format.
rev. d e6e ad7414/ad7415 temperature data format the temperature resolution of the adc is 0.25 c, which corresponds to 1 lsb of the adc. the adc can theoretically measure a temperature span of 255 c; the practical lowest value is limited to e40 c due to the device maximum ratings. the a grade can measure a temperature range of e40 c to +125 c. (temperature data format is shown in table ii.) table ii. a grade temperature data format digital output temperature db9 . . . db0 e55 c 11 0010 0100 e50 c 11 0011 1000 e25 c 11 1001 1100 e0.25 c 11 1111 1111 0 c 00 0000 0000 +0.25 c 00 0000 0001 +10 c 00 0010 1000 +25 c 00 0110 0100 +50 c 00 1100 1000 +75 c 01 0010 1100 +100 c 01 1001 0000 +125 c 01 1111 0100 a grade temperature conversion formula: positive temperature adc code = 4 negative temperature adc code = () * e 512 4 * db9 is removed from the adc code. internal register structure the ad7414 has five internal registers as shown in figure 4. four are data registers and one is an address pointer register. address pointer register temperature value register configuration register t high register t low register sda scl d a t a serial bus interface figure 4. ad7414 register structure the ad7415 has three internal registers as shown in figure 5. two are data registers and one is an address pointer register. serial bus interface address pointer register temperature value register sda scl d a t a configuration register figure 5. ad7415 register structure each data register has an address pointed to by the address pointer register when communicating with it. the temperature value register is the only data register that is read-only. address pointer register the address pointer register is an 8-bit register that stores an address that points to one of the four data registers of the ad7414 and one of the two data registers of the ad7415. the first byte of every serial write operation to the ad7414/ad7415 is the address of one of the data registers, which is stored in the address pointer register, and selects the data register to which subsequent data bytes are written. only the 2 lsbs of this regis- ter are used to select a data register. table iii. address pointer register p7 p6 p5 p4 p3 p2 p1 p0 00000 0r egister select table iv. ad7414 register address p1 p0 registers 00t emperature value register (read-only) 01c onfiguration register (read/write) 10t high register (read/write) 11t low register (read/write) table v. ad7415 register address p1 p0 registers 00t emperature value register (read-only) 01c onfiguration register (read/write) table vi. ad7414 configuration register d7 d6 d5 d4 d3 d2 d1 d0 pd fltr alert alert alert one test en ee e
rev. d ad7414/ad7415 e7e configuration register (address 01h) the configuration register is an 8-bit read/write register that is used to set the operating modes of the ad7414/ad7415. in the ad7414, six of the msbs are used (d7 to d2) to set the oper ating modes (see table vii). d0 and d1 are used for factory settings and must have zeros written to them during normal operation. table vii. ad7414 configuration register setting d7 full power-down if = 1. d6 bypass sda and scl filtering if = 0. d5 disable alert if = 1. d4 alert is active low if d4 = 0, alert is active high if d4 = 1. d3 reset the alert pin if set to 1. the next temperature conversion will have the ability to activate the alert function. the bit status is not stored; thus this bit will be 0 if read. d2 initiate a temperature conversion if set to a 1. the bit status is not stored; thus this bit will be 0 if read. table viii. ad7415 configuration register d7 d6 d5 d4 d3 d2 d1 d0 pd fltr test mode one test shot mode 0 * 1 * 0s * 0s * 0s * * default settings at power-up. in the ad7415, only three of the bits are used (d7, d6, and d2) to set the operating modes (see table ix). d0, d1, and d3 to d5 are used for factory settings and must have zeros written to them during normal operation. table ix. ad7415 configuration register settings d7 full power-down if = 1. d6 bypass sda and scl filtering if = 0. d2 initiate a temperature conversion if set to a 1. the bit status is not stored; thus this bit will be 0 if read. if the ad7414/ad7415 is in power-down mode (d7 = 1), a temperature conversion can still be initiated by the one-shot operation. this involves a write operation to the configuration register and setting the one-shot bit to a 1 (d2 = 1), which will cause the ad7414/ad7415 to power up, perform a single conversion, and power down again. this is a very power effi cient mode. frame 1 serial bus address byte frame 2 address pointer register byte r/ w w w w
rev. d e8e ad7414/ad7415 temperature value register (address 00h) the temperature value register is a 10-bit read-only register that stores the temperature reading from the adc in twos complement format. two reads are necessary to read data from this register. table x shows the contents of the first byte to be read, while table xi and table xii show the contents of the second byte to be read from ad7414 and ad7415, respec- tively. in table xi, d3 to d5 of the second byte are used as flag bits and are obtained from other internal registers. they function as follows: alert_flag: the state of this bit is the same as that of the alert pin. t high _flag: this flag is set to a 1 when the temperature measured goes above the t high limit. it is reset when the second temperature byte (table xi) is read. if the temperature is still greater than the t high limit after the read operation, the flag will be set again. t low _flag: this flag is set to a 1 when the temperature measured goes below the t low limit. it is reset when the second temperature byte (table xi) is read. if the temperature is still less than the t low limit after the read opera tion, the flag will be set again. the full theoretical span of the adc is 255 c, but in practice the temperature measurement range is limited to the operating range of the device, e40 c to +125 c for a grade. table x. temperature value register (first read) d15 d14 d13 d12 d11 d10 d9 d8 msb b8 b 7b6b5b4b3b2 table xi. ad7414 temperature value register (second read) d7 d6 d5 d4 d3 d2 d1 d0 b1 lsb alert_ t high _t low _0 0 0 flag flag flag table xii. ad7415 temperature value register (second read) d7 d6 d5 d4 d3 d2 d1 d0 b1 lsb n/a n/a n/a n/a n/a n/a ad7414 t high register (address 02h) the t high register is an 8-bit read/write register that stores the upper limit that will activate the alert output. therefore, if the value in the temperature value register is greater than the value in the t high register, the alert pin is activated (that is, if alert is enabled in the configuration register). since it is an 8-bit register, the temperature resolution is 1 c. table xiii. t high register d7 d6 d5 d4 d3 d2 d1 d0 msb b6 b5 b4 b3 b2 b1 b0 ad7414 t low register (address 03h) the t low register is an 8-bit read/write register that stores the lower limit that will deactivate the alert output. therefore, if the value in the temperature value register is less than the value in the t low register, the alert pin is deactivated (that is, if alert is enabled in the configuration register). since it is an 8-bit register, the temperature resolution is 1 c. sda no ack. by master start by master frame 1 serial bus address byte frame 2 single data byte from ad7414/ad7415 ack. by ad7414/ad7415 191 9 d7 d6 d5 d4 d3 d2 d1 d0 r/ w w
rev. d ad7414/ad7415 e9e table xiv. t low register d7 d6 d5 d4 d3 d2 d1 d0 msb b6 b5 b4 b3 b2 b1 b0 ad7414/ad7415 serial interface control of the ad7414/ad7415 is carried out via the i 2 c- compatible serial bus. the ad7414/ad7415 is connected to this bus as a slave device, under the control of a master device, e.g., the processor. serial bus address like all i 2 c-compatible devices, the ad7414/ad7415 has a 7-bit serial address. the four msbs of this address for the ad7414/ ad7415 are set to 1001. the ad7414/ad7415 comes in four versions: ad7414/ad7415-0, ad7414/ad7415-1, ad7414-2, and ad7414-3. the first two versions have three different i 2 c addresses available, which are selected by either tying the as pin to gnd, to v dd , or letting the pin float (see table i). by giving different addresses for the four versions, up to eight ad7414s or six ad7415s can be connected to a single serial bus, or the addresses can be set to avoid conflicts with other devices on the bus. the serial bus protocol operates as follows: 1. the master initiates data transfer by establishing a start condition, defined as a high to low transition on the serial data line sda, while the serial clock line scl remains high. this indicates that an address/data stream will follow. all slave peripherals connected to the serial bus respond to the start condition and shift in the next eight bits, consisting of a 7-bit address (msb first) plus an r/ w w w w we e n wne w n w w w ene w e e e e e en e e e
rev. d e10e ad7414/ad7415 the host device can process the alert interrupt and simulta- neously access all smbus alert devices through the alert response address. only the device that pulled the alert low will acknowledge the ara (alert response address). if more than one device pulls the alert pin low, the highest priority (lowest address) device will win communication rights via stan- dard i 2 c arbitration during the slave address transfer. the alert output becomes active when the value in the temperature value register exceeds the value in the t high register. it is reset when a write operation to the configuration register sets d3 to a 1 or when the temperature falls below the value stored in the t low register. the alert output requires an external pull-up resistor. this can be connected to a voltage different from v dd provided the maximum voltage rating of the alert output pin is not ex ceeded. the value of the pull-up resistor depends on the application, but should be as large as possible to avoid excessive sink currents at the alert output, which can heat the chip and affect the temperature reading. power-on defaults the ad7414/ad7415 always powers up with the following defaults: address pointer register pointing to the temperature value register. t high register loaded with 7fh. t low register loaded with 80h. configuration register loaded with 40h. note that the ad7415 does not have any t high or t low registers. operating modes mode 1 this is the power-on default mode of the ad7414/ad7415. in this mode, the ad7414/ad7415 does a temperature conversion every 800 ms and then partially powers down until the next conversion occurs. if a one-shot operation (setting d2 of the configuration register to a 1) is performed between automatic conversions, a conversion is initiated right after the write operation. after this conversion, the part returns to performing a conversion every 800 ms. depending on where a serial port access occurs during a conver sion, that conversion might or might not be aborted. if the conversion is completed before the part recognizes a serial port access, the temperature register will be updated with the new conversion. if the conversion is completed after the part recognizes a serial port access, the internal logic will prevent the temperature register from being updated since corrupt data could be read. a temperature conversion can start anytime during a serial port access (other than a one-shot operation), but the result of that conversion will only be loaded into the temperature register if the serial port access is not active at the end of the conversion. mode 2 the only other mode in which the ad7414/ad7415 operates is the full power-down mode. this mode is usually used when temperature measurements are required at a very slow rate. the power consumption of the part can be greatly reduced in this mode by writing to the part to go to a full power-down. full power-down is initiated right after d7 of the configuration register is set to 1. when a temperature measurement is required, a write operation can be performed to power up the part and put it into one-shot mode (setting d2 of the configuration register to a 1). the power-up takes approximately 4 ms. the part then performs a conversion and is returned to full power-down. the temperature value can be read in the full power-down mode since the serial interface is still powered up. power vs. throughput the two modes of operation for the ad7414/ad7415 will pro- duce different power vs. throughput performances. mode 2 is the sleep mode of the part and it achieves the optimum power performance. mode 1 in this mode, continuous conversions are performed at a rate of approximately one every 800 ms. figure 10 shows the times and currents involved with this mode of operation for a 5 v supply. at 5 v, the current consumption for the part when converting is 1.1 ma typically and the quiescent current is 188 a typically. the conversion time of 25 s plus power-up time of typically 4 s contributes 199.3 nw to the overall power dissipation in the following way: 29 800 5 1 1 199 3 sms ma nw /.. () () = the contribution to the total power dissipated by the remaining time is 939.96 w. 799 97 800 5 1 1 199 3 ./ . . ms ms a w () () = ? thus the total power dissipated during each cycle is: 199 3 939 96 940 16 .. . nw w w += ? i dd time 1.1ma 188 a 800ms 29 s figure 10. mode 1 power dissipation mode 2 in this mode, the part is totally powered down. all circuitry except the serial interface is switched off. the most power effi cient way of operating in this mode is to use the one-shot method. w rite to the configuration register and set the one-shot bit to a 1. the part will power up in approximately 4 ms and then perform a conversion. once the conversion is finished, the device will power down again until the pd bit in the configuration register is set to a 0 or the one-shot bit is set to 1. figure 11 shows the same timing as figure 10 in mode 1; a one-shot is initiated every 800 ms. if we take the voltage supply to be 5 v, we can work out the power dissipation in the following way. the current consumption for the part when converting is 1.1 ma typically and the quiescent current is 800 na typically. the conversion time of 25 s plus the power-up time of typically 4 ms contributes 199.3 nw to the overall power dissipation in the following way: 29 800 5 1 1 199 3 s/ ms v . ma . nw () () = the contribution to the total power dissipated by the remaining time is 3.9 w. 799.971 ms/800 ms 5 v 800 na 3.9 mw () () = thus the total power dissipated during each cycle is: 199 3 3 9 940 16 .. . nw w w += ?
rev. d ad7414/ad7415 e11e i dd time 800ms 1.1ma 800na 29 s figure 11. mode 2 power dissipation mounting the ad7414/ad7415 the ad7414/ad7415 can be used for surface or air temperature sensing applications. if the device is cemented to a surface with thermally conductive adhesive, the die temperature will be within about 0.1 c of the surface temperature, due to the device?s low power consumption. care should be taken to insulate the back and leads of the device from the air if the ambient air tem perature is different from the surface temperature being measured. the ground pin provides the best thermal path to the die, so the temperature of the die will be close to that of the printed circuit ground track. care should be taken to ensure that this is in good thermal contact with the surface being measured. as with any ic, the ad7414/ad7415 and its associated wiring and circuits must be kept free from moisture to prevent leakage and corrosion, particularly in cold conditions where condensa- tion is more likely to occur. water-resistant varnishes and conformal coatings can be used for protection. t he small size of the ad7414/ad7415 packages allows them to be mounted inside sealed metal probes, which provide a safe environment for the device. supply decoupling the ad7414/ad7415 should at least be decoupled with a 0.1 f ceramic capacitor between v dd and gnd. this is particularly important if the ad7414/ad7415 is mounted remote from the power supply. temperature accuracy vs. supply the temperature accuracy specifications are guaranteed for voltage supplies of 3 v and 5.5 v only. figure 12 gives the typi- cal performance characteristics of a large sample of parts over the full voltage range of 2.7 v to 5.5 v. figure 13 gives the typical performance characteristics of one part over the full voltage range of 2.7 v to 5.5 v. supply voltage (v) 2.7 temperature error ( c) e4 4 5.5 e3 e2 e1 0 1 2 3 3.0 e40 c +40 c +85 c figure 12. typical temperature error vs. supply for large sample of parts supply voltage (v) 2.7 temperature error ( c) e4 4 5.5 e3 e2 e1 0 1 2 3 5.0 e40 c +40 c +85 c 3.3 figure 13. typical temperature error vs. supply for one part typical temperature error graph figure 14 shows the typical temperature error plots for one device with v dd at 3.3 v and at 5.5 v. temperature ( c) e40 temperature error ( c) e4 4 e3 e2 e1 0 1 2 3 010203 04050607080 90 e30 e20 e10 100 110 125 85 5.5v 3.3v figure 14. typical temperature error @ 3.3 v and 5.5 v figure 15 shows a histogram of the temperature error at ambient temperature (40 c) over approximately 6,000 units. figure 15 shows that over 70% of the ad7414/ad7415 devices tested have a temperature error within 0.3 c. 0 100 200 300 400 500 600 700 800 900 0.81 0 0.27 0.54 1.08 number of units ambient temperature = 40 c 1.08 0.54 0.81 0.27 temperature error ( c) figure 15. ambient temperature error @ 3 v
rev. d e12e ad7414/ad7415 6-lead small outline transistor package [sot-23] (rt-6) dimensions shown in millimeters 1 3 4 5 2 6 2.90 bsc 1.60 bsc 2.80 bsc 1.90 bsc 0.95 bsc 0.22 0.08 10 4 0 0.50 0.30 0.15 max 1.30 1.15 0.90 seating plane 1.45 max 0.60 0.45 0.30 pin 1 indicator compliant to jedec standards mo-178ab 8-lead mini small outline package [msop] (rm-8) dimensions shown in millimeters 0.80 0.60 0.40 8 0 85 4 1 4.90 bsc pin 1 0.65 bsc 3.00 bsc seating plane 0.15 0.00 0.38 0.22 1.10 max 3.00 bsc coplanarity 0.10 0.23 0.08 compliant to jedec standards mo-187aa 5-lead small outline transistor package [sot-23] (rt-5) dimensions shown in millimeters pin 1 1.60 bsc 2.80 bsc 1.90 bsc 0.95 bsc 1 3 4 5 2 0.22 0.08 10 5 0 0.50 0.30 0.15 max seating plane 1.45 max 1.30 1.15 0.90 2.90 bsc 0.60 0.45 0.30 compliant to jedec standards mo-178aa outline dimensions
rev. d ad7414/ad7415 e13e revision history location page 9/04?data sheet changed from rev. c to rev. d. changes to absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 updated ordering guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8/03?data sheet changed from rev. b to rev. c. change to temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . universal updated features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 updated specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 updated absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 updated ordering guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 updated circuit information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 updated temperature data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 updated temperature value register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 updated figure 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 updated outline dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 11/02?data sheet changed from rev. a to rev. b. changes to absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 10/02?data sheet changed from rev. 0 to rev. a. changes to specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 changes to pin function descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 changes to absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 ordering guide updated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 change to figure 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 added to typical temperature error graph section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 added figure 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 outline dimensions updated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
e14e
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