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| 1 of 22 special features ? digital thermometer measures temperatures from - 55c to +100c in typically 0.2s ? zero standby power ? 0.5c resolution, digital temperature reading is twos complement of c value ? access to internal counters allows increased reso lution through interpolation ? reduces control, address, data, and power to a single data contact ? 8- bit device - generated crc for data integrity ? 8- bit family code specifies ds1920 communications requirements to reader ? special command set allows user to skip r om section and perform temperature measurements simultaneously for all devices on the bus ? 2 bytes of eeprom to be used either as alarm triggers or user memory ? alarm search directly indicates which device senses alarming temperatures ordering information pa rt pin - package ds1920- f5+ f5 microcan + denotes a lead(pb) - free/rohs - compliant package. f5 microcan data ground 0.51 5.89 16.25 17.35 a0 10 000000fbc52b 1- wire ? ? ? common i button features ? unique, factory - lasered and tested 64 - bit registration number (8 - bit family code + 48- bit serial num ber + 8 - bit crc tester) assures absolute traceability because no two parts are alike ? multidrop controller for microlan ? digital identification and information by momentary contact ? chip - based data carrier compactly stores information ? data can be accessed whi le affixed to object ? economically communicates to bus master with a single digital signal at 16.3kbps ? standard 16mm diameter and 1 - wire ? protocol ensure compatibility with i button ? family ? button shape is self - aligning with cup - shaped probes ? durable stainles s steel case engraved with registration number withstands harsh environments ? easily affixed with self - stick adhesive backing, latched by its flange, or locked with a ring pressed onto its rim ? presence detector acknowledges when reader first applies voltage examples of accessories ds9096p self - stick ad hesive pad ds9101 multipurpose clip ds9093ra mounting lock ring ds9093f snap - in fob ds9092 i button probe all dimensions are shown in millimet ers. i button and 1 - wire are registered trademarks of maxim integrated products, inc. 19 - 4886; rev 8/09 ds1920 temperature i button downloaded from: http:///
ds1920 2 of 22 i button description the ds1920 temperature i button provides 9 - bit temperature readings, which indicate the temperature of the device. inform ation is sent to/from the ds1920 over a 1 - wire interface. power for reading, writing, and performing temperature conversions is derived from the data line i tself. because each ds1920 contains a unique silicon serial number, multiple ds1920s can exis t on the same 1 - wire bus. this allows for placing temperature sensors in many different places. appl ications where this feature is useful include hvac environmental controls, sensing temperatures inside buildi ngs, equipment or machinery, and in process monitoring and control. overview the block diagram of figure 1 shows the major components of the ds 1920. the ds1920 has three main data components: 1) 64 - bit lasered rom, 2) temperature sensor, and 3) nonvolatile temperature alar m triggers th and tl. the device der ives its power from the 1 - wire communication line by storing energy on an internal capacitor during periods of time when the signal line is high and continues to operate off this power source during the low times of the 1 - wire line until it returns high to replenish the parasite (capacitor) supply. communication to the ds1920 is via a 1 - wire port. with the 1 - wire port, the memory and control functions will not be available before the rom function protocol ha s been established. the master must first provid e one of five rom function commands: 1) read rom, 2) match rom, 3) searc h rom, 4) skip rom, or 5) alarm search. these commands operate on the 64 - bit lasered rom portion of each device and can single out a specific device if many are present on the 1 - wire l ine as well as indicate to the bus master how many and what types of devices are present. after a rom f unction sequence has been successfully executed, the memory and control functions are accessibl e and the master may then provide any one of the five memo ry and control function commands. one control function command instructs the ds1920 to perform a tem perature measurement. the result of this measurement will be placed in the ds1920s scratchpad memo ry, and may be read by issuing a memory function comman d, which reads the contents of the scratchpad memory. the temperature alarm triggers th and tl consist of 1 byte of eeprom each. if the alarm search com mand is not applied to the ds1920, these registers may be used as general - purpose user memory. writing t h and tl is done using a memory function command. read access to these registers is through t he scratchpad. all data is read and written least significant bit first. downloaded from: http:/// ds1920 3 of 22 ds1920 block diagram figure 1 parasite power the block diagram (figure 1) shows t he parasite - powered circuitry. this circuitry steals power whenever the data contact is high. data will provide sufficient power as long as the specified timing and voltage requirements are met (see the 1- wire bus system section). the advantage of parasite power is that no local power source is needed for remote sensing of temperature. in order for the ds1920 to be able to perform accurate temperature conversions , sufficient power must be provided over the data line when a temperature conversion is taki ng place. the ds1920 requires a current during conversion of up to 1ma, therefore, the data line will not have s ufficient drive due to the 5 k ? pullup resistor. this problem is particularly acute if several ds 1920s are on the same data line and attempting to convert simultaneously. the way to assure that the ds1920 has sufficient supply current is to provide a strong pullup on the data line whenever temperature conversion or copying to the eeprom is taki ng place. this may be accomplished by using a mosfet to connect the data line directly to the power supply as shown in figure 2. the data line must be switched over to the strong pullup wit hin 10 s maximum after issuing a command that involves copying to the eeprom or initiates a temperatu re conversion. downloaded from: http:/// ds1920 4 of 22 st rong pullup for supplying ds1920 during temperature conversion figure 2 operation measuring temperature the ds1920 measures temperatures through the use of an on - board proprietary temperature measurement technique. a block diagram of the temperature me asurement circuitry is shown in figure 3. the ds1920 measures temperature by counting the number of clock cycles t hat an oscillator with a low temperature coefficient goes through during a gate period determined by a high temperature coefficient oscillat or. the counter is preset with a base count that corresponds to - 55c. if the counter reaches 0 before the gate period is over, the temperature register, which is also preset to the - 55c value, is incremented, indicating that the temperature is higher tha n - 55c. at the same time, the counter is then preset with a value determined by the slo pe accumulator circuitry. the counter is then clocked again until it reaches 0. if the gate period is still not finished, then this process repeats. the slope accumulator compensates for the nonlinear behavior of the osci llators over temperature, yielding a high - resolution temperature measurement. this is done by changing the n umber of counts necessary for the counter to go through for each incremental degree in tempe rature. to obtain the desired resolution, therefore, both the value of the counter and the number of counts per degree c (the value of the slope accumulator) at a given temperature must be known. internally, this calculation is done inside the ds1920 to provide 0.5c r esolution. the temperature reading is provided in a 16 - bit, sign - extended twos complement reading. table 1 describes the exact relationship of output data to measured temperature. the data is trans mitted serially over the 1 - wire interface. the ds1920 can measure temperature over the range of - 55c to +100c in 0.5c increments. for fahrenheit usage, a lookup table or conversion factor must be used . note that temperature is represented in the ds1920 in terms of a 1/2c lsb, yielding the foll owing 9 - bit format: msb lsb 1 1 1 0 0 1 1 1 0 = -25c downloaded from: http:/// ds1920 5 of 22 the most significant (sign) bit is duplicated into all of the bi ts in the upper msb of the 2 - byte temperature register in memory. this sign - extension yields the 16 - bit temperature r eadings as shown in table 1. higher resolutions may be obtained by the following procedure. f irst, read the temperature, and truncate the 0.5c bit (the lsb) from the read value. this value is temp_re ad. the value left in the counter may then be read. thi s value is the count remaining (count_remain) after the gate period ha s ceased. the last value needed is the number of counts per degree c (count _per_c) at that temperature. the actual temperature may be then be calculated by the user using t he following f ormula: temperature = temp_read - 0.25 + c count_per_ in) count_rema - _c (count_per temperature measuring circuitry figure 3 temperature/data relationships table 1 temperature digital output (binary) digital output (hex) +100 c 00000000 11001000 00c8h +25 c 00000000 00110010 0032h +? c 00000000 00000001 0001h +0 c 00000000 00000000 0000h -? c 11111111 11111111 ffffh -25 c 11111111 11001110 ffceh -55 c 11111111 10010010 ff92h set/clear lsb downloaded from: http:/// ds1920 6 of 22 operation alarm signaling after the ds1920 has performed a temperature conversion, the temperature valu e is compared to the trigger values stored in th and tl. since these registers are 8 bits only, the 0.5c bit is ignored for comparison. the most significant bit of th or tl directly correspond s to the sign bit of the 16 - bit temperature register. if the result of a temperature measurement is hi gher than th or lower than tl, an alarm flag inside the device is set. this flag is updated with ever y temperature measurement. as long as the alarm flag is set, the ds1920 will respond to the alarm se arch command. this allows many ds1920s to be connected in parallel doing simultaneous temperature measuremen ts. if somewhere the temperature exceeds the limits, the alarming device(s) can be identified and read immediately without having to read nonalarmin g devices. 64 - bit lasered rom each ds1920 contains a unique rom code that is 64 bits long. the first 8 bits are a 1 - wire family code (ds1920 code is 10h). the next 48 bits are a unique serial number. the last 8 bits are a crc of the first 56 bits. (see figure 4.) the 64 - bit rom and rom function control section allow the ds1920 to operate as a 1 - wire device and follow the 1 - wire protocol detailed in the 1- wire bus system section. the memory and control functions of the ds1920 are not accessible until the r o m function protocol has been satisfied. this protocol is described in the rom function protocol flowchart (figure 5). the 1 - wire bus master must first provide one of five rom function commands: 1) read rom, 2) match rom, 3) search rom, 4) skip rom, or 5) a larm search. after a rom function sequence has been successfully executed, the functions specific to the ds1920 are accessible and the bus master may then provide any one of the five memory and control function commands. crc generation the ds1920 has an 8 - bit crc stored in the most significant byte of the 64 - bit rom. the bus master can compute a crc value from the first 56 bits of the 64 - bit rom and compare it to the value stored within the ds1920 to determine if the rom data has been received error - free b y the bus master. the equivalent polynomial function of this crc is: crc = x 8 + x 5 + x 4 + 1 the ds1920 also generates an 8 - bit crc value using the same polynomial function shown above and provides this value to the bus master to validate the transfer of data by tes. in each case where a crc is used for data transfer validation, the bus master must calculate a crc value using the polynomial function given above and compare the calculated value to either the 8 - bit crc value stored in the 64 - bit rom portion o f the ds1920 (for rom reads) or the 8 - bit crc value computed within the ds1920 (which is read as a 9th byte when the scratchpad is read). the comparison of c rc values and decision to continue with an operation are determined entirely by the bus master. th e re is no circuitry inside the ds1920 that prevents a command sequence from proceeding if the crc st ored in or calculated by the ds1920 does not match the value generated by the bus master. the 1 - wire crc can be generated using a polynomial generator consisting of a sh ift register and xor gates as shown in figure 6. additional information about the m axim 1- wire cyclic redundancy check is available in the book of i button standards . the shift register bits are first initialized to 0. for the rom section , starting with the least significant bit of the family code, 1 bit at a time is shifted in. after the 8th bit of t he family code has been entered, then the serial number is entered. after the 48th bit of the serial numb er has been entered, the shift registe r contains the crc value. shifting in the 8 bits of crc should return t he shift register to all 0s. downloaded from: http:/// ds1920 7 of 22 64 - bit lasered rom figure 4 8- bit crc code 48- bit serial number 8- bit family code (10h) msb lsb msb lsb msb lsb rom functions flowchart figure 5 downloaded from: http:/// ds1920 8 of 22 1- wire crc code figure 6 memory the ds1920s memory is organized as shown in figure 7. the memory consi sts of a scratchpad and 2 bytes of eeprom that store the high and low temperature triggers th and tl. the scratchpad helps insure data integrity when communicating over the 1 - wire bus. data is first written to the scratchpad where it can be read back. after the data has been verified, a copy scratchpad comma nd will transfer the data to the eeprom. this process ensures data integrity when modifying the memo ry. the scratchpad is organized as 8 bytes of memory. the first 2 bytes conta in the measured temperature information. the 3rd and 4th bytes are volatile copies of th and tl and ar e refres hed with every power - on reset. the next 2 bytes are not used; upon reading back, however, they will appear as all logic 1s. the 7th and 8th bytes are count registers, which may be used in obtaining hi gher temperature resolution (see the operationmeasuring temperature section). there is a 9th byte that may be read with a read scratchpad command. this byte is a cyclic redundancy check (crc) over all of the 8 previous bytes. this crc is impleme nted as described in the crc generation section. ds1920 memory map figure 7 scratchpad byte eeprom temperature lsb 0 temperature msb 1 th/user byte 1 2 th/user byte 1 tl/user byte 2 3 tl/user byte 2 reserved 4 reserved 5 count remain 6 count per c 7 crc 8 downloaded from: http:/// ds1920 9 of 22 1- wire bus system the 1 - wir e bus is a system that has a single bus master and one or more slaves. the ds 1920 behaves as a slave. the discussion of this bus system is broken down into three t opics: hardware configuration, transaction sequence, and 1 - wire signaling (signal types and t iming). hardware configuration the 1 - wire bus has only a single line by definition; it is important th at each device on the bus be able to drive it at the appropriate time. to facilitate this, each device attached to the 1 - wire bus must have open - drain or 3- state outputs. the 1 - wire port of the ds1920 (data contact) is open drain with an interna l circuit equivalent to that shown in figure 8. a multidrop bus consis ts of a 1 - wire bus with multiple slaves attached. the 1 - wire bus requires a pullup resistor of approximately 5k ? . the idle state for the 1- wire bus is high. if for any reason a transaction needs to be suspended, t he bus must be left in the idle state if the transaction is to resume. if this does not occur and the bu s is left low for more than 120 s, one or more of the devices on the bus will be reset. hardware configuration figure 8 transaction sequence the protocol for accessing the ds1920 via the 1 - wire port is as follows: ? initialization ? rom function command ? memory/control function comman d ? transaction/data initialization all transactions on the 1 - wire bus begin with an initialization sequence. the initialization sequence consists of a reset pulse transmitted by the bus master followed by presen ce pulse(s) transmitted by the slave(s). the presence pulse lets the bus master know that the ds1920 is on the bu s and is ready to operate. for more details, see the 1- wire signaling section. downloaded from: http:/// ds1920 10 of 22 rom function commands once the bus master has detected a presence pulse, it can issue one of the five r om f unction commands. all rom function commands are eight bits long. a list of these co mmands follows (see the flowchart in figure 5). read rom [33h] this command allows the bus master to read the ds1920s 8 - bit family code, unique 48 - bit serial number, and 8 - bit crc. this command can only be used if there is a single ds1920 on th e bus. if more than one slave is present on the bus, a data collision will occur when all slaves try to transmit at the same time (open drain will produce a wired - and result). match rom [55h] the match rom command, followed by a 64 - bit rom sequence, allows the bus master to address a specific ds1920 on a multidrop bus. only the ds1920 that exactly matches t he 64 - bit rom sequence will respond to the subsequent memory function command. all slaves that do not match the 64 - bit rom sequence will wait for a reset pulse. this command can be used with a si ngle or multiple devices on the bus. skip rom [cch] this command can save time in a single drop bus system by allowing the bus master to ac cess the memory functions without providing the 64 - bit rom code. if more than one slave is present on the bus and a read command is issued following the skip rom command, data coll ision will occur on the bus as multiple slaves transmit simultaneously (open - drain pulldowns will produce a wired - and result). the skip rom command is useful to address all ds1920s on the bus to do a temp erature conversion. since the ds1920 uses a special command set, other device types will not respon d to these commands. search rom [f0h] when a system is initially brought up, the bus master might not kno w the number of devices on the 1- wire bus or their 64 - bit rom codes. the search rom command allows the bus master to use a pro cess of elimination to identify the 64 - bit rom codes of all slave devices on the bus. the rom search process is the repetition of a simple, three - step routine: read a bit, read the complement of the bit, then write the desired value of that bit. the bus master performs this simple, th ree - step routine on eac h bit of the rom. after one complete pass, the bus master knows the contents of the rom in o ne device. the remaining number of devices and their rom codes may be identified by additiona l passes. refer to chapter 5 of the book of i button standards for a com prehensive discussion of a rom search, including an actual example. alarm search [ech] the flowchart of this command is identical to the search rom comma nd; however, the ds1920 will respond to this command only if an alarm condition has been enco untered a t the last temperature measurement. an alarm condition is defined as a temperature higher than th or lower than tl. the alarm condition remains set as long as the ds1920 is powered up or until an other temperature measurement reveals a nonalarming value. fo r alarming, the trigger values stored in eeprom are taken into account. if an alarm condition exists and the th or tl settings are ch anged, another temperature conversion should be done to validate any alarm conditions . downloaded from: http:/// ds1920 11 of 22 memory and control function command s the following command protocols are summarized in table 2, and by the f lowchart of figure 9. write scratchpad [4eh] this command writes to the scratchpad of the ds1920, starting at addres s 2. the next 2 bytes written will be saved in scratchpad memory, at address locations 2 and 3. writing may be terminated at any point by issuing a reset. however, if a reset occurs before both bytes have been compl etely sent, the contents of these bytes will be indeterminate. bytes 2 and 3 can be read and written; all ot her bytes are read only. read scratchpad [beh] this command reads the complete scratchpad. after the last byte of the scratch pad is read, the bus master will receive an 8 - bit crc of all scratchpad bytes. if not all locations are to be read, t he master ma y issue a reset to terminate reading at any time. copy scratchpad [48h] this command copies from the scratchpad into the eeprom of the ds192 0, storing the temperature trigger bytes in nonvolatile memory. the bus master has to enabl e a strong pullup for at least 10 ms immediately after issuing this command. convert temperature [44h] this command begins a temperature conversion. no further data is required . the bus master has to enable a strong pullup for 0.75 seconds immediately after issuing this comm and. recall [b8h] this command recalls the temperature trigger values stored in eeprom t o the scratchpad. this recall operation happens automatically upon power - up to the ds1920 as well, so valid data is available in the scratchpad as soon as the device has power applied. downloaded from: http:/// ds1920 12 of 22 memory and control functions flowchart figure 9 downloaded from: http:/// ds1920 13 of 22 memory and control functions flowchart (continued) figure 9 from figure 9 first part to figure 9 third part downloaded from: http:/// ds1920 14 of 22 memory and control functions flowchart (continued) figure 9 1- wire signaling the ds1920 requires strict protocols to ensure data integrity. the protocol consists of five types of signaling on one line: reset sequence with reset pulse and presence pulse, write 0, write 1, read data and strong pullup. all these signals except presence pulse are initiat ed by the bus mast er. the initialization sequence required to begin any communication wit h the ds1920 is shown in figure 10. a reset pulse followed by a presence pulse indicates the ds1920 is ready to accept a rom command. the bus master transmits (tx) a reset pulse (t rstl , minimum 480 s). the bus master then releases the line and goes into receive mode (rx). the 1 - wire bus is pulled to a high state via the pullup resistor. after detecting the rising edge on the 1 - wire line, the ds1920 waits (t pdh , 15 C60 s) and then transmits the presence pulse (t pdl , 60 C240 s). downloaded from: http:/// ds1920 15 of 22 read/write time slots the definitions of write and read time slots are illustrated in figure 1 1. all time slots are initiated by the master driving the data line low. the falling edge of the data line sy nchronizes the ds1920 to the master by triggering a delay circuit in the ds1920. during write time slots, t he delay circuit determines when the ds1920 will sample the data line. for a read data time slot, if a 0 is t o be transmitted, the delay circuit determines how l ong the ds1920 will hold the data line low overriding the 1 generated by the master. if the data bit is a 1, the ds1920 will leave the read data time slot unchanged . strong pullup to provide energy for a temperature conversion or for copying data fr om the scratchpad to the eeprom, a low - impedance pullup of the 1 - wire bus to 5v is required just after the corresponding command has been sent by the master. during temperature conversion or copying the scr atchpad, the bus master controls the transition from a s tate where the data line is idling high via the pullup resistor to a s tate where the data line is actively driven to 5v, providing a minimum of 1ma of current for each ds1920 doing temperature conversion. this low impedance pullup should be active fo r 0.75 seconds for temperature conversion or at least 10ms for copying to the scratchpad. after that, t he data line returns to an idle high state controlled by the pullup resistor. the low - impedance pullup does not affect other devices on the 1- wire bus. theref ore, it is possible to multidrop other 1 - wire devices with the ds1920. initialization procedure reset and presence pulses figure 10 480 s t rstl < ? 480 s t rsth < (includes recovery time) 15 s t pdh < 60 s 60 s t pdl < 240 s resistor master ds1920 * in order not to mask interrupt signaling by ot her devices on the 1 - wire bus, t rstl + t r should always be less than 960 s. downloaded from: http:/// ds1920 16 of 22 ds1920 memory and control function commands table 2 instruction description protocol 1- wire bus after issuing protocol notes temperature conversion commands convert temperature initiates temperature conversion 44h strong pullup 1 memory com mands read scratchpad reads bytes from scratchpad and reads crc byte. beh ds1920 17 of 22 read/write timing dia gram (continued) figure 11 write - 0 time slot 60 s t low0 < t slot < 120 s 1 s t rec < read - data time slot 60 s t slot < 120 s 1 s t lowr < 15 s 0 t release < 45 s 1 s t rec < t rdv = 15 s t su < 1 s resistor master ds1920 downloaded from: http:/// ds1920 18 of 22 memory function example table 3 example: bus master initiates temperature conversion, then reads temperatu re . master mode data (lsb first) comments tx reset reset pulse(480 C960 s) rx presence presence pulse tx 55h issue match rom command tx <64 - bit rom code> issue address for ds1920 tx 44h issue convert temperature command tx data line is held high for at least 0.75 seconds by bus master to allow conversion to complete. tx reset reset pul se rx presence presence pulse tx 55h issue match rom command tx <64 - bit rom code> issue address for ds1920 tx beh issue read scratchpad command. rx <9 data bytes> read entire scratchpad plus crc; the master now recalculates the crc of the eight data bytes received from the scratchpad, compares the crc calculated and the crc read. if they match, the master continues; if not, this read operation is repeated. tx reset reset pulse rx presence presence pulse, done downloaded from: http:/// ds1920 19 of 22 absolute maximum ratings voltage on any pin relative to ground - 0.5v to +7.0v operating temperature - 55c to +100c storage temperature - 55c to +100c this is a stress rating only and functional operation of the device at these or an y other conditions above those in dicated in the operation sections of this specification is not implied. exposure to abso lute maximum rating conditions for extended periods of time ma y affect device reliability. dc electrical conditions (t a = - 55c to +100c.) parameter symbol conditions min typ max units notes pullup voltage v pup i/o functions 2.8 5.0 6.0 v 1, 2 +1/2c accurate temperature conversions 4.3 6.0 v logic 1 v ih 2.2 v 2 logic 0 v il -0.3 0.8 v 2, 10 dc electrical characteristics (v pup = 4.3v to 6.0v, t a = - 55c t o +100c.) parameter symbol conditions min typ max units notes thermometer error t err 0 c to + 70 c 1/2 c 11 -55 c to +0 c and + 70 c to +100 c see typical curve 11 active current i dd 1000 1500 a 3,4 input load current i l 5 a output lo gic low at 4ma v ol 0.4 v 2 capacitance (t a = +25c) parameter symbol min typ max units notes i/o (1 - wire) c in/out 800 pf 9 ac electrical characteristics: temperature conversion and copy scratchpad (v pup = 4.3v to 6.0v, t a = - 55c to +100c.) par ameter symbol min typ max units notes temperature conversion t conv 0.2 0.75 seconds copy scratchpad t copy 10 ms 5 downloaded from: http:/// ds1920 20 of 22 ac electrical characteristics: 1 - wire interface (v pup = 2.8v to 6.0v, t a = - 55c to +100c.) parameter symbol min typ max units notes time slot t slot 60 120 s write 1 low time t low1 1 15 s write 0 low time t low0 60 120 s read data valid t rdv exactly 15 s release time t release 0 15 45 s read data setup t su 1 s 8 recovery time t rec 1 s reset time high t rsth 480 s reset time low t rstl 480 4800 s 6, 7 presence detect high t pdhigh 15 60 s presence detect low t pdlow 60 240 s notes: 1. temperature conversion will work with 2c accuracy down to v pup = 3.4v. 2. all voltages are referenced to ground. 3. i dd s pecified with low - impedance pullup to 5.0v. 4. active current refers to temperature conversion. 5. writing to eeprom consumes approximately 200 a. 6. t rstl may be up to 4800 s. with longer times, the result of temperature conversion may get lost . 7. the reset low time should be restricted to a maximum of 960 s, to allow interrupt signaling, otherwise it could mask or conceal interrupt pulses. 8. read data setup time refers to the time the host must pull the 1 - wire bus low to read a bit. data is guaranteed to be valid within 1 s of this falling edge and will remain valid for 14 s minimum (15 s total from falling edge on 1 - wire bus). 9. capacitance on the data contact could be 800pf when power is first appli ed. if a 5k ? resistor is used to pull up the data line to v cc , 5 s after power has been applied, the parasite capacitance will not affect normal communications. 10. under certain low - voltage conditions, v ilmax may have to be reduced to as much as 0.5v to always guarantee a presence pulse. 11. see the typical performance curve for specification limits outside the 0c to +70c range. thermometer error reflects sensor accuracy as tested during calibration. downloaded from: http:/// ds1920 21 of 22 typical performance curve ds1920 temperature i button true temperature ( c) error = reading - true temperature when co ld, the true temperature is typically colder than the temperature reading . package information for the latest package outline information and land patterns, go to www.maxim - ic.com/ packages . package type package code document no. f5 microcan ib+5ns 21-0266 downloaded from: http:/// ds1920 22 of 22 maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a max im product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408 - 737 - 7600 ? 200 9 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision date description pages changed 082906 in the common i button features , reworded the ul statement. 1 110806 extended the temperature conversion time from 0.5s to 0.75s maximum. 11, 15, 16, 18, 19 040108 removed f3 microcan drawing and ordering information; added lead - free ds1920 - f5+ and removed leaded package from the ordering information table. 1 8/09 c orrected the ordering information part information (added hyphen to the part number) . 1 removed the ul#913 bullet from the common i button features section. 1 downloaded from: http:/// |
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