general description the MAX6627/max6628 precise digital temperature sensors report the temperature of a remote sensor. the remote sensor is a diode-connected transistor, typically a low-cost, easily mounted 2n3904 npn type that replaces conventional thermistors or thermocouples. the MAX6627/max6628 can also measure the die tem- perature of other ics, such as microprocessors (?s) or microcontrollers (?s) that contain an on-chip, diode- connected transistor. remote accuracy is ?? when the temperature of the remote diode is between 0? and +125? and the tem- perature of the MAX6627/max6628 is +30?. the tem- perature is converted to a 12-bit + sign word with 0.0625? resolution. the architecture of the device is capable of interpreting data as high as +145? from the remote sensor. the MAX6627/max6628 tempera- ture should never exceed +125?. these sensors are 3-wire serial interface spi compat- ible, allowing the MAX6627/max6628 to be readily con- nected to a variety of ?s. the MAX6627/max6628 are read-only devices, simplifying their use in systems where only temperature data is required. two conversion rates are available, one that continu- ously converts data every 0.5s (MAX6627), and one that converts data every 8s (max6628). the slower ver- sion provides minimal power consumption under all operating conditions (30?, typ). either device can be read at any time and provide the data from the last con- version. both devices operate with supply voltages between +3.0v and +5.5v, are specified between -55? and +125?, and come in space-saving 8-pin sot23 and lead-free tdfn packages. applications hard disk drive smart battery packs automotive industrial control systems notebooks, pcs features ? accuracy 1c (max) from 0c t rj +125c, t a = +30c 2.4c (max) from -55c t rj +100c, 0c t a +70c ? 12-bit + sign, 0.0625c resolution ? low power consumption 30 a (typ) (max6628) 200 a (typ) (MAX6627) ? operating temperature range (-55c to +125c) ? measurement temperature range, remote junction (-55c to +145c) ? 0.5s (MAX6627) or 8s (max6628) conversion rate ? spi-compatible interface ? +3.0v to +5.5v supply range ? 8-pin sot23 and tdfn packages ? lead(pb)-free version available (tdfn package) MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface ________________________________________________________________ maxim integrated products 1 19-2032; rev 5; 6/11 ordering information part pin-package top mark MAX6627 mka#tg16 8 sot23 aeqd MAX6627mta+t 8 tdfn-ep* aut max6628 mta+t 8 tdfn-ep* auu spi is a trademark of motorola, inc. pin configurations appears at end of data sheet. sdo gnd sck c + 3v to + 5.5v MAX6627 max6628 cs dxp dxn 2200pf 0.1 f v cc typical operating circuit note: all devices are specified over the -55? to +125? oper- ating temperature range. #denotes a rohs-compliant device that may include lead(pb) that is exempt under the rohs requirements. + denotes a lead-free/rohs-compliant package. t = tape and reel. * ep = exposed pad. for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim's website at www.maxim-ic.com.
MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. (all voltages referenced to gnd.) v cc ...........................................................................-0.3v to +6v sdo, sck, dxp, cs ...................................-0.3v to (v cc + 0.3v) dxn .......................................................................-0.3v to +0.8v sdo pin current range ......................................-1ma to +50ma current into all other pins ..................................................10ma esd protection (human body model) .............................?000v continuous power dissipation (t a = +70?) sot23 (derate 9.7mw/? above +70?) .....................777mw tdfn (derate 18.5mw/? above +70?)................1481.5mw operating temperature range .........................-55? to +125? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? electrical characteristics (3.0v v cc 5.5v, -55? t a +125?, unless otherwise noted. typical values are at t a = +25?, v cc = +3.3v, unless otherwise noted.) parameter symbol conditions min typ max units temperature 0 c t rj +125 c, t a = +30 c, v cc = +3.3v -1.0 ?.5 ? -55 c t rj +100 c, 0 c t a +70 c, v cc = +3.3v -2.4 +2.4 -55 c t rj +145 c, 0 c t a +70 c, v cc = +3.3v -4.5 +4.5 accuracy (note 1) -55 c t rj +125 c, -55 c t a +125 c, v cc = +3.3v -5.5 +5.5 ? power-supply sensitivity 0.25 0.7 ?/v resolution 0.0625 ? MAX6627 0.5 ti m e betw een c onver si on s tar ts t sample max6628 8 s conversion time t conv 180 250 320 ms power supply supply voltage range v cc 3.0 5.5 v i sdo shutdown, v cc = +0.8v 5 i idle adc idle, cs = low 20 supply current, sck idle i conv adc converting 360 600 ? MAX6627 200 400 average operating current i cc max6628 30 50 ? power-on reset (por) threshold v cc , falling edge 1.6 v high level 80 100 120 current sourcing for diode low level 8 10 12 ?
MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface _______________________________________________________________________________________ 3 electrical characteristics (continued) (3.0v v cc 5.5v, -55? t a +125?, unless otherwise noted. typical values are at t a = +25?, v cc = +3.3v, unless otherwise noted.) parameter symbol conditions min typ max units logic inputs ( cs , sck) logic input low voltage v il 0.3 x v cc v logic input high voltage v ih 0.7 x v cc v input leakage current i leak v cs = v sck = gnd or v cc 1 a logic outputs (sdo) output low voltage v ol i sink = 1.6ma 0.4 output high voltage v oh i source = 1.6ma v cc - 0.4 v timing characteristics (note 2, figure 2) serial-clock frequency f scl 5 mhz sck pulse width high t ch 100 ns sck pulse width low t cl 100 ns cs fall to sck rise t css c load = 10pf 80 ns cs fall to output enable t dv c load = 10pf 80 ns cs rise to output disable t tr c load = 10pf 50 ns sck fall to output data valid t do c load = 10pf 80 ns note 1: t rj is the temperature of the remote junction. note 2: serial timing characteristics guaranteed by design.
MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface 4 _______________________________________________________________________________________ 0 50 100 150 200 250 300 3.0 4.0 3.5 4.5 5.0 5.5 average operating current vs. supply voltage MAX6627/8 toc01 supply voltage (v) average operating current ( a) MAX6627 max6628 -3 -2 -1 0 1 2 3 -55 -5 -30 20 45 70 95 120 145 temperature error vs. temperature MAX6627/8 toc02 temperature ( c) temperature error ( c) t a = +25 c t a = 0 c MAX6627 t a = +70 c 0.6 1.0 0.8 1.4 1.2 1.8 1.6 2.0 2.4 2.2 2.6 -55 -5 20 45 -30 70 95 120 145 power-on-reset threshold vs. temperature MAX6627/8 toc03 temperature ( c) power-on-reset threshold (v) typical operating characteristics (v cc = +3.3v, t a = +25 c, unless otherwise noted.) pin name function 1 gnd ground 2 dxn combined current sink and adc negative input for remote diode. dxn is normally biased to a diode voltage above ground. 3 dxp combined current source and adc positive input for remote diode. place a 2200pf capacitor between dxp and dxn for noise filtering. 4v cc supply voltage input. bypass with a 0.1? to gnd. 5 sck spi clock input 6 cs chip select input. pulling cs low initiates an idle state, but the spi interface is still enabled. a rising edge of cs initiates the next conversion. 7 sdo spi data output 8 n.c. no connect. internally not connected. can be connected to gnd for improved thermal conductivity. ?p exposed pad. internally connected to gnd. connect to a large ground plane to maximize thermal performance. not intended as an electrical connection point. pin description 10 100k 10m 1k 100 10k 1m 100m temperature error vs. power-supply noise frequency MAX6627/8 toc04 frequency (hz) temperature error ( c) 0 4 2 6 8 10 12 v in = square wave applied to v cc with no 0.1 f capacitor v in = 250mvp-p 0 25 50 75 100 125 -2 2 0 4 6 8 10 12 14 response to thermal shock MAX6627/8 toc05 time (s) temperature ( c) 0 1 3 2 4 5 MAX6627/8 toc06 capacitance (pf) temperature error ( c) 0 10,000 5000 15,000 20,000 temperature error vs. dxp/dxn capacitance
MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface _______________________________________________________________________________________ 5 detailed description the MAX6627/max6628 remote digital thermometers report the temperature of a remote sensor. the remote sensor is a diode-connected transistor?ypically, a low-cost, easily mounted 2n3904 npn type?hat replaces conventional thermistors or thermocouples. the MAX6627/max6628 can also measure the die tem- perature of other ics, such as ?s or ?s, that contain an on-chip, diode-connected transistor. remote accuracy is ?? when the temperature of the remote diode is between 0? and +125? and the tem- perature of the MAX6627/max6628 is +30?. data is available as a 12-bit + sign word with 0.0625? resolu- tion. the operating range of the device extends from -55? to +125?, although the architecture of the device is capable of interpreting data up to +145?. the device itself should never exceed +125?. the MAX6627/max6628 are designed to work in con- junction with an external ? or other intelligent device serving as the master in thermostatic, process-control, or monitoring applications. the ? is typically a power management or keyboard controller, generating spi serial commands by ?it-banging?gpio pins. two conversion rates are available; the MAX6627 con- tinuously converts data every 0.5s, and the max6628 continuously converts data every 8s. either device can be read at any time and provide the data from the last conversion. the slower version provides minimal power consumption under all operating conditions. or, by tak- ing cs low, any conversion in progress is stopped, and the rising edge of cs always starts a fresh conversion and resets the interface. this permits triggering a con- version at any time so that the power consumption of the MAX6627 can be overcome, if needed. both devices operate with input voltages between +3.0v and +5.5v and are specified between -55? and +125?. the MAX6627/max6628 come in space-saving 8-pin sot23 and tdfn packages. adc conversion sequence the device powers up as a free-running data converter (figure 1). the cs pin can be used for conversion con- trol. the rising edge of cs resets the interface and starts a conversion. the falling edge of cs stops any conversion in progress, overriding the latency of the part. temperature data from the previous completed conversion is available for read (tables 1 and 2). it is required to maintain cs high for a minimum of 320ms to complete a conversion. idle mode pull cs low to enter idle mode. in idle mode, the adc is not converting. the serial interface is still active and temperature data from the last completed conversion can still be read. power-on reset the por supply voltage of the MAX6627/max6628 is typically 1.6v. below this supply voltage, the interface is inactive and the data register is set to the por state, figure 1. free-running conversion time and rate relationships MAX6627 max6628 0.5s sample rate 8s sample rate 0.25s conversion time adc converting adc idle d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 sign msb data lsb data low high-z high-z table 1. data output format
MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface 6 _______________________________________________________________________________________ 0?. when power is first applied and v cc rises above 1.6v (typ), the device starts to convert, although tem- perature reading is not recommended at v cc levels below 3.0v. serial interface figure 2 is the serial interface timing diagram. the data is latched into the shift register on the falling edge of the cs signal and then clocked out at the sdo pin on the falling edge of sck with the most-significant bit (msb) first. there are 16 edges of data per frame. the last 2 bits, d0 and d1, are always in high-impedance mode. the falling edge of cs stops any conversion in progress, and the rising edge of cs always starts a new conversion and resets the interface. it is required to maintain a 320ms minimum pulse width of high cs signal before a conversion starts. applications information remote-diode selection temperature accuracy depends upon having a good- quality, diode-connected, small-signal transistor. accuracy has been experimentally verified for all of the devices listed in table 3. the MAX6627/max6628 can also directly measure the die temperature of cpus and other ics with on-board temperature-sensing diodes. the transistor must be a small-signal type with a rela- tively high forward voltage. this ensures that the input voltage is within the a/d input voltage range. the for- ward voltage must be greater than 0.25v at 10? at the highest expected temperature. the forward voltage must be less than 0.95v at 100? at the lowest expect- ed temperature. the base resistance has to be less than 100 . tight specification of forward-current gain (+50 to +150, for example) indicates that the manufac- turer has good process control and that the devices have consistent characteristics. adc noise filtering the integrating adc has inherently good noise rejec- tion, especially of low-frequency signals such as 60hz/120hz power-supply hum. micropower operation places constraints on high-frequency noise rejection. lay out the pcb carefully with proper external noise fil- tering for high-accuracy remote measurements in elec- trically noisy environments. figure 2. spi timing diagram d15 d0 d1 d2 d3 sck sdo t dv t css t do cs t tr table 3. sot23-type remote-sensor transistor manufacturers manufacturer model central semiconductor (usa) cmpt3904 motorola (usa) mmbt3904 rohm semiconductor (japan) sst3904 siemens (germany) smbt3904 zetex (england) fmmt3904ct-nd note: transistors must be diode connected (short the base to the collector). table 2. temperature data format (twos complement) digital output (binary) temperature ( c) d15?3 d2 d1, d0 150 0,1001,0110,0000 0 xx 125 0,0111,1101,0000 0 xx 25 0,0001,1001,0000 0 xx 0.0625 0,0000,0000,0001 0 xx 0 0,0000,0000,0000 0 xx -0.0625 1,1111,1111,1111 0 xx -25 1,1110,0111,0000 0 xx -55 1,1100,1001,0000 0 xx
filter high-frequency electromagnetic interference (emi) at dxp and dxn with an external 2200pf capaci- tor connected between the two inputs. this capacitor can be increased to about 3300pf (max), including cable capacitance. a capacitance higher than 3300pf introduces errors due to the rise time of the switched- current source. pcb layout 1) place the MAX6627/max6628 as close as practical to the remote diode. in a noisy environment, such as a computer motherboard, this distance can be 4in to 8in, or more, as long as the worst noise sources (such as crts, clock generators, memory buses, and isa/pci buses) are avoided. 2) do not route the dxp/dxn lines next to the deflec- tion coils of a crt. also, do not route the traces across a fast memory bus, which can easily intro- duce +30? error, even with good filtering. otherwise, most noise sources are fairly benign. 3) route the dxp and dxn traces parallel and close to each other, away from any high-voltage traces such as +12vdc. avoid leakage currents from pcb cont- amination. a 20m leakage path from dxp to ground causes approximately +1? error. 4) connect guard traces to gnd on either side of the dxp/dxn traces (figure 3). with guard traces in place, routing near high-voltage traces is no longer an issue. 5) route as few vias and crossunders as possible to minimize copper/solder thermocouple effects. 6) when introducing a thermocouple, make sure that both the dxp and the dxn paths have matching thermocouples. in general, pcb-induced thermo- couples are not a serious problem. a copper solder thermocouple exhibits 3?/?, and it takes approxi- mately 200? of voltage error at dxp/dxn to cause a +1? measurement error, so most parasitic ther- mocouple errors are swamped out. 7) use wide traces. narrow traces are more inductive and tend to pick up radiated noise. the 10mil widths and spacings recommended in figure 3 are not absolutely necessary (as they offer only a minor improvement in leakage and noise), but use them where practical. 8) placing an electrically clean copper ground plane between the dxp/dxn traces and traces carrying high-frequency noise signals helps reduce emi. twisted pair and shielded cables for remote-sensor distances longer than 8in, or in par- ticularly noisy environments, a twisted pair is recom- mended. its practical length is 6ft to 12ft (typ) before noise becomes a problem, as tested in a noisy elec- tronics laboratory. for longer distances, the best solu- tion is a shielded twisted pair like that used for audio microphones. for example, belden #8451 works well for distances up to 100ft in a noisy environment. connect the twisted pair to dxp and dxn and the shield to ground, and leave the shield? remote end unterminated. excess capacitance at dxn or dxp limits practical remote-sensor distances (see typical operating characteristics ). for very long cable runs, the cable? parasitic capaci- tance often provides noise filtering, so the recommend- ed 2200pf capacitor can often be removed or reduced in value. cable resistance also affects remote-sensor accuracy. a 1 series resistance introduces about +1/2? error. MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface _______________________________________________________________________________________ 7 minimum 10mils 10mils 10mils 10mils gnd dxn dxp gnd figure 3. recommended dxp/dxn pc traces
MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface 8 _______________________________________________________________________________________ dxp dxn 12-bit + sign adc v cc spi interface sdo sck cs functional diagram sck v cc 1 2 8 7 n.c. sdo dxn dxp gnd sot23 top view 3 4 6 5 MAX6627 cs 1 + 34 865 n.c. cs sck MAX6627 max6628 2 7 sdo gnd dxp ep v cc dxn tdfn pin configurations chip information process: bicmos package information for the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages . note that a ?? ?? or ??in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package type package code outline no. land pattern no. 8 sot23 k8f#4 21-0078 90-0176 8 tdfn-ep t833+2 21-0137 90-0059
MAX6627/max6628 remote ?? accurate digital temperature sensors with spi-compatible serial interface maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it 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 _____________________ 9 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 4/01 initial release 1 7/01 removed future status from the max6628; changed i conv from 600a (max) to 650a (max) in the electrical characteristics table; replaced toc1 in the typical operating characteristics section 1, 2, 4 2 4/04 updated the lead temperature information in the absolute maximum ratings section; updated the notes for the electrical characteristics table 2, 3 3 4/06 added the tdfn package; updated table 3; removed transistor count from the chip information section 1, 2, 5, 6, 7, 8, 10 4 8/08 added missing exposed pad description, updated ordering part numbers, and updated pin name for pin 7 1C4, 6, 8C11 5 6/11 corrected the top mark information and sot23 part number in the ordering information table; added the soldering information to the absolute maximum ratings section; added the land pattern numbers to the package information table 1, 2, 8
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