general description the max6668/MAX6670 remote-junction thermal switches with an internal power transistor drive a cool- ing fan rated for supply voltages up to +12v and 250ma. these devices measure the temperature of an external p-n junction (typically a diode-connected tran- sistor) and turn on the fan power switch when the remote temperature rises above a factory-programmed threshold. self-contained and requiring no software development, the max6668/MAX6670 are simple ?rop-in?fan-control solutions for a variety of systems. the MAX6670 features an open-drain warn output that goes active when the remote temperature exceeds the factory-programmed fan activation threshold by +15?. the MAX6670 features an open-drain ot output that goes active when the remote temperature exceeds the factory-programmed threshold by +30?. the max6668/MAX6670 provide a fan-control input, forceon , that allows the fan to be driven externally, regardless of temperature. available temperature thresholds range from +40? to +75? in 5? increments. hysteresis is preset to 8? on the max6668 or pin selectable to 4?, 8?, or 12? using a three-level logic input on the MAX6670. temperature threshold accuracy is ?? (typ) and ?.2? (max) for remote-junction temperatures from +40? to +75?. the max6668/MAX6670 operate from a +3v to +3.6v power supply, and are specified over the automotive temperature range (-40? to +125?). the max6668 is offered in an 8-pin ?ax package and the MAX6670 is available in a space-saving 10-pin ?ax package. applications notebook and desktop computers network switches pc power supplies laboratory instruments card racks temperature alarms fan controls features +12v, 250ma integrated fan driver no calibration required pin-selectable 4?, 8?, or 12? hysteresis (MAX6670) factory-programmed temperature thresholds from +40? to +75? overtemperature warning signals 110? (typ) supply current space-saving 8-pin and 10-pin ?ax packages max6668/MAX6670 remote temperature switches with integrated fan controller/driver ________________________________________________________________ maxim integrated products 1 dxp gnd pgnd hyst v dd MAX6670 forceon fanout warn ot v dd dxn v dd c s 2200pf 2n3904 10k ? 10k ? 250ma fan +3.3v v dd +12v typical application circuit ordering information 19-2133; rev 2; 11/02 pin configuration appears at end of data sheet. typical operating circuit appears at end of data sheet. ordering information continued at end of data sheet. for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pi n - pa c k a g e t h r esh - o l d ( c ) max6668 aua40 -40 c to +125 c 8 max 40 max6668aua45 -40 c to +125 c 8 max 45 max6668aua50 -40 c to +125 c 8 max 50 max6668aua60 -40 c to +125 c 8 max 60 max6668aua70 -40 c to +125 c 8 max 70 max6668aua75 -40 c to +125 c 8 max 75
max6668/MAX6670 remote temperature switches with integrated fan controller/driver 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dd = +3v to +3.6v, t a = -40 c to +125 c, unless otherwise noted. typical values are at v dd = +3.3v and t a = +25 c.) 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. v dd to gnd ..............................................................-0.3v to +6v pgnd to gnd .......................................................-0.3v to +0.3v fanout to gnd ....................................................-0.3v to +15v dxn to gnd ..........................................................-0.3v to +0.8v dxp, warn , hyst, forceon , ot ...........-0.3v to (v dd + 0.3v) current into v dd , gnd, dxp, dxn, warn , hyst, forceon , ot ..............................................................20ma current into fanout , pgnd ........................................ 300ma continuous power dissipation (t a = +70 c) 8-pin max (derate 4.1mw/ c above +70 c) .............333mw 10-pin max (derate 5.6mw/ c above +70 c) ...........444mw operating temperature range .........................-40 c to +125 c storage temperature range .............................-60 c to +150 c junction temperature ......................................................+150 c lead temperature (soldering, 10s) .................................+300 c parameter symbol conditions min typ max units power supply power-supply range v dd 3 3.6 v average supply current i dd 110 200 a operating current during sampling 400 650 a power-on reset (por) threshold por v dd falling edge 1 1.5 2.0 v por threshold hysteresis 50 mv temperature sensor t rj = +40 c to +75 c (note 1), t a = 0 c to +85 c, v dd = +3.3v 1 2.2 fanout temperature threshold accuracy ? t th t rj = +40 c to +75 c (note 1), t a = -40 c to +125 c, v dd = +3.3v 1 4 c hyst = gnd 4 hyst = float 8 MAX6670 hyst = v dd 12 fanout temperature threshold hysteresis t hyst max6668 8 c warn temperature threshold (MAX6670 only) relative to fanout temperature threshold +15 c ot temperature threshold (MAX6670 only) relative to fanout temperature threshold +30 c supply sensitivity of temperature threshold 1 1.6 c/v temperature sample frequency 3.3 4 hz fan drive output fanout output voltage low v ol i sink = 250ma 0.5 1 v thermal shutdown 170 c thermal shutdown hysteresis 20 c logic input/output forceon input high voltage v ih 0.8 x v dd v
max6668/MAX6670 remote temperature switches with integrated fan controller/driver _______________________________________________________________________________________ 3 electrical characteristics (continued) (v dd = +3v to +3.6v, t a = -40 c to +125 c, unless otherwise noted. typical values are at v dd = +3.3v and t a = +25 c.) note 1: t rj is the temperature of the remote p-n junction. parameter symbol conditions min typ max units forceon input low voltage v il 0.2 x v dd v forceon input bias current v forceon = v dd or gnd 1 a warn , ot output voltage low v ol i sink = 6ma 0.5 v warn , ot output high leakage current i oh v warn or v ot = +5.5v 1 a typical operating characteristics (t a = +25 c, unless otherwise noted.) 0 0.2 0.1 0.4 0.3 0.6 0.5 0.7 0 100 150 50 200 250 300 fanout current vs. fanout voltage max6668/70 toc01 i fanout (ma) v fanout (v) t a = +25 c v dd = +3.3v 0 0.6 0.4 0.2 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.0 2.5 3.0 3.5 fanout voltage vs. supply voltage max6668/70 toc02 v dd (v) v fanout (v) t a = +105 c t a = +65 c t a = +25 c i fanout = 250ma 0 40 20 80 60 120 100 140 supply current vs. temperature max6668/70 toc03 temperature ( c) i dd ( a) 0 255075100 v dd = +3.3v, i fanout = 250ma 0 40 20 80 60 120 100 140 3.0 3.6 3.3 supply current vs. supply voltage max6668/70 toc04 v dd (v) i dd ( a) forceon = v dd 0 5 20 15 10 25 30 -1.00 -0.25 -0.50 0.50 -0.75 0 0.25 0.75 1.00 temperature threshold error max6668/70 toc05 threshold error ( c) percentage of samples (%) MAX6670aub040 119 samples
max6668/MAX6670 detailed description the max6668/MAX6670 are simple fan controllers/dri- vers that turn on an internal power transistor when the sensed temperature of an external p-n junction exceeds a factory-set threshold. by connecting a small (up to +12v/250ma nominal) cooling fan to fanout , a simple on/off fan-control system is created. do not con- nect the fan to a power supply of higher than 12v nomi- nal, 15v maximum. fanout driver and forceon controller fanout fan-driver output fanout is an open-drain output that sinks greater than 250ma of current to turn on the fan, either when the fan trip threshold is exceeded or the fan is forced on by dri- ving forceon low. forceon fan-control input drive forceon low to turn on the fan when the MAX6670 s remote-sensing junction temperature is less than the fan trip threshold temperature. this overrides the internal control circuitry and allows for an external device to activate the fan. overtemperature alarm outputs warn output (MAX6670 only) warn is an active-low, open-drain digital output that indicates when the external p-n junction s temperature exceeds 15 c above the fan trip threshold. the warn output serves as a warning that the system temperature has continued to rise well above the fan activation tem- perature. ot output (MAX6670 only) ot is an active-low, open-drain digital output that indi- cates when the external p-n junction s temperature exceeds 30 c above the fan trip threshold. ot serves as a thermal shutdown output to the system in case of excessive temperature rise. hysteresis input the temperature comparator has hysteresis to prevent small temperature changes near the threshold temper- ature from causing the fan to turn on and off repeatedly over short periods of time. the fanout pin goes active and powers the fan when the external p-n junc- tion s temperature exceeds the factory-programmed remote temperature switches with integrated fan controller/driver 4 _______________________________________________________________________________________ pin description pin max6668 MAX6670 name function 1 1 pgnd power ground. pgnd is the power ground for the fanout power mosfet switch. 25 forceon fan-control input. drive forceon high for normal operation. drive forceon low to force fan on. 3 3 dxp current source positive input. connect to the anode of the external diode- connected transistor. do not leave dxp floating. connect a 2200pf capacitor between dxp and dxn for noise filtering. 4 4 dxn current sink negative input. connect to the cathode of the external diode- connected transistor. dxn is internally biased to a diode voltage drop. 5, 7 7 gnd ground 68v dd positive power supply 810 fanout fan-drive output. fanout is an open-drain power mosfet that sinks up to 250ma current to turn on the fan when the sensed temperature exceeds the fan trip threshold or the fan is forced on by driving forceon low. 2 warn temperature warning output. warn is an open-drain output that goes low when the sensed junction temperature is 15 c higher than the fan trip threshold. 6 ot overtemperature output. ot is an open-drain output that goes low when the sensed junction temperature is 30 c higher than the fan trip threshold. 9 hyst hysteresis control input. hyst is a three-level logic input for controlling the fan- drive comparator s hysteresis. connect hyst to gnd for 4 c hysteresis, to v dd for 12 c hysteresis, or leave floating for 8 c hysteresis.
trip temperature. as the cooling fan operates, the cir- cuit board temperature should decrease, which causes the external p-n junction s temperature to decrease. when the p-n junction s temperature is equal to the trip threshold minus the hysteresis, the fanout pin turns the fan off, removing power from the fan. for the MAX6670, hyst is a three-level logic input for control- ling the fan-drive comparator s hysteresis. connect hyst to gnd to select 4 c hysteresis, to v dd to select 12 c hysteresis, or leave floating to select 8 c hystere- sis. the max6668 has a built-in hysteresis of 8 c. this allows the amount of hysteresis to be matched to the cooling and noise requirements of the system. figure 1 shows the temperature trip threshold hysteresis. applications information remote-diode selection the max6668/MAX6670 directly measure the die tem- perature of cpus and other ics that have on-board tem- perature-sensing diodes (see typical operating circuit ) or they can measure the temperature of a discrete diode-connected transistor. for best accuracy, the dis- crete transistor should be a small-signal device with its collector and base connected together. several satisfac- tory discrete sensing transistors are shown in table 1. the sensing transistor must be a small-signal type with a relatively high forward voltage. otherwise, the dxp input voltage range may be violated. the forward volt- age at the highest expected temperature must be greater than 0.25v at 10a, and at the lowest expected temperature, forward voltage must be less than 0.95v at 100a. do not use large power transistors. also, ensure that the base resistance is less than 100 ? . tight specifications for forward current gain (50 < b f < 150, for example) indicate that the manufacturer has good process controls and that the transistors have consis- tent v be characteristics. noise-filtering capacitor in noisy environments, high-frequency noise can be attenuated using an external 2200pf capacitor located at the dxp and dxn pins. larger capacitor values may be used for additional filtering, but do not exceed 3300pf; excessive capacitance increases error. figure 2 shows the recommended dxp/dxn pc traces. bypassing and layout the location of the remote-sensing junction in the sys- tem affects the max6668/MAX6670s operation. when using a discrete temperature-sensing transistor, place the sensing junction close to major heat-generating components, such as a high-speed cpu or a power device. to minimize noise and other errors, follow the guide- lines below: 1) place the max6668/MAX6670 as close as possible to the remote diode. in a noisy environment, such as a computer motherboard, this distance can be 10cm to 20cm (typ) or more as long as the worst noise sources (such as crts, clock generators, memory buses, and isa/pci buses) are avoided. in general, minimize the distance to the remote-sensing junction. 2) do not route the dxp/dxn traces next to the deflec- tion coils of a crt. also, do not route the traces across a fast memory bus, which can introduce +30 c error or more, even with good filtering. 3) route the dxp and dxn traces in parallel and in close proximity to each other, away from any high- voltage traces, such as +12vdc. avoid leakage cur- rents from pc board contamination, since a 20m ? leakage path from dxp to gnd causes about +1 c error. 4) connect guard traces to gnd on either side of the dxp/dxn traces (figure 2). with guard traces in place, routing near high-voltage traces is no longer an issue. 5) route through as few vias and crossunders as possi- ble to minimize copper/solder thermocouple effects. 6) use wide traces where possible. narrow traces are more inductive and tend to pick up radiated noise. 7) do not use copper as an emi shield. only ferrous materials such as steel work well. placing a copper ground plane between the dxp/dxn traces and other traces carrying high-frequency noise signals does not help reduce emi. the max6668/MAX6670s pgnd is the ground return for the fan driver. bypass v dd to gnd with a 1f capacitor located as close to v dd as possible. add additional bypass capacitors for long v dd and gnd lines. max6668/MAX6670 remote temperature switches with integrated fan controller/driver _______________________________________________________________________________________ 5 manufacturer model no. central semiconductor (usa) cmpt3904 on semiconductor (usa) 2n3904, 2n3906 rohm semiconductor (usa) sst3904 samsung (korea) kst3904-tf siemens (germany) smbt3904 zetex (england) fmmt3904ct-nd table 1. remote-sensor transistor manufacturers
max6668/MAX6670 chip information transistor count: 8113 process: bicmos remote temperature switches with integrated fan controller/driver 6 _______________________________________________________________________________________ gnd dxp dxn gnd 10mils 10mils 10mils minimum 10mils figure 2. recommended dxp/dxn pc traces trip temperature trip temperature ?hysteresis time max6668 MAX6670 fanout figure 1. temperature trip threshold hysteresis dxp gnd pgnd hyst v dd +4.5v to +12v MAX6670 forceon fanout warn ot v dd v dd dxn v dd +3v to +3.6v cpu typical operating circuit v dd gnd dxn 1 2 8 7 fanout gnd forceon dxp pgnd max top view 3 4 6 5 max6668 1 2 3 4 5 10 9 8 7 6 fanout hyst v dd gnd dxn dxp pgnd MAX6670 max ot forceon warn pin configurations ordering information part temp range pi n - pa c k a g e t h r esh - o l d ( c ) MAX6670 aub40 -40 c to +125 c 10 max 40 MAX6670aub45 -40 c to +125 c 10 max 45 MAX6670aub50 -40 c to +125 c 10 max 50 MAX6670aub55 -40 c to +125 c 10 max 55 MAX6670aub60 -40 c to +125 c 10 max 60 MAX6670aub65 -40 c to +125 c 10 max 65 MAX6670aub70 -40 c to +125 c 10 max 70 MAX6670aub75 -40 c to +125 c 10 max 75
max6668/MAX6670 remote temperature switches with integrated fan controller/driver _______________________________________________________________________________________ 7 t fan +30 c t fan +15 c t fan v dd temp sensor dxp dxn hyst c s 4 c, 8 c, 12 c hysteresis fanout pgnd warn ot MAX6670 gnd forceon functional diagrams t fan v dd temp sensor dxp dxn c s 8 c hysteresis fanout pgnd max6668 gnd forceon
max6668/MAX6670 remote temperature switches with integrated fan controller/driver maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2002 maxim integrated products printed usa is a registered trademark of maxim integrated products. 8lumaxd.eps package outline, 8l umax/usop 1 1 21-0036 j rev. document control no. approval proprietary information title: max 0.043 0.006 0.014 0.120 0.120 0.198 0.026 0.007 0.037 0.0207 bsc 0.0256 bsc a2 a1 c e b a l front view side view e h 0.60.1 0.60.1 ? 0.500.1 1 top view d 8 a2 0.030 bottom view 1 6 s b l h e d e c 0 0.010 0.116 0.116 0.188 0.016 0.005 8 4x s inches - a1 a min 0.002 0.950.75 0.5250 bsc 0.25 0.36 2.95 3.05 2.95 3.05 4.78 0.41 0.65 bsc 5.03 0.66 6 0 0.13 0.18 max min millimeters - 1.10 0.05 0.15 dim 10lumax.eps package outline, 10l umax/usop 1 1 21-0061 i rev. document control no. approval proprietary information title: top view front view 1 0.498 ref 0.0196 ref s 6 side view bottom view 0 0 6 0.037 ref 0.0078 max 0.006 0.043 0.118 0.120 0.199 0.0275 0.118 0.0106 0.120 0.0197 bsc inches 1 10 l1 0.0035 0.007 e c b 0.187 0.0157 0.114 h l e2 dim 0.116 0.114 0.116 0.002 d2 e1 a1 d1 min -a 0.940 ref 0.500 bsc 0.090 0.177 4.75 2.89 0.40 0.200 0.270 5.05 0.70 3.00 millimeters 0.05 2.89 2.95 2.95 - min 3.00 3.05 0.15 3.05 max 1.10 10 0.60.1 0.60.1 ? 0.500.1 h 4x s e d2 d1 b a2 a e2 e1 l l1 c gage plane a2 0.030 0.037 0.75 0.95 a1 package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .)
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