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general description the MAX6643/max6644/max6645 monitor temperature and automatically adjust fan speed to ensure optimum cooling while minimizing acoustic noise from the fan. each device measures two temperature locations. the MAX6643/max6644/max6645 generate a pwm waveform that drives an external power transistor, which in turn modulates the fan? power supply. the MAX6643/max6644/max6645 monitor temperature and adjust the duty cycle of the pwm output waveform to con- trol the fan? speed according to the cooling needs of the system. the MAX6643 monitors its own die temperature and an optional external transistor? temperature while the max6644 and max6645 each monitor the temperatures of one or two external diode-connected transistors. the MAX6643/max6644/max6645 are available in h and l versions. the h versions are trimmed for higher temperature trip thresholds than the l versions. the MAX6643 and max6644 have nine selectable trip tem- peratures (in 5 c increments). the max6645 is factory programmed and is not pin selectable. all versions include an overtemperature output ( ot ). ot can be used for warning or system shutdown. the MAX6643 also features a fullspd input that forces the pwm duty cycle to 100%. the MAX6643/max6644/ max6645 also feature a fanfail output that indicates a failed fan. see the selector guide for a complete list of each device? functions. the MAX6643 and max6644 are available in a small 16-pin qsop package and the max6645 is available in a 10-pin ?ax package. all versions operate from supply voltages from 3.0v to 5.5v and consume 500? (typ) supply current. applications networking equipment storage equipment servers desktop computers workstations features ? simple, automatic fan-speed control ? internal and external temperature sensing ? detect fan failure through locked-rotor output, tachometer output, or fan-supply current sensing ? multiple, 1.6% output duty-cycle steps for low audibility of fan-speed changes ? pin-selectable or factory-selectable low- temperature fan threshold ? pin-selectable or factory-selectable high- temperature fan threshold ? spin-up time ensures fan start ? fan-start delay minimizes power-supply load at power-up ? 32hz pwm output ? controlled duty-cycle rate of change ensures good acoustic performance ? 2 c temperature-measurement accuracy ? fullspd/ fullspd input sets pwm to 100% ? pin-selectable ot output threshold ? 16-pin qsop and 10-pin ?ax packages MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output ________________________________________________________________ maxim integrated products 1 ordering information 19-3305; rev 0; 5/04 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. pin configurations, typical operating circuit, and selector guide appear at end of data sheet. part temp range pin-package MAX6643 lbfaee -40 c to +125 c 16 qsop MAX6643lafaee* -40 c to +125 c 16 qsop MAX6643lbbaee* -40 c to +125 c 16 qsop MAX6643labaee* -40 c to +125 c 16 qsop MAX6643hafaee* -40 c to +125 c 16 qsop max6644 laaaee* -40 c to +125 c 16 qsop max6644hafaee* -40 c to +125 c 16 qsop max6645 aafaub* -40 c to +125 c 10 ?ax max6645bafaub* -40 c to +125 c 10 ?ax * future product?ontact factory for availability. ?ax is a registered trademark of maxim integrated products, inc.
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dd = +3.0v to +5.5v, t a = -40 c to +125 c, unless otherwise noted. typical values are at v dd = +3.3v, t a = +25?.) (note 1) 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 pwm_out, ot , and fanfail to gnd.....................-0.3v to +6v fan_in1 and fan_in2 to gnd...........................-0.3v to +13.2v dxp_ to gnd.........................................................-0.3v to +0.8v fullspd, fullspd , th_, tl_, tachset, and ot_ to gnd ......................................-0.3v to +(v dd + 0.3v) fanfail , ot current ..........................................-1ma to +50ma continuous power dissipation (t a = +70?) 16-pin qsop (derate 8.3mw/? above +70?).......... 667mw 10-pin ?ax (derate 5.6mw/? above +70?) ...........444mw operating temperature range .........................-40? to +125? junction temperature ......................................................+150? storage temperature range ............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units operating supply voltage range v dd +3.0 +5.5 v t a = +20? to +60? ? remote temperature error v dd = +3.3v, +20 c t rj +100 c t a = 0? to +125? ? c t a = +10? to +70? ?.5 local temperature error v cc = +3.3v t a = 0? to +125? ?.5 c temperature error from supply sensitivity ?.2 c/v power-on-reset (por) threshold v dd falling edge 1.5 2.0 2.5 v por threshold hysteresis 90 mv operating current i s during a conversion 0.5 1 ma average operating current duty cycle = 50%, no load 0.5 ma remote-diode sourcing current high level 80 100 120 ? conversion time 125 ms max664_ _a_ _ _ _ 2.5 spin-up time max664_ _b_ _ _ _ 8 s max664_ _a_ _ _ _ 2.5 startup delay max664_ _b_ _ _ _ 0.5 s minimum fan-fail tachometer frequency 16 hz pwm_out frequency f pwm_out 32 hz digital outputs ( ot , fanfail , pwm_out) output low voltage ( ot )v ol i sink = 1ma 0.4 v i sink = 6ma 0.5 output low voltage ( fanfail , pwm_out) v ol i sink = 1ma 0.4 v output high-leakage current i oh v oh = 3.3v 1 a note 1 : all parameters tested at t a = +25?. specifications over temperature are guaranteed by design.
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output _______________________________________________________________________________________ 3 operating supply current vs. supply voltage MAX6643 toc01 supply voltage (v) supply current ( a) 5.0 4.5 4.0 3.5 240 280 320 360 400 200 3.0 5.5 pwmout frequency vs. die temperature MAX6643 toc02 temperature ( c) pwmout frequency (hz) 100 85 60 35 10 -15 31.2 31.4 31.6 31.8 32.0 31.0 -40 trip-threshold error vs. trip temperature MAX6643 toc04 trip temperature ( c) trip-threshold error ( c) 80 60 40 -0.6 -0.2 0.2 0.6 1.0 -1.0 20 100 max664_l versions pwmout frequency vs. supply voltage MAX6643 toc03 supply voltage (v) pwmout frequency (hz) 5.0 4.5 4.0 3.5 31 32 33 34 35 30 3.0 5.5 typical operating characteristics (t a = +25?, unless otherwise noted.) electrical characteristics (continued) (v dd = +3.0v to +5.5v, t a = -40 c to +125 c, unless otherwise noted. typical values are at v dd = +3.3v, t a = +25?.) (note 1) parameter symbol conditions min typ max units digital inputs ( fullspd , fullspd, tachset) v dd = 5.5v 3.65 logic input high v ih v dd = 3.0v 2.2 v logic input low v il v dd = 3.0v 0.8 v input leakage current v in = gnd or v dd -1 +1 ? note 1 : all parameters tested at t a = +25?. specifications over temperature are guaranteed by design.
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output 4 _______________________________________________________________________________________ pin description pin MAX6643_a MAX6643_b max6644_ max6645_ name function 1, 15 1, 15 1, 15 th1, th2 high-temperature threshold inputs. connect to v dd , gnd, or leave unconnected to select the upper fan-control trip temperature (t high ), in 5? increments. see table 1. 2, 3 2, 3 2, 3 tl1, tl2 low-temperature threshold inputs. connect to v dd , gnd, or leave unconnected to select the lower fan-control trip temperature (t low ), in 5? increments. see table 2. 4441 fanfail fan-fail alarm output. fanfail is an active-low open-drain output. if the fan_in_ detects a fan failure, the fanfail output asserts low. 5552 tachset fan_in_ control input. tachset controls what type of fan- fail condition is being detected. connect tachset to v dd , gnd, or leave floating to set locked rotor, current sense, or tachometer configurations (see table 3). ? fullspd active-high logic input. when pulled high, the fan runs at 100% duty cycle. 6 fullspd active-low logic input. when pulled low, the fan runs at 100% duty cycle. 8 8 6, 8 3, 5 dxp, dxp1, dxp2 c om b i ned c ur r ent s our ce and a/d p osi ti ve inp ut for rem ote d i od e. c onnect to anod e of r em ote d i od e- connected tem p er atur e- sensi ng tr ansi stor . c onnect to g n d i f no r em ote d i od e i s used . p l ace a 2200p f cap aci tor b etw een d x p _ and g n d for noi se fi l ter i ng . 7 7 7 4 gnd ground 9996 ot active-low, open-drain overtemperature output. when ot threshold is exceeded, ot pulls low. 10 10 10 7 fan_in2 fan- s ense inp ut. fan _in 2 can b e confi g ur ed to m oni tor ei ther a fan s l og i c- l evel l ocked - r otor outp ut, tachom eter outp ut, or sense r esi stor w avefor m to d etect fan fai l ur e. the m ax 6643 s fan _in 2 i np ut can m oni tor onl y tachom eter si g nal s. the m ax 6644 and the m ax 6645 can m oni tor any one of the thr ee si g nal typ es as confi g ur ed usi ng the tac h s e t i np ut. 11 11 11 8 fan_in1 fan- s ense inp ut. fan _in 1 can b e confi g ur ed to m oni tor ei ther a fan s l og i c- l evel l ocked - r otor outp ut, tachom eter outp ut, or sense r esi stor w avefor m to d etect fan fai l ur e. the m ax 6643 s fan _in 1 i np ut can m oni tor onl y the tachom eter si g nal s. the m ax 6644 and the m ax 6645 can m oni tor any one of the thr ee si g nal typ es as confi g ur ed usi ng the tac h s e t i np ut.
detailed description the MAX6643/max6644/max6645 measure temperature and automatically adjust fan speed to ensure optimum cooling while minimizing acoustic noise from the fan. the MAX6643/max6644/max6645 generate a pwm waveform that drives an external power transistor, which in turn modulates the fan? power supply. the MAX6643/max6644/max6645 monitor temperature and adjust the duty cycle of the pwm output waveform to control the fan? speed according to the cooling needs of the system. the MAX6643 monitors its own die tem- perature and an optional external transistor? tempera- ture while the max6644 and max6645 each monitor the temperatures of one or two external diode-connect- ed transistors. temperature sensor the pn junction-based temperature sensor can mea- sure temperatures up to two pn junctions. the MAX6643 measures the temperature of an external diode-connected transistor, as well as its internal tem- perature. the max6644 and max6645 measure the temperature of two external diode-connected transis- tors. the temperature is measured at a rate of 1hz. if an external "diode" pin is shorted to ground or left unconnected, the temperature is read as 0?. since the larger of the two temperatures prevails, a faulty or unconnected diode is not used for calculating fan speed or determining overtemperature faults. pwm output the larger of the two measured temperatures is always used for fan control. the temperature is compared to three thresholds: the high-temperature threshold (t high ), the low-temperature threshold (t low ), and the overtem- perature threshold, ot . the ot comparison is done once per second, whereas the comparisons with fan-control thresholds t high and t low are done once every 4s. the duty-cycle variation of pwm_out from 0% to 100% is divided into 64 steps. if the temperature measured exceeds the threshold t high , the pwm_out duty cycle is incremented by one step, i.e., approximately 1.5% (100/64). similarly, if the temperature measured is below the threshold t low , the duty cycle is decremented by one step (1.5%). since the t high and t low compar- isons are done only once every 4s, the maximum rate of change of duty cycle is 0.4% per second. tables 1 and 2 shows the ? value assigned to the th_ and tl_ input combinations. MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output _______________________________________________________________________________________ 5 pin description (continued) pin MAX6643_a MAX6643_b max6644_ max6645_ name function 12 12 12 9 pwm_out pwm output for driving external power transistor. connect to the gate of an n-channel mosfet or to the base of an npn. pwmout requires a pullup resistor. the pullup resistor can be connected to a supply voltage as high as 5.5v, regardless of the supply voltage. 13, 14 13, 14 13, 14 ot1, ot2 overtemperature threshold inputs. connect to v dd , gnd, or leave unconnected to select the upper-limit ot fault output trip temperature, in 5? increments. see table 4. 16 16 16 10 v dd power-supply input. 3.3v nominal. bypass v dd to gnd with a 0.1? capacitor. th2 th1 t high (?) l suffix t high (?) h suffix 0 0 20 40 0 high-z 25 45 0 1 30 50 high-z 0 35 55 high-z high-z 40 60 high-z 1 45 65 1 0 50 70 1 high-z 55 75 1 1 60 80 table 1. setting t high (MAX6643 and max6644)
MAX6643/max6644/max6645 there are two options for the behavior of the pwm out- puts at power-up. option 1 (minimum duty cycle = 0): at power-up, the pwm duty cycle is zero. option 2 (minimum duty cycle = the start duty cycle): at power- up, there is a startup delay, after which the duty cycle goes to 100% for the spin-up period. after the startup delay and spin-up, the duty cycle drops to its minimum value. the minimum duty cycle is in the 0% to 50% range (see the selector guide ). to control fan speed based on temperature, t high is set to the temperature beyond which the fan should spin at 100%. t low is set to the temperature below which the duty cycle may be reduced to its minimum value. after power-up and spin-up (if applicable), the duty cycle reduces to its minimum value (either 0% or the start duty cycle). for option 1 (minimum duty cycle = 0), if the measured temperature remains below t high , the duty cycle remains at zero (see figure 1). if the temperature increases above t high , the duty cycle goes to 100% for the spin-up period, and then goes to the start duty cycle (for example, 40%). if the measured temperature remains above t high when temperature is next measured (4s later), the duty cycle begins to increase, incrementing by 1.5% every 4s until the fan is spinning fast enough to reduce the temperature below t high . for option 2 (minimum duty cycle = start duty cycle), if the measured temperature remains below t high , the duty cycle does not increase and the fan continues to run at a slow speed. if the temperature increases above t high , the duty cycle begins to increase, incre- menting by 1.5% every 4s until the fan is spinning fast enough to reduce the temperature below t high (see figure 2). in both cases, if only a small amount of extra cooling is necessary to reduce the temperature below automatic pwm fan-speed controllers with overtemperature output 6 _______________________________________________________________________________________ table 2. setting t low (MAX6643 and max6644) startup duty cycle temperature time time t high spin-up t low figure 1. temperature-controlled duty-cycle change with minimum duty cycle 30% startup max664_b has 30% pwm_out duty cycle during startup. duty cycle temperature time time t high t low spin-up figure 2. temperature-controlled duty-cycle change with minimum duty cycle 30% tl2 tl1 t low (?) l suffix t low (?) h suffix 0 0 15 35 0 high-z 20 40 0 1 25 45 high-z 030 50 high-z high-z 35 55 high-z 140 60 1 0 45 65 1 high-z 50 70 1 1 55 75
t high , the duty cycle may increase just a few percent above the minimum duty cycle. if the power dissipation or ambient temperature increases to a high-enough value, the duty cycle may eventually need to increase to 100%. if the ambient temperature or the power dissipation reduces to the point that the measured temperature is less than t low , the duty cycle begins slowly decre- menting until either the duty cycle reaches its minimum value or the temperature rises above t low . the small duty-cycle increments and slow rate of change of duty cycle (1.5% maximum per 4s) reduce the likelihood that the process of fan-speed control is acoustically objectionable. the "dead band" between t low and t high keeps the fan speed constant when the temperature is undergoing small changes, thus making the fan-control process even less audible. fan-fail sensing the MAX6643/max6644/max6645 feature a fanfail output. the fanfail output is an active-low, open- drain alarm. the MAX6643/max6644/max6645 detect fan failure either by measuring the fan? speed and rec- ognizing when it is too low, or by detecting a "locked- rotor" logic signal from the fan. fan-failure detection is enabled only when the duty cycle of the pwm drive sig- nal is equal to 100%. this happens during the spin-up period when the fan first turns on and whenever the temperature is above t high long enough that the duty cycle reaches 100%. many fans have open-drain tachometer outputs that produce periodic pulses (usually two pulses per revolu- tion) as the fan spins. these tachometer pulses are monitored by the fan_in_ inputs to detect fan failures. if a 2-wire fan with no tachometer output is used, the fan? speed can be monitored by using an external sense resistor at the source of the driving fet (see figure 3). in this manner, the variation in the current flowing through the fan develops a periodic voltage waveform across the sense resistor. this periodic waveform is then highpass filtered and ac-coupled to the fan_in input. any variations in the waveform that have an amplitude of more than ?50mv are converted to digital pulses. the frequency of these digital pulses is directly related to the speed of the rotation of the fan and can be used to detect fan failure. note that the value of the sense resistor must be matched to the characteristics of the fan? current waveform. choose a resistor that produces voltage variations of at least ?00mv to ensure that the fan? operation can be reliably detected. note that while most fans have current waveforms that can be used with this detection method, there may be some that do not produce reliable "tachometer" signals. if a 2-wire fan is to be used with fault detection, be sure that the fan is compatible with this technique. to detect fan failure, the analog sense-conditioned pulses or the tachometer pulses are deglitched and counted for 2s while the duty cycle is 100% (either dur- ing spin-up or when the duty cycle rises to 100% due to measured temperature). if more than 32 pulses are counted (corresponding to 480rpm for a fan that pro- duces two pulses per revolution), the fan is assumed to be functioning normally. if fewer than 32 pulses are received, the fanfail output is enabled and the pwm duty cycle to the fet transistor is either shut down in case of a single-fan (MAX6643) configuration or contin- ues normal operation in case of a dual-fan configuration (max6644/max6645). some fans have a locked-rotor logic output instead of a tachometer output. if a locked-rotor signal is to be used to detect fan failure, that signal is monitored for 2s while the duty cycle is 100%. if a locked-rotor signal remains active (low) for more than 2s, the fan is assumed to have failed. the MAX6643/max6644/max6645 have two channels for monitoring fan-failure signals, fan_in1 and fan_in2. for the MAX6643, the fan_in_ channels monitor a tachometer. the MAX6643? fault sensing can also be turned off by floating the tachset input. for the max6644 and max6645, the fan_in1 and fan_in2 channels can be configured to monitor either a logic-level tachometer signal, the voltage waveform on a current-sense resistor, or a locked-rotor logic sig- nal. the tachset input selects which type of signal is to be monitored (see table 3). to disable fan-fault sensing, tachset should be unconnected and fan_in1 and fan_in2 should be connected to v dd . ot output the MAX6643/max6644/max6645 include an over- temperature output that can be used as an alarm or a system-shutdown signal. whenever the measured tem- perature exceeds the value selected using the ot pro- gramming inputs ot1 and ot2 (see table 4), ot is asserted. ot deasserts only after the temperature drops below the threshold. fullspd input the MAX6643_a_ features a fullspd input. pulling fullspd low forces pwm_out to 100% duty cycle. the fullspd input allows a microcontroller to force the fan to full speed when necessary. it also allows a fanfail output to force other fans to 100% in multifan MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output _______________________________________________________________________________________ 7
MAX6643/max6644/max6645 systems, or for an overtemperature condition (by con- necting ot to fullspd ). fullspd input the MAX6643_b_ features a fullspd input. pulling fullspd high forces pwm_out to 100% duty cycle. the fullspd input allows a microcontroller to force the fan to full speed when necessary. by connecting fanfail to an inverter, the MAX6643_b_ can force other fans to 100% in multifan systems, or for an over- temperature condition (by connecting ot inverter to fullspd). applications information figures 3? show various configurations. remote-diode considerations when using an external thermal diode, temperature accuracy depends upon having a good-quality, diode- connected, small-signal transistor. accuracy has been experimentally verified for a variety of discrete small- signal transistors, some of which are listed in table 6. the MAX6643/max6644/max6645 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 adc 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. effect of ideality factor the accuracy of the remote temperature measurements depends on the ideality factor (n) of the remote "diode" (actually a transistor). the MAX6643/max6644/ max6645 are optimized for n = 1.01, which is typical of many discrete 2n3904 and 2n3906 transistors. it is also near the ideality factors of many widely available cpus, gpus, and fpgas. however, any time a sense transis- tor with a different ideality factor is used, the output data is different. fortunately, the difference is predictable. automatic pwm fan-speed controllers with overtemperature output 8 _______________________________________________________________________________________ manufacturer model no. central semiconductor (usa) cmpt3906 rohm semiconductor (usa) sst3906 samsung (korea) kst3906-tf siemens (germany) smbt3906 table 5. remote-sensor transistor manufacturers ot2 ot1 t overt (?) l suffix t overt (?) h suffix 0 0 60 80 0 high-z 65 85 0 1 70 90 high-z 075 95 high-z high-z 80 100 high-z 1 85 105 1 0 90 110 1 high-z 95 115 1 1 100 120 table 4. setting the overtemperature thresholds (t overt ) (MAX6643 and max6644) table 3. configuring the fan_in_ inputs with tachset vdd gnd unconnected tachset fan_in1 fan_in2 fan_in1 fan_in2 fan_in1 fan_in2 MAX6643_a_ tachometer tachometer do not connect to gnd do not connect to gnd disables fan- failure detection disables fan- failure detection max6644_a_ tachometer tachometer current sense current sense locked rotor locked rotor max6645_a_ tachometer tachometer current sense current sense locked rotor locked rotor MAX6643_b_ tachometer tachometer do not connect to gnd do not connect to gnd disables fan- failure detection disables fan- failure detection max6644_b_ tachometer tachometer current sense current sense locked rotor locked rotor max6645_b_ tachometer tachometer current sense current sense locked rotor locked rotor
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output _______________________________________________________________________________________ 9 max6644 1 2 3 4 th1 tl2 tl1 fanfail tachset dxp2 gnd dxp1 v dd th2 ot1 ot2 pwm_out fan_in1 fan_in2 ot 5 6 7 8 16 15 4.7k ? 4.7k ? +v fan (5v or 12v) v dd (+3.0v to +5.5v) +v fan (5v or 12v) 2.0 ? 2.0 ? 4.7k ? to fanfail alarm 0.1 f 0.1 f 14 13 current-sense mode current-sense mode to overtemperature alarm 12 11 10 9 n n max6645 1 fanfail tachset dxp2 gnd dxp1 v dd pwm_out fan_in1 fan_in2 ot 2 3 4 5 4.7k ? 4.7k ? +v fan (5v or 12v) v dd (+3.0v to +5.5v) +v fan (5v or 12v) 4.7k ? to fanfail alarm 10 tachometer mode tachometer mode to overtemperature alarm 9 8 7 6 n figure 3. max6644 using two external transistors to measure remote temperatures and control two 2-wire fans. the fan? power- supply current is monitored to detect failure of either fan. connect pin 10 to pin 11 if only one fan is used. figure 4. max6645 using two external transistors to measure remote temperatures and control two 2-wire cooling fans. the fan? power-supply current is monitored to detect failure of either fan. conect fan_in1 to fan_in2 if only one fan is used.
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output 10 ______________________________________________________________________________________ to fanfail alarm max6645 10 n 9 8 tachometer mode tachometer mode to overtemperature alarm 7 6 fanfail tachset dxp2 gnd dxp1 v dd v dd (+3.0v to +5.5v) +v fan (5v or 12v) 1 2 3 4 5 pwm_out fan_in1 fan_in2 ot 4.7k ? 4.7k ? 4.7k ? figure 5. using the max6645 to monitor two fans
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output ______________________________________________________________________________________ 11 MAX6643_a_ th1 16 15 14 13 12 11 (tachometer mode) (tachometer mode) to overtemperature alarm 10 9 tl2 tl1 fanfail to fanfail alarm to fanfail alarm tachset fullspd gnd dxp v dd v dd (+3.0v to +5.5v) +v fan (5v or 12v) 1 2 3 4 5 6 7 8 th2 ot1 ot2 pwm_out fan_in1 fan_in2 ot 4.7k ? 4.7k ? 4.7k ? n n MAX6643_a_ th1 16 15 14 13 12 11 (tachometer mode) (tachometer mode) to overtemperature alarm 10 9 tl2 tl1 fanfail tachset fullspd gnd dxp v dd v dd (+3.0v to +5.5v) +v fan (5v or 12v) 1 2 3 4 5 6 7 8 th2 ot1 ot2 pwm_out fan_in1 fan_in2 ot 4.7k ? 4.7k ? 4.7k ? figure 6. using two MAX6643s, each controlling a separate fan
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output 12 ______________________________________________________________________________________ assume a remote-diode sensor designed for a nominal ideality factor n is used to measure the temperature of a diode with a different ideality factor, n 1 . the measured temperature t m can be corrected using: where temperature is measured in kelvin. as mentioned above, the nominal ideality factor of the MAX6643/max6644/max6645 is 1.01. as an example, assume the MAX6643/max6644/max6645 are config- ured with a cpu that has an ideality factor of 1.008. if the diode has no series resistance, the measured data is related to the real temperature as follows: for a real temperature of +60? (333.15k), the mea- sured temperature is 59.33? (332.49k), which is an error of -0.66?. effect of series resistance series resistance in a sense diode contributes addition- al errors. for nominal diode currents of 10? and 100?, change in the measured voltage is: since 1? corresponds to 198.6?, series resistance contributes a temperature offset of: assume that the diode being measured has a series resistance of 3 ? . the series resistance contributes an offset of: the effects of the ideality factor and series resistance are additive. if the diode has an ideality factor of 1.008 and series resistance of 3 ? , the total offset can be cal- culated by adding error due to series resistance with error due to ideality factor: 1.36? - 0.66? = 0.7? for a diode temperature of 60.7?. in this example, the effect of the series resistance and the ideality factor partially cancel each other. for best accuracy, the discrete transistor should be a small-signal device with its collector connected to base and emitter connected to gnd. table 5 lists examples of discrete transistors that are appropriate for use with the MAX6643/max6644/max6645. the transistor must have a relatively high forward volt- age; otherwise, the adc input voltage range can be vio- lated. the forward voltage at the highest expected temperature must be greater than 0.25v at 10?, and at the lowest expected temperature, the forward voltage must be less than 0.95v at 100?. large power transis- tors must not be used. also, ensure that the base resis- tance is less than 100 ? . tight specifications for forward current gain (50 < ?<150, for example) indicate that the manufacturer has good process controls and that the devices have consistent v be 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 pc board carefully with proper external noise filtering for high-accuracy remote measurements in electrically noisy environments. filter high-frequency electromagnetic interference (emi) at the dxp pins with an external 2200pf capaci- tor connected between dxp, dxp1, or dxp2 and ground. this capacitor can be increased to about 3300pf (max), including cable capacitance. a capaci- tance higher than 3300pf introduces errors due to the rise time of the switched-current source. twisted pairs 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 electron- ics laboratory. for longer distances, the best solution is a shielded twisted pair like that used for audio micro- phones. for example, belden 8451 works well for dis- tances up to 100ft in a noisy environment. connect the twisted pair to dxp and gnd and the shield to ground, and leave the shield? remote end unterminated. excess capacitance at dxp limits practical remote-sensor dis- tances (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 3 c c ? ? = . . 0 453 1 36 90 198 6 0 453 = v v c c ? ? . . ? v m =? () =? raa ar ss 100 10 90 tt n n t 1.01 1.008 t actual m nominal 1 mm = ? ? ? ? ? ? = ? ? ? ? ? ? = () . 1 00198 tt n n m actual 1 nominal = ? ? ? ? ? ?
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output ______________________________________________________________________________________ 13 in value. cable resistance also affects remote-sensor accuracy. a 1 ? series resistance introduces about +1/2? error. pc board layout checklist 1) place the MAX6643/max6644/max6645 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 lines next to the deflection coils of a crt. also, do not route the traces across a fast memory bus, which can easily introduce +30? error, even with good filtering. otherwise, most noise sources are fairly benign. 3) route the dxp and gnd traces parallel and close to each other, away from any high-voltage traces such as +12vdc. avoid leakage currents from pc board contamination. a 20m ? leakage path from dxp to ground causes approximately +1? error. 4) route as few vias and crossunders as possible to minimize copper/solder thermocouple effects. 5) when introducing a thermocouple, make sure that both the dxp and the gnd paths have matching thermocouples. in general, pc board-induced ther- mocouples are not a serious problem. a copper sol- der thermocouple exhibits 3?/?, and it takes approximately 200? of voltage error at dxp/gn to cause a +1? measurement error, so most parasitic thermocouple errors are swamped out. 6) use wide traces. narrow traces are more inductive and tend to pick up radiated noise. the 10-mil widths and spacings are recommended, but are not absolutely necessary (as they offer only a minor improvement in leakage and noise), but use them where practical. 7) placing an electrically clean copper ground plane between the dxp traces and traces carrying high- frequency noise signals helps reduce emi. chip information transistor count: 12,518 process: bicmos pin configurations 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 th1 v dd th2 ot1 ot2 pwm_out fan_in1 fan_in2 ot top view MAX6643_a _ MAX6643_b_ qsop tl2 tl1 fullspd (fullspd) fanfail tachset gnd dxp 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 th1 v dd th2 ot1 ot2 pwm_out fan_in1 fan_in2 ot max6644_ _ qsop tl2 tl1 dxp2 fanfail tachset gnd dxp1 1 2 3 4 5 10 9 8 7 6 v dd pwm_out fan_in1 fan_in2 gnd dxp2 tachset fanfail max6645_ _ max ot dxp1
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output 14 ______________________________________________________________________________________ part package-pins startup delay (s) spin-up time (s) start duty cycle (%) minimum duty cycle (%) channels tl ( c) th ( c) ot ( c) fullspd polarity fan_in1 fan_in2 MAX6643 lbfaee qsop-16 0.5 8 40 40 remote, local 15?5 20?0 60?00 fullspd tach/off tach/off MAX6643 lafaee* qsop-16 2.5 2.5 40 40 remote, local 15?5 20?0 60?00 fullspd tach/off tach/off MAX6643 lbbaee* qsop-16 0.5 8 30 30 remote, local 15?5 20?0 60?00 fullspd tach/off tach/off MAX6643 labaee* qsop-16 2.5 2.5 30 30 remote, local 15?5 20?0 60?00 fullspd tach/off tach/off MAX6643 hafaee* qsop-16 2.5 2.5 40 40 remote, local 35?5 40?0 80?20 fullspd tach/off tach/off max6644 laaaee qsop-16 0.5 8 30 0 remote, remote 15?5 20?0 60?00 locked r otor /tach/ cur r ent sense locked r otor /tach/ cur r ent sense max6644 hafaee* qsop-16 2.5 2.5 40 40 remote, remote 35?5 40?0 80?20 locked r otor /tach/ cur r ent sense locked r otor /tach/ cur r ent sense max6645 aafaub** ?ax-10 0.5 8 40 40 remote, remote 45 50 75 locked r otor /tach/ cur r ent sense locked r otor /tach/ cur r ent sense max6645 bafaub** * ?ax-10 2.5 2.5 40 40 remote, remote 55 65 120 locked r otor /tach/ cur r ent sense locked r otor /tach/ cur r ent sense selector guide * future product?ontact factory for availability. ** the max6645xxxxxx may be ordered with any combination of tl, th, and ot trip threshold (in 5c increments) by contacting the fa ctory.
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output ______________________________________________________________________________________ 15 MAX6643 max6644 max6645 dxp1/(dxp) dxp2 temperature sensor temperature logic pwm generator fan-fail detection duty cycle analog sense tachometer locked rotor in analog sense tachometer locked rotor in ot th tl threshold selection fullspd/(fullspd) pwm_out fan_in1 fan_in2 fanfail tachset ot1 ot2 th1 th2 tl1 tl2 block diagram to fanfail alarm MAX6643_a_ th1 16 15 14 13 12 11 (tachometer mode) (tachometer mode) to overtemperature alarm 10 9 tl2 tl1 fanfail tachset fullspd gnd dxp v dd v dd (+3.0v to +5.5v) +v fan (5v or 12v) 1 2 3 4 5 6 7 8 th2 ot1 ot2 pwm_out fan_in1 fan_in2 ot 4.7k ? 4.7k ? 4.7k ? n typical operating circuit
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output 16 ______________________________________________________________________________________ package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .) qsop.eps e 1 1 21-0055 package outline, qsop .150", .025" lead pitch
MAX6643/max6644/max6645 automatic pwm fan-speed controllers with overtemperature output 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 ____________________ 17 2004 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .) 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 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

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