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general description the max6615/max6616 monitor two temperature chan- nels, either the internal die temperature and the temper- ature of an external thermistor, or the temperatures of two external thermistors. the temperature data controls a pwm output signal to adjust the speed of a cooling fan, thereby minimizing noise when the system is run- ning cool, but providing maximum cooling when power dissipation increases. the fans?tachometer output sig- nals are monitored by the max6615/max6616 to detect fan failure. if a fan failure is detected, the fan_fail output is asserted. the 2-wire serial interface accepts standard system management bus (smbus tm ) write byte, read byte, send byte, and receive byte commands to read the temperature data and program the alarm thresholds. the programmable alarm output can be used to gener- ate interrupts, throttle signals, or overtemperature shut- down signals. the max6616 features six gpios to provide additional flexibility. all of the gpios power-up as inputs, with the exception of gpio0, which powers up as either an input or an output as determined by connecting the preset pin to ground or v cc . the max6616 is available in a 24-pin qsop package, while the max6615 is available in a 16-pin qsop pack- age. both devices operate from a single-supply voltage range of 3.0v to 5.5v, have operating temperature ranges of -40? to +125?, and consume just 500? of supply current. applications desktop computers servers power supplies networking equipment workstations features two thermistor inputs two open-drain pwm outputs for fan-speed control local temperature sensor six gpios (max6616) programmable fan-control characteristics controlled pwm rate-of-change ensures unobtrusive fan-speed adjustments fail-safe system protection ot output for throttling or shutdown nine different pin-programmable smbus addresses 16-pin and 24-pin qsop packages max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs ________________________________________________________________ maxim integrated products 1 19-3713; rev 2; 10/08 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. ordering information part temp range pin-package max6615 aee -40? to +125? 16 qsop max6616 aeg -40? to +125? 24 qsop smbus is a trademark of intel corp. typical application circuits and pin configurations appear at end of data sheet. thermistors and local temp sensor pwm generator and tach counter smbus interface and registers logic add0 add1 *max6616 only fan_fail max6615 max6616 gnd v cc sda scl ref th1 th2 pwm1 pwm2 tach1 tach2 ot gpio0* gpio5* preset* functional diagram
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs 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 are referenced to gnd supply voltage (v cc ) ...............................................-0.3v to +6v pwm_, tach_, ot , fan_fail ............................-0.3v to +13.5v add0, add1, sda, scl ..........................................-0.3v to +6v all other pins..............................................-0.3v to (v cc + 0.3v) sda, ot , fan_fail , pwm_, gpio_ current....................?0ma th_ current ........................................................................?ma ref current ......................................................................?0ma continuous power dissipation (t a = +70?) 16-pin qsop (derated at 8.3mw/? above +70?)............................................................666.7mw 24-pin qsop (derated at 9.5mw/? above +70?)...........................................................761.9 mw esd protection (all pins, human body model) ....................?kv operating temperature range .........................-40? to +125? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? electrical characteristics (v cc = +3.0v to +5.5v, t a = 0? to +125?, unless otherwise noted. typical values are at v cc = +3.3v, t a = +25?.) parameter symbol conditions min typ max units operating supply voltage v cc 3.0 5.5 v standby current interface inactive, adc in idle state 10 ? operating current i s interface inactive, adc active 0.5 1 ma external temperature error v cc = +3.3v, 0.15v v th_ +0.71v (excludes thermistor errors, thermistor nonlinearity) (note1) ? ? v cc = +3.3v, 0? t a +85?, ?.5 internal temperature error v cc = +3.3v, 0? t a +125? 4 ? temperature resolution 0.125 ? conversion time 250 ms conversion rate timing error -20 +20 % pwm frequency error -20 +20 % input/output output low voltage v ol v cc = +3v, i out = 6ma 0.4 v output high leakage current i oh 1a logic low input voltage v il 0.8 v logic high input voltage v ih 2.1 v input leakage current 1a input capacitance c in 5pf smbus timing (figures 2, 3) (note 2) serial clock frequency f sclk 10 400 khz clock low period t low 10% to 10% 4 s clock high period t high 90% to 90% 4.7 ? bus free time between stop and start conditions t buf 4.7 ? smbus start condition setup time t su:sta 90% of scl to 90% of sda 4.7 ?
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs _______________________________________________________________________________________ 3 note 1: 1? of error corresponds to an adc error of 7.76mv when v ref = 1v. note 2: guaranteed by design and characterization. note 3: production tested. electrical characteristics (continued) (v cc = +3.0v to +5.5v, t a = 0? to +125?, unless otherwise noted. typical values are at v cc = +3.3v, t a = +25?.) parameter symbol conditions min typ max units start condition hold time t hd:sto 10% of sda to 10% of scl 4 s stop condition setup time t su:sto 90% of scl to 10% of sda 4 s data setup time t su:dat 10% of sda to 10% of scl 250 ns data hold time t hd:dat 10% of scl to 10% of sda 300 ns smbus fall time t f 300 ns smbus rise time t r 1000 ns smbus timeout (note 3) 29 37 55 ms typical operating characteristics (v cc = +3.3v, t a = +25?, unless otherwise noted.) supply current vs. supply voltage max6615/6 toc01 supply voltage (v) supply current ( a) 5.0 4.5 4.0 3.5 10 100 1000 1 3.0 5.5 local remote shutdown 0 40 20 80 60 100 120 thermistor temperature data vs. thermistor temperature max6615/6 toc02 thermistor temperature ( c) thermistor temperature data ( c) 04060 20 80 100 120 local temperature error vs. die temperature max6615/6 toc03 die temperature ( c) temperature error ( c) 75 50 25 -1 0 1 2 -2 0100
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs 4 _______________________________________________________________________________________ typical operating characteristics (continued) (v cc = +3.3v, t a = +25?, unless otherwise noted.) gpio sink current vs. supply voltage max6615/6 toc04 v cc (v) i gpio_ (ma) 5.0 4.5 4.0 3.5 20 25 30 35 40 45 50 15 3.0 5.5 v gpio_ = 0.4v gpio output voltage vs. gpio sink current max6615/6 toc05 i gpio_ (ma) v gpio_ (v) 70 60 40 50 20 30 10 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 080 v cc = 3v v cc = 5v -5 -2 -3 -4 -1 0 1 2 3 4 5 050 25 75 100 125 pwm frequency vs. die temperature max6615/6 toc06 die temperature ( c) frequency shift (hz) normalized at t a = +25 c -0.04 0 -0.02 0.04 0.02 0.08 0.06 0.10 3.0 4.0 3.5 4.5 5.0 5.5 pwm frequency vs. supply voltage max6615/6 toc07 v cc (v) frequency shift (hz) normalized at v cc = 5.0v
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs _______________________________________________________________________________________ 5 pin max6616 max6615 name function 1, 2, 5, 20, 23, 24 gpio0 gpio5 active-low, open-drain gpios. can be pulled up to 5.5v regardless of v cc . 3 1 pwm1 fan driver output 1. the pullup resistor can be connected to a supply voltage as high as 12v, regardless of the supply voltage. see the pwm output section for configuration. 4 2 tach1 fan tachometer input. accepts logic-level signal from fan? tachometer output. can be connected to a supply voltage as high as 12v, regardless of the supply voltage. 6 3 add0 smbus slave address selection 7 4 add1 smbus slave address selection 8 5, 10 gnd ground. must be connected together for max6615. 9 6 th1 external thermistor input 1. connect a thermistor in series with a fixed resistor between ref and ground. 10, 15 n.c. no connection 11 7 ref reference voltage output. provides 1v during measurements. high impedance when not measuring. 12 8 th2 external thermistor input 2. connect a thermistor in series with a fixed resistor between ref and ground. 13 9 fan_fail fan-failure output. asserts low when either fan fails. can be pulled up as high as 5.5v regardless of v cc . high impedance when v cc = 0v. 14 preset connect to gnd or v cc to set por state of the gpio0. 16 11 ot overtemperature output. active low, open drain. typically used for system shutdown or clock throttling. can be pulled up as high as 5.5v regardless of v cc . high impedance when v cc = 0v. 17 12 v cc power supply. 3.3v nominal. bypass with a 0.1? capacitor to gnd. 18 13 sda smbus serial-data input/output. pull up with a 10k ? resistor. can be pulled up as high as 5.5v regardless of v cc . high impedance when v cc = 0v. 19 14 scl smbus serial-clock input. pull up with a 10k ? resistor. can be pulled up as high as 5.5v regardless of v cc . high impedance when v cc = 0v. 21 15 tach2 fan tachometer input. accepts logic-level signal from fan? tachometer output. can be connected to a supply voltage as high as 12v, regardless of the supply voltage. 22 16 pwm2 fan driver output 2. the pullup resistor can be connected to a supply voltage as high as 12v, regardless of the supply voltage. see the pwm output section for configuration. pin description
max6615/max6616 detailed description the max6615/max6616 accurately monitor two tem- perature channels, either the internal die temperature and the temperature of an external thermistor, or the temperatures of two external thermistors. they report temperature values in digital form using a 2-wire smbus/i 2 c*-compatible serial interface. the max6615/ max6616 operate from a supply voltage range of 3.0v to 5.5v and consume 500? (typ) of supply current. the temperature data controls the duty cycles of two pwm output signals that are used to adjust the speed of a cooling fan. they also feature an overtemperature alarm output to generate interrupts, throttle signals, or shutdown signals. the max6616 also includes six gpio input/outputs to provide additional flexibility. the gpio0 power-up state is set by connecting the gpio preset input to ground or v cc . smbus digital interface from a software perspective, the max6615/max6616 appear as a set of byte-wide registers. their devices use a standard smbus 2-wire/i 2 c-compatible serial interface to access the internal registers. the max6615/max6616 have nine different slave addresses available; therefore, a maximum of nine max6615/max6616 devices can share the same bus. the max6615/max6616 employ four standard smbus protocols: write byte, read byte, send byte, and receive byte (figures 1, 2, and 3). the shorter receive byte proto- col allows quicker transfers, provided that the correct data register was previously selected by a read byte instruction. use caution with the shorter protocols in mul- timaster systems, since a second master could overwrite the command byte without informing the first master. temperature data can be read from registers 00h and 01h. the temperature data format for these registers is 8 bits, with the lsb representing 1? (table 1) and the msb representing 128?. the msb is transmitted first. all values below 0? clip to 00h. table 3 details the register address and function, whether they can be read or written to, and the power-on reset dual-channel temperature monitors and fan-speed controllers with thermistor inputs 6 _______________________________________________________________________________________ write byte format send byte format receive byte format slave address: equiva- lent to chip-select line of a 3-wire interface command byte: selects which register you are writing to data byte: data goes into the reg- ister set by the command byte (to set thresholds, configuration masks, and sampling rate) slave address: equivalent to chip- select line command byte: selects which register you are reading from slave address: repeat- ed due to change in data- flow direction data byte: reads from the register set by the command byte command byte: sends com- mand with no data, usually used for one-shot command data byte: reads data from the register commanded by the last read byte or write byte transmission; also used for smbus alert response return address s = start condition shaded = slave transmission p = stop condition /// = not acknowledged figure 1. smbus protocols s address rd ack data /// p 7 bits 8 bits wr s ack command ack p 8 bits address 7 bits p 1 ack data 8 bits ack command 8 bits ack wr address 7 bits s s address wr ack command ack s address 7 bits 8 bits 7 bits rd ack data 8 bits /// p * purchase of i 2 c components from maxim integrated products, inc., or one of its sublicensed associated companies, conveys a license under the philips i 2 c patent rights to use these com- ponents in an i 2 c system, provided that the system conforms to the i 2 c standard specification as defined by philips.
(por) state. see tables 3? for all other register functions and the register descriptions section. temperature measurements the averaging adc integrates over a 120ms period (each channel, typically), with excellent noise rejection. for internal temperature measurements, the adc and associated circuitry measure the forward voltage of the internal sensing diode at low- and high-current levels and compute the temperature based on this voltage. for thermistor measurements, the reference voltage and the thermistor voltage are measured and offset is applied to yield a value that correlates well to thermistor temperature within a wide temperature range. both channels are automatically converted once the conver- sion process has started. if one of the two channels is not used, the circuit still performs both measurements, and the data from the unused channel may be ignored. if either of the measured temperature values is below 0? the value in the corresponding temperature register is clipped to zero when a negative offset is pro- grammed into the thermistor offset register (17h). local (internal) temperature data is expressed directly in degrees celsius. two registers contain the tempera- ture data for the local channel. the high-byte register has an msb of 128? and an lsb of 1?. the low- byte register contains 3 bits, with an msb of 0.5? and an lsb of 0.125?. the data format is shown in table 1. thermistors allow measurements of external tempera- tures. connect a thermistor in series with a resistor, r ext . the thermistor should be connected between the th_ input and ground, and r ext should be connected between the reference output, ref, and the th_ input, as shown in the typical application circuit . the voltage across r ext is measured by the adc, resulting in a value that is directly related to tempera- max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs _______________________________________________________________________________________ 7 smbclk a = start condition b = msb of address clocked into slave c = lsb of address clocked into slave d = r/w bit clocked into slave ab cd e fg hij smbdata t su:sta t hd:sta t low t high t su:dat t su:sto t buf lm k e = slave pulls smbdata line low f = acknowledge bit clocked into master g = msb of data clocked into slave h = lsb of data clocked into slave i = master pulls data line low j = acknowledge clocked into slave k = acknowledge clock pulse l = stop condition m = new start condition figure 2. smbus write timing diagram smbclk ab cd e fg h i j k smbdata t su:sta t hd:sta t low t high t su:dat t hd:dat t su:sto t buf a = start condition b = msb of address clocked into slave c = lsb of address clocked into slave d = r/w bit clocked into slave e = slave pulls smbdata line low l m f = acknowledge bit clocked into master g = msb of data clocked into master h = lsb of data clocked into master i = master pulls data line low j = acknowledge clocked into slave k = acknowledge clock pulse l = stop condition m = new start condition figure 3. smbus read timing diagram
max6615/max6616 ture. the thermistor data in the temperature register(s) gives the voltage across r ext as a fraction of the refer- ence voltage. the lsb of the high byte has a nominal weight of 7.68mv. o o t t output the ot output asserts when a thermal fault occurs, and can therefore be used as a warning flag to initiate sys- tem shutdown, or to throttle clock frequency. when temperature exceeds the ot temperature threshold and ot is not masked, the ot status register indicates a fault and ot output becomes asserted. if ot for the respective channel is masked off, the ot status register continues to be set, but the ot output does not become asserted. the fault flag and the output can be cleared by reading the ot status register. the ot output can also be cleared by masking the affected channel. if the ot sta- tus bit is cleared, ot reasserts on the next conversion if the temperature still exceeds the ot temperature threshold. pwm output the pwm_ signals are normally used in one of three ways to control the fan? speed: 1) pwm_ drives the gate of a mosfet or the base of a bipolar transistor in series with the fan? power sup- ply. the typical application circuit shows the pwm_ driving an n-channel mosfet. in this case, the pwm invert bit (d4 in register 02h) is set to 1. figure 4 shows pwm_ driving a p-channel mosfet and the pwm invert bit must be set to zero. 2) pwm_ is converted (using an external circuit) into a dc voltage that is proportional to duty cycle. this duty-cycle-controlled voltage becomes the power supply for the fan. this approach is less efficient than (1), but can result in quieter fan operation. figure 5 shows an example of a circuit that converts the pwm signal to a dc voltage. because this circuit produces a full-scale output voltage when pwm = 0v, bit d4 in register 02h should be set to zero. 3) pwm_ directly drives the logic-level pwm speed- control input on a fan that has this type of input. this approach requires fewer external components and combines the efficiency of (1) with the low noise of (2). an example of pwm_ driving a fan with a speed- control input is shown in figure 6. bit d4 in register 02h should be set to 1 when this configuration is used. whenever the fan has to start turning from a motionless state, pwm_ is forced high for 2s. after this spin-up period, the pwm_ duty cycle settles to the predeter- mined value. whenever spin-up is disabled (bit 2 in the configuration byte = 1) and the fan is off, the duty cycle changes immediately from zero to the nominal value, ignoring the duty-cycle rate-of-change setting. the frequency-select register controls the frequency of the pwm signal. when the pwm signal modulates the power supply of the fan, a low pwm frequency (usually 33hz) should be used to ensure the circuitry of the dual-channel temperature monitors and fan-speed controllers with thermistor inputs 8 _______________________________________________________________________________________ table 1. temperature data format (high byte and low byte) high byte low byte temperature (?) binary value hex value binary value hex value 140.0 1000 1100 8ch 0000 0000 00h 127.0 0111 1111 7fh 0000 0000 00h 25.375 0001 1001 19h 0110 0000 60h 25.0 0001 1001 19h 0000 0000 00h 0.5 0000 0000 00h 1000 0000 80h 0.0 0000 0000 00h 0000 0000 00h <0 0000 0000 00h 0000 0000 00h v cc pwm 10k ? 5v p figure 4. driving a p-channel mosfet for top-side pwm fan drive
brushless dc motor has enough time to operate. when driving a fan with a pwm-to-dc circuit as shown in figure 5, the highest available frequency (35khz) should be used to minimize the size of the filter capacitors. when using a fan with a pwm control input, the frequen- cy normally should be high as well, although some fans have pwm inputs that accept low-frequency drive. the duty cycle of the pwm can be controlled in two ways: 1) manual pwm control: setting the duty cycle of the fan directly through the fan target duty-cycle registers (0bh and 0ch). 2) automatic pwm control: setting the duty cycle based on temperature. manual pwm duty-cycle control clearing the bits that select the temperature channels for fan control (d5 and d4 for pwm1 and d3 and d2 for pwm2) in the fan-configuration register (11h) enables manual fan control. in this mode, the duty cycle written to the fan target duty-cycle register directly controls the corresponding fan. the value is clipped to a maximum of 240. any value entered above that is changed to 240 automatically. in this control mode, the value in the maxi- mum duty-cycle register is ignored and does not affect the duty cycle used to control the fan. automatic pwm duty-cycle control in the automatic control mode, the duty cycle is con- trolled by the local or remote temperature according to the settings in the control registers. below the fan-start temperature, the duty cycle is either 0% or is equal to the fan-start duty cycle, depending on the value of bit d3 in the configuration byte register. above the fan- start temperature, the duty cycle increases by one duty-cycle step each time the temperature increases by one temperature step. the target duty cycle is calculat- ed based on the following formula; for temperature > fanstarttemperature: where: dc = dutycycle fsdc = fanstartdutycycle t = temperature fst = fanstarttemperature dcss = dutycyclestepsize ts = tempstep duty cycle is recalculated after each temperature con- version if temperature is increasing. if the temperature begins to decrease, the duty cycle is not recalculated until the temperature drops by 5? from the last peak temperature. the duty cycle remains the same until the temperature drops 5? from the last peak temperature or the temperature rises above the last peak temperature. for example, if the temperature goes up to +85? and starts decreasing, duty cycle is not recalculated until the temperature reaches +80? or the temperature rises above +85?. if the temperature decreases further, the duty cycle is not updated until it reaches +75?. for temperature < fanstarttemperature and d2 of configuration register = 0: dutycycle = 0 for temperature < fanstarttemperature and d2 of configuration register = 1: dutycycle = fanstartdutycycle once the temperature crosses the fan-start temperature threshold, the temperature has to drop below the fan- start temperature threshold minus the hysteresis before dc fsdc t fst dcss ts =+ ( ) - max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs _______________________________________________________________________________________ 9 +3.3v pwm 18k ? 27k ? 10k ? 120k ? +3.3v +12v 500k ? v out to fan 1 f 1 f 0.01 f 0.1 f figure 5. driving a fan with a pwm-to-dc circuit v cc pwm 4.7k ? 5v figure 6. controlling a pwm input fan with the max6615/ max6616s?pwm output (typically, the 35khz pwm frequency is used)
max6615/max6616 the duty cycle returns to either 0% or the fan-start duty cycle. the value of the hysteresis is set by d7 of the fan-configuration register. the duty cycle is limited to the value in the fan maximum duty-cycle register. if the duty-cycle value is larger than the maximum fan duty cycle, it is set to the maximum fan-duty cycle as in the fan maximum duty-cycle register. the temperature step is bit d6 of the fan-configuration register (0dh). notice if temperature crosses fanstarttemperature going up with an initial dutycycle of zero, a spin-up of 2s applies before the duty-cycle calculation controls the value of the fan? duty cycle. fanstarttemperature for a particular channel follows the channel, not the fan. if dutycycle is an odd number, it is automatically rounded down to the closest even number. duty-cycle rate-of-change control to reduce the audibility of changes in fan speed, the rate of change of the duty cycle is limited by the values set in the duty-cycle rate-of-change register. whenever the target duty cycle is different from the instantaneous duty cycle, the duty cycle increases or decreases at the rate determined by the duty-cycle rate-of-change byte until it reaches the target duty cycle. by setting the rate of change to the appropriate value, the thermal requirements of the system can be balanced against good acoustic performance. slower rates of change are less noticeable to the user, while faster rates of change can help minimize temperature variations. remember that the fan controller is part of a complex control system. because several of the parameters are generally not known, some experimentation may be necessary to arrive at the best settings. fan-fail when the fan tachometer count is larger than the fan tachometer limit, the fan is considered failing. the max6615/max6616 pwm_ drives the fan with 100% duty cycle for about 2s immediately after detecting a fan-fail. at the end of that period, another measurement is initiated. if the fan fails both measurements, the fan_fail bit, as well as the fan_fail output, assert if the pin is not masked. if the fan fails only the first mea- surement, the fan goes back to normal settings. if one fan fails, it can be useful to drive the other fan with 100% duty cycle. this can be enabled with bit d0 of the fan-status register (1ch). slave addresses the max6615/max6616 appear to the smbus as one device having a common address for both adc chan- nels. the devices?address can be set to one of nine different values by pinstrapping add0 and add1 so that more than one max6615/max6616 can reside on the same bus without address conflicts (see table 2). the address input states are checked regularly, and the address data stays latched to reduce quiescent supply current due to the bias current needed for high- impedance state detection. power-on defaults at power-on, or when the por bit in the configuration byte register is set, the max6615/max6616 have the default settings indicated in table 3. some of these set- tings are summarized below: temperature conversions are active. channel 1 and channel 2 are set to report the remote temperature channel measurements. channel 1 ot limit = +110?. channel 2 ot limit = +80?. manual fan mode. fan-start duty cycle = 0. pwm invert bit = 1. dual-channel temperature monitors and fan-speed controllers with thermistor inputs 10 ______________________________________________________________________________________ fan-start duty cycle temperature duty cycle register 02h, bit d3 = 1 duty-cycle step size fan-start temperature temp step register 02h, bit d3 = 0 figure 7. automatic pwm duty control
gpio inputs/outputs and preset (max6616) the max6616 has six gpio ports. gpio0 has a por control pin (preset). when preset is connected to gnd at por, gpio0 is configured as an output and is low. when preset is connected to v cc at por, gpio0 is configured as an input. since gpio0 is a high- impedance node in this state, it can be connected to a pullup resistor and also serve as an output (high). the rest of the gpio ports, gpio5?pio1, are configured as high-impedance outputs after power-on, so they will be in the high state if connected to pullup resistors. all gpios are at their preset values within 1ms of power- up. during power-up, gpio1 and gpio2 are low while the remaining gpios go into high-impedance state. figure 8 shows the states of the gpio lines during power-up. after power has been applied to the max6616, the gpio functions can be changed through the smbus interface. register descriptions the max6615/max6616 contain 32/34 internal regis- ters. these registers store temperature data, allow con- trol of the pwm outputs, determine if the devices are measuring from the internal die or the thermistor inputs, and set the gpio as inputs or outputs. temperature registers (00h and 01h) the temperature registers contain the results of temper- ature measurements. the value of the msb is 128? and the value of the lsb is 1?. temperature data for ther- mistor channel 1 is in the temperature channel 1 register (00h). temperature data for thermistor channel 2 (01h) or the local sensor (selectable by bit d2 in the configura- tion byte) is in the temperature channel 2 register. configuration byte (02h) the configuration byte register controls timeout condi- tions and various pwm signals. the por state of the configuration byte register is 18h. see table 4 for con- figuration byte definitions. channel 1 and channel 2 o o t t limits (03h and 04h) set channel 1 (03h) and channel 2 (04h) temperature thresholds with these two registers. once the temperature is above the threshold, the ot output is asserted low (for the temperature channels that are not masked). the por state of the channel 1 ot limit register is 6eh, and the por state of the channel 2 ot limit register is 50h. o o t t status (05h) a 1 in d7 or d6 indicates that an ot fault has occurred in the corresponding temperature channel. only read- ing its contents clears this register. reading the con- tents of the register also clears the ot output. if the fault is still present on the next temperature measure- ment cycle, the bits and the ot output are set again. the por state of the ot status register is 00h. o o t t mask (06h) set bit d7 to 1 in the ot mask register to prevent the ot output from asserting on faults in channel 1. set bit d6 to 1 to prevent the ot output from asserting on faults in channel 2. the por state of the ot mask reg- ister is 00h. pwm start duty cycle (07h and 08h) the pwm start duty-cycle register determines the pwm duty cycle where the fan starts spinning. bit d2 in the configuration byte register (min duty cycle) deter- mines the starting duty cycle. if the min duty cycle bit is 1, the duty cycle is the value written to the fan- start duty-cycle register at all temperatures below the fan-start temperature. if the min duty cycle bit is max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs ______________________________________________________________________________________ 11 table 2. slave address decoding (add0 and add1) addo add1 address gnd gnd 0011 000 gnd high-impedance 0011 001 gnd v cc 0011 010 high-impedance gnd 0101 001 high-impedance high-impedance 0101 010 high-impedance v cc 0101 011 v cc gnd 1001 100 v cc high-impedance 1001 101 v cc v cc 1001 110 note: high-impedance means that the pin is left unconnected and floating. por (internal) v cc gpio0 gpio1, gpio2 gpio3, gpio4, gpio5 high-impedance state state determined by preset high-impedance state 1ms figure 8. power-on gpio states
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs 12 ______________________________________________________________________________________ table 3. register map r/ w add por state function d7 d6 d5 d4 d3 d2 d1 d0 r 00h 0000 0000 temperature channel 1 msb (128?) lsb (1?) r 01h 0000 0000 temperature channel 2 msb (128?) lsb (1?) r/ w 02h 0001 1000 c onfi g ur ati on b yte standby: 0 = run; 1 = standby por: 1 = reset timeout: 0 = enabled; 1 = disabled fan 1 pwm invert fan 2 pwm invert min duty cycle: 0 = 0%; 1 = fan-start duty cycle temp ch2 sources: 1 = local; 0 = remote2 spin-up disable: 0 = enable; 1 = disable r/ w 03h 0110 1110 temperature channel 1 ot limit msb lsb (1?) r/ w 04h 0101 0000 temperature channel 2 ot limit msb lsb (1?) r 05h 00xx xxxx ot status c hannel 1: 1 = faul t c hannel 2: 1 = faul t r/ w 06h 00xx xxxx ot mask c hannel 1: 1 = m asked channel 2: 1 = masked r/ w 07h 0110 000x 96 = 40% pwm1 start duty cycle msb (128/240) lsb (2/240) r/ w 08h 0110 000x 96 = 40% pwm2 start duty cycle msb (128/240) lsb (2/240) r/ w 09h 1111 000x 240 = 100% pwm1 max duty cycle msb (128/240) lsb (2/240) r/ w 0ah 1111 000x 240 = 100% pwm2 max duty cycle msb (128/240) lsb (2/240) r/ w 0bh 0000 000x pwm1 target duty cycle msb (128/240) lsb (2/240) r/ w 0ch 0000 000x pwm2 target duty cycle msb (128/240) lsb (2/240)
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs ______________________________________________________________________________________ 13 table 3. register map (continued) r/ w add por state function d7 d6 d5 d4 d3 d2 d1 d0 r 0dh 0000 000x pwm1 instantan- eous duty cycle msb (128/240) lsb (2/240) r 0eh 0000 000x pwm2 instantan- eous duty cycle msb (128/240) lsb (2/240) r/ w 0fh 0000 0000 channel 1 fan-start temperature msb lsb r/ w 10h 0000 0000 channel 2 fan-start temperature msb lsb r/ w 11h 0000 000x fan configuration hysteresis: 0 = 5?, 1 = 10? temp step : 0 = 1c, 12c fan 1: control 1 = ch 1 fan 1: control 1 = ch 2 fan 2: control 1 = ch 1 fan 2: control 1 = ch 2 r/ w 12h 1011 01xx duty-cycle rate of change fan 1 msb fan 1 lsb fan 2 msb fan 2 lsb r/ w 13h 0101 0101 duty-cycle step size fan 1 msb fan 1 lsb fan 2 msb fan 2 lsb r/ w 14h 010x xxxx pwm frequency select select a select b select c r/ w 15h xx00 000* gpio function gpio5: 0 = output; 1 = input gpio4: 0 = output; 1 = input gpio3: 0 = output; 1 = input gpio2: 0 = output; 1 = input gpio1: 0 = output; 1 = input gpio0: 0 = output; 1 = input r/ w 16h xx11 111* ( n ote 1) gpio value gpio5 gpio4 gpio3 gpio2 gpio1 gpio0 r/ w 17h 0000 0000 thermistor offset register th1 msb (sign) th1 lsb (2?) th2 msb (sign) th2 lsb (2?) r 18h 1111 1111 tach1 value register r 19h 1111 1111 tach2 value register r/ w 1ah 1111 1111 tach1 limit register r/ w 1bh 1111 1111 tach2 limit register
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs 14 ______________________________________________________________________________________ table 3. register map (continued) r/ w add por state function d7 d6 d5 d4 d3 d2 d1 d0 r/ w 1ch 0000 0000 fan status byte 1 = fan 1 failure 1 = fan 2 failure 1 = disabled fan 1 tach 1 = disabled fan 2 tach 1 = measure fan 1 when it is full speed 1 = measure fan 2 when it is full speed 1 = m ask fan_fail p i n 1 = fan 1 fail sets fan 2 100% r 1eh 0000 0000 channel 1 temp lsbs msb (1/2?) lsb (1/8?) r 1fh 0000 0000 channel 2 temp lsbs msb (1/2?) lsb (1/8?) r fdh 0000 0001 read device revision 00000001 r feh 0110 1000 read device id 01101000 r ffh 0100 1101 read m anufactur er id 01001101 * gpio0 por values are set by preset. table 4. configuration byte definition (02h) bit name por state function 7 run/standby 0 set to zero for normal operation. set to 1 to suspend conversions and pwm outputs. 6 por 0 set to 1 to perform reset of all device registers. 5 timeout 0 set timeout to zero to enable smbus timeout for prevention of bus lockup. set to 1 to disable this function. 4 fan1 pwm invert 1 set fan pwm invert to zero to force pwm1 low when the duty cycle is 100%. set to 1 to force pwm1 high when the duty cycle is 100%. 3 fan2 pwm invert 1 set fan pwm invert to zero to force pwm2 low when the duty cycle is 100%. set to 1 to force pwm2 high when the duty cycle is 100%. 2 min duty cycle 0 set min duty cycle to zero for a 0% duty cycle when the measured temperature is below the fan-temperature threshold in automatic mode. when the temperature equals the fan- temperature threshold, the duty cycle is the value in the fan-start duty-cycle register, and it increases with increasing temperature. set min duty cycle to 1 to force the pwm duty cycle to the value in the fan-start duty-cycle register when the measured temperature is below the fan-temperature threshold. as the temperature increases above the temperature threshold, the duty cycle increases as programmed. 1 temperature source select 0 selects either local or remote 2 as the source for temperature channel 2 register data. when d1 = 0, the max6615/max6616 measure remote 2 and when d1 = 1, the max6615/max6616 measure the internal die temperature. 0 spin-up disable 0 set spin-up disable to 1 to disable spin-up. set to zero for normal fan spin-up.
zero, the duty cycle is zero below the fan-start tempera- ture and has this value when the fan-start temperature is reached. a value of 240 represents 100% duty cycle. writing any value greater than 240 causes the fan speed to be set to 100%. the por state of the fan-start duty-cycle register is 60h, 40%. pwmout max duty cycle (09h and 0ah) the pwm maximum duty-cycle register sets the maxi- mum allowable pwm duty cycle between 2/240 (0.83% duty cycle) and 240/240 (100% duty cycle). any values greater than 240 are recognized as 100% maximum duty cycle. the por state of the pwm maximum duty- cycle register is f0h, 100%. in manual-control mode, this register is ignored. pwm target duty cycle (0bh and 0ch) in automatic fan-control mode, this register contains the present value of the target pwm duty cycle, as deter- mined by the measured temperature and the duty- cycle step size. the actual duty cycle requires time before it equals the target duty cycle if the duty-cycle rate-of-change register is set to a value other than zero. in manual fan-control mode, write the desired value of the pwm duty cycle directly into this register. the por state of the fan-target duty-cycle register is 00h. pwm1 instantaneous duty cycle, pwm2 instantaneous duty cycle (0dh, 0eh) these registers always contain the duty cycle of the pwm signals presented at the pwm output. the por state of the pwm instantaneous duty-cycle register is 00h. channel 1 and channel 2 fan-start temperature (0fh and 10h) these registers contain the temperatures at which fan control begins (in automatic mode). see the automatic pwm duty-cycle control section for details on setting the fan-start thresholds. the por state of the channel 1 and channel 2 fan-start temperature registers is 00h. fan configuration (11h) the fan-configuration register controls the hysteresis level, temperature step size, and whether the remote or local diode controls the pwm2 signal (see table 3). set bit d7 of the fan-configuration register to zero to set the hysteresis value to 5?. set bit d7 to 1 to set the hys- teresis value to 10?. set bit d6 to zero to set the fan- control temperature step size to 1?. set bit d6 to 1 to set the fan-control temperature step size to +2?. bits d5 to d2 select which pwm_ channel 1 or channel 2 controls (see table 3). if both are selected for a given pwm_, the highest pwm value is used. if neither is selected, the fan is controlled by the value written to the fan-target duty-cycle register. also in this mode, the value written to the target duty-cycle register is not limited by the value in the maximum duty-cycle register. it is, howev- er, clipped to 240 if a value above 240 is written. the por state of the fan-configuration register is 00h. duty-cycle rate of change (12h) bits d7, d6, and d5 (channel 1) and d4, d3, and d2 (channel 2) of the duty-cycle rate-of-change register set the time between increments of the duty cycle. each increment is 2/240 of the duty cycle (see table 5). this allows the time from 33% to 100% duty cycle to be adjusted from 5s to 320s. the rate-of-change control is always active in manual mode. to make instant changes, set bits d7, d6, and d5 (channel 1) or d4, d3, and d2 (channel 2) = 000. the por state of the duty-cycle rate- of-change register is b4h (1s between increments). max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs ______________________________________________________________________________________ 15 table 5. setting the time between duty- cycle increments d7:d5, d4:d2 time between increments (s) time from 33% to 100% (s) 000 0 0 001 0.0625 5 010 0.125 10 011 0.25 20 100 0.5 40 101 1 80 110 2 160 111 4 320 table 6. setting the duty-cycle step size d7:d4, d3:d0 change in duty cycle per temperature step temperature range for fan control (1 c step, 33% to 100%) 0000 0 0 0001 2/240 80 0010 4/240 40 0011 6/240 27 0100 8/240 20 0101 10/240 16 ... 1000 16/240 10 ... ... ... 1111 31/240 5
max6615/max6616 duty-cycle step size (13h) bits d7?4 (channel 1) and bits d3?0 (channel 2) of the duty-cycle step-size register change the size of the duty- cycle change for each temperature step. the por state of the duty-cycle step-size register is 55h (see table 6). pwm frequency select (14h) set bits d7, d6, and d5 (select a, b, and c) in the pwm frequency-select register to control the pwm frequency (see table 7). the por state of the pwm frequency- select register is 40h, 33hz. the lower frequencies are usually used when driving the fan? power-supply pin as in the typical application circuit , with 33hz being the most common choice. the 35khz frequency setting is used for controlling fans that have logic-level pwm input pins for speed control. the minimum duty-cycle resolution is decreased from 2/240 to 4/240 at the 35khz frequen- cy setting. for example, a result that would return a value of 6/240 is truncated to 4/240. gpio function register (15h) (max6616) the gpio function register (15h) sets the gpio states. write a zero to set a gpio as an output. write a 1 to set a gpio as an input. gpio value register (16h) (max6616) the gpio value register (16h) contains the state of each gpio input when a gpio is configured as an input. when configured as an output, write a 1 or zero to set the value of the gpio output. thermistor offset register (17h) the thermistor offset register contains the offset for both of the thermistors in two? complement. bits d7, d6, d5, and d4 set the offset for temperature channel 1. bits d3, d2, d1, and d0 set the offset for temperature chan- nel 2. the values in this register allow the thermistor temperature readings to be shifted to help compensate for different thermistor characteristics or different values of r ext and apply to thermistor measurements only. the msb is the sign bit and the lsb is 2?. the por state for this register is 00h. tachometer value registers (18h and 19h) the tachometer value registers contain the tachometer count values for each fan. the max6615/max6616 measure the tachometer signal every 67s. it counts the number of clock cycles between two tachometer pulses and stores the value in the corresponding channel reg- ister. the por state of this register is ffh. tachometer limit registers (1ah and 1bh) the tachometer limit registers contain the tachometer limits for each fan. if the value in the tach1 value regis- ter (18h) ever exceeds the value stored in 1ah, a chan- nel 1 fan failure is detected. if the value in the tach2 value register (19h) ever exceeds the value stored in 1bh, a channel 2 fan failure is detected. the por state of these registers is ffh. fan configuration/status register (1ch) the fan configuration/status register contains the status and tachometer control bits for both fans. bits d7 and d6 indicate whether a fan has failed the maximum tachometer limits in registers 1ah and 1bh. setting bits d5 and d4 disables the tachometer for each fan. the speed is not measured when these bits are set. setting bits d3 and d2 measure the fan speed only during spin-up or when it reaches 100% duty cycle. bit d1 is the fan_fail output mask. bit d0 is the fan_fail cross drive enable. setting this bit enables fan 2 to go to full speed when fan 1 fails or vice versa. extended temperature registers (1eh and 1fh) the extended temperature registers contain the low-byte results of temperature measurements. the value of the msb is 0.5? and the value of d5 is 0.125?. the por states of these registers are 00h. dual-channel temperature monitors and fan-speed controllers with thermistor inputs 16 ______________________________________________________________________________________ table 7. pwm frequency select pwm frequency (hz) select a select b select c 20 000 33 010 50 100 100 1 1 0 35k x x 1 note: at 35khz, duty-cycle resolution is decreased from a res- olution of 2/240 to 4/240.
applications information thermistor considerations ntc thermistors are resistive temperature sensors whose resistance decreases with increasing tempera- ture. they are available in a wide variety of packages that are useful in difficult applications such as measure- ment of air or liquid temperature. some can operate over temperature ranges beyond that of most ics. the relationship between temperature and resistance in an ntc thermistor is very nonlinear and can be described by the following approximation: where t is absolute temperature in kelvin, r is the ther- mistor? resistance, and a, b, and c are coefficients that vary with manufacturer and material characteristics. the highly nonlinear relationship between temperature and resistance in an ntc thermistor makes it somewhat more difficult to use than a digital-output temperature- sensor ic. however, by connecting the thermistor in series with a properly chosen resistor and using the max6615/max6616 to measure the voltage across the resistor, a reasonably linear transfer function can be obtained over a limited temperature range. accuracy increases over smaller temperature ranges. figures 9 and 10 show a good relationship between temperature and data. this data was taken using a popular thermistor model, the betatherm 10k3a1, with r ext = 1.6k ? . using these values produces data with good conformance to real temperature over a range of about +30? to +100?. different combinations of ther- mistors and r ext result in different curves. adc noise filtering the integrating adc has inherently good noise rejec- tion, especially at low-frequency signals such as 60hz/120hz power-supply hum. lay out the pcb care- fully with proper external noise filtering for high-accura- cy thermistor measurements in electrically noisy environments. filter high-frequency electromagnetic interference (emi) at th_ and ref with an external 100pf capacitor connected between the two inputs. this capacitor can be increased to about 2000pf (max), including cable capacitance. a capacitance higher than 2000pf intro- duces errors due to the rise time of the switched cur- rent source. chip information process: bicmos 1 3 t a b in r c in r =+ + () [()] max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs ______________________________________________________________________________________ 17 max6615/max6616 error -12 -10 -6 -8 0 2 -2 -4 4 error ( c) 04060 20 80 100 120 140 temperature ( c) optimized for +30 c to +100 c figure 9. data error vs. temperature using a betatherm 10k3a1 thermistor 0 40 20 80 60 100 120 -50 50 0 100 150 measurement vs. temperature temperature ( c) measurement ( c) figure 10. measured temperature vs. actual temperature
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs 18 ______________________________________________________________________________________ v cc v fan v cc v fan (5v or 12v) v fan 3.0v to 5.5v thermistor betatherm 10k3a1 max6615 th1 4.7k ? 10k ? 10k ? ref 100pf 100pf th2 1.6k ? 1.6k ? sda scl ot tach1 tach2 pwm2 pwm1 fan_fail v cc gnd(10) gnd(5) add0 add1 to clock throttle or system shutdown v fan (5v or 12v) 4.7k ? thermistor to smbus master betatherm 10k3a1 typical application circuits 24 23 22 21 20 19 18 17 1 2 3 4 5 6 7 8 v cc scl sda pwm2 ot tach1 pwm1 gpio5 tach2 gpio4 gpio3 preset gnd ref add1 add0 gpio2 gpio1 gpio0 16 15 14 13 9 10 11 12 fan_fail n.c. n.c. th1 th2 max6616 qsop 1 2 3 4 5 6 7 8 v cc scl sda pwm2 ot tach1 pwm1 top view tach2 gnd gnd ref add1 add0 16 15 14 13 9 10 11 12 fan_fail th1 th2 max6615 qsop pin configurations
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs ______________________________________________________________________________________ 19 v cc v cc v cc v cc v fan v cc v fan (5v or 12v) v fan 3.0v to 5.5v thermistor betatherm 10k3a1 max6616 th1 4.7k ? 10k ? 10k ? 10k ? 10k ? 10k ? ref 100pf 100pf th2 1.6k ? 1.6k ? sda scl gpio2 gpio1 gpio0 preset gpio5 gpio4 gpio3 ot tach1 tach2 pwm2 pwm1 fan_fail v cc gnd add0 add1 to clock throttle or system shutdown v cc v cc v cc 10k ? 10k ? 10k ? v fan (5v or 12v) 4.7k ? thermistor to smbus master betatherm 10k3a1 typical application circuits (continued) package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . package type package code document no. 16 qsop e16-1 21-0055 24 qsop e24-1 21-0055
max6615/max6616 dual-channel temperature monitors and fan-speed controllers with thermistor inputs 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. 20 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 initial release 1 7/05 2 10/08 specified por values for registers that were inconsistent with table 3. 10, 15, 16

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