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?2004 fairchild semiconductor corporation www.fairchildsemi.com rev.1.0.3 features ? output direct pwm drive for speed control selectable pwm frequency : internal or external versatile speed control inputs: a thermistor or pwm input. a wide range of operating voltage: 3.2v to 28v locked rotor protection with open collector output and auto retry open collector hall ou tput for speed feedback adjustable minimum speed thermistor disconnection protection tsd protection. description the FAN8460MTC/fan8460mp is a single phase bldc motor driver with variable speed control using output direct pwm method and it?s typical application is dc cooling fans with wide range of supply voltage(5/12/24v). this approach eliminates the need for external pass devices such as bjt, mosfet. this solution also offers other advantages over commonly used external pwm turning fan?s power on and off at fixed frequency. the external pwm increas stress on fan and needs level translati on in speed and alarm output because these outputs share the fan?s negative terminal. in case of cpu cooling, digital controller can give speed control command with pwm signal adjusting the duty. if a system has no digital controller, the ntc thermistor input mechanism can control fan speed with local or ambient tem- perature sensing.these two kinds of input schemes can meet various system requirements and applications. 14-mlp 4x4 14-tssop typical applications cpu cooling fans instrumentation fans desktop pc fans ordering information device package operating temp. FAN8460MTC 14-tssop ? 30 c ~ 90 c FAN8460MTCx 14-tssop ? 30 c ~ 90 c fan8460mpx 14-mlp 4x4 ? 30 c ~ 90 c FAN8460MTC/fan8460mp single phase full wave bldc motor driver with variable speed control
FAN8460MTC/fan8460mp 2 block diagram commutation & control & tsd lock detection & auto restart 2v reference switching control triangle wave generator v ldcp v ldcl vs s pwm 5 11 3 1 2 14 4 outa outb vs gnd vcon vref ld h+ h- taco ct vpwm pwm 6 8 13 al 12 7 10 vm 9 i pwm pwm decoder
FAN8460MTC/fan8460mp 3 pin definitions pin number pin name i/o pin function description remark 1h ? a hall input - 2h + a hall input + - 3lda sawtooth wave generator for lock detector and automatic restart - 4 vref a reference voltage output 5 vpwm i pwm input for speed control - 6 outa a motor output a - 7gndpground - 8 outb a motor output b - 9 vm p power supply for output stage - 10 vs p power supply for signal block 11 vcon a speed control signal 12 ct a triangle waveform out - 13 al o alarm output open collector 14 taco o speed output open collector
FAN8460MTC/fan8460mp 4 absolute maximum ratings (ta = 25 c) note : 1. refer: eia/jesd 51-2 & eia/jesd 51-3 & eia/jesd 51-5 & eia/jesd 51-7 2. case 1: single layer pcb with 1 signal plane only, pcb size 76mm 114mm 1.6mm. 3. case 2: multi layer pcb with 1 signal, 1 power and 1 ground planes, pcb size 76mm 114mm 1.6mm, cu plane sizes for power and ground 74mm 74mm 0.035mm, thermal via hole pitch 0.9mm, via hole size 0.3mm, 6 via hole. 4. should not exceed p d or aso value. 5. i opeak time is within 2us. parameter symbol value unit maximum power supply voltage vs max, vm max 32 v thermal resistance rja 143 (FAN8460MTC) o c/w 150 (fan8460mp case1) o c/w 45 (fan8460mp case2) o c/w maximum power dissipation p dmax 870 (FAN8460MTC) mw 800 (fan8460mp case1) mw 2700 (fan8460mp case2) mw maximum output voltage v omax 36 v maximum output current i omax 0.8 note a maximum output peak current i opeak 1.2 note a maximum taco/alarm output current i taco/al 5ma taco/alarm output sustain voltage v taco/al 36 v hall output withstanding voltage v ho 36 v vpwm input voltage v vpwm -0.3~ vs v operating temperature t opr ? 30 ~ 90 c storage temperature t stg ? 55 ~ 150 c case 1 case 2 remark pd is measured base on the je- dec/std(jesd 51-2) pd= 0.8w pd= 2.7w pcb(glass-epoxy) power plane(cu) plane(cu) gnd via
FAN8460MTC/fan8460mp 5 power dissipation curve recommended operating conditions (ta = 25 c) parameter symbol min. typ. max. unit supply voltage for signal block vs 3.2 ? 28 v supply voltage for output stage vm 3.2 ? 28 v 175 150 125 100 50 25 0 1,000 2,000 3,000 pd [mw] ambient temperature, ta [ c] 0 75 case2 14tssop soa case1
FAN8460MTC/fan8460mp 6 equivalent circuits description pin no. internal circuit hall input 1 , 2 ld 3 output 6 , 8 al/taco 13 , 14 vcc 1 2 3 v cc vm 6 8 1 3 1 4
FAN8460MTC/fan8460mp 7 equivalent circuits description pin no. internal circuit vpwm 5 vcon/ct 11/12 5 reference vcc 11 1 2
FAN8460MTC/fan8460mp 8 FAN8460MTC/fan8460mp elec trical characteristics (ta = 25 c, v s = 12v unless otherwise specified) parameter symbol conditions min. typ. max. unit common block supply current i cc -4.5 7ma reference output voltage v ref1 iref=200ua 1.85 2.0 2.15 v reference output voltage v ref2 iref=2ma 1.75 1.94 2.13 v lock detector & auto restart ld charging current i ldc v ld =0v-->1.5v ,v ld =1.5v 1.4 2.2 2.9 a ld discharging current i ldd v ld =3v-->1.5v ,v ld =1.5v 0.15 0.33 0.50 a ld clamp voltage v ldcl -2.32.62.9v ld comparator voltage v ldcp -0.40.60.8v triangle wave generator ct discharging current i ctd v ct =2.0v-->1.2v,v ct =1.2v -7.2 -6 -4.8 a ct charging current i ctc v ct =0.5v-->1.2v,v ct =1.2v 4.8 6 7.2 a ct valley voltage v ctmin - 0.71 0.8 0.89 v ct peak voltage v ctmax -1.71.81.9v speed control voltage vcon output current i vcon v vcon =2v, pwm=h 180 200 220 a output off vcon low voltage v conl - - 300 mv vpwm input vpwm low voltage v pwml -0.5v vpwm high voltage v pwmh 2.8 - - v vpwm input current i pwml v vpwm =5v - 70 100 a output stage high side output saturation voltage v osh i o =200ma - 0.9 1.1 v low side output saturation voltage v osl i o =200ma 0.2 0.3 v speed output (taco) & lock detection output (al) taco output saturation voltage v tacos i taco =5ma - 0.1 0.3 v taco output leakage current i taco v taco =12v - 0.1 10 a al output saturation voltage v als i al =5ma - 0.1 0.3 v al output leakage current i al v al =12v - 0.1 10 a hall amplifier input range v hdc -0-v s -2.8 v input offset v hof --10-10mv
FAN8460MTC/fan8460mp 9 application information 1 direct output pwm for fan motor speed control direct output pwm method is used to control driving power to a fan motor and thus fan motor speed. a motor current, and thus fan motor speed is proportional to duty-cycle of ou tput pwm signal in FAN8460MTC/fan8460mp. the internal pwm signal is driven by comparing a triangle wave (pwm oscillator output, v ct ) and a control dc voltage v vcon ). figure.1 illustrates the relationships among oscillator output (v ct ), speed control voltage (v vcon ), motor current, and output pwm duty. figure 1. basic speed control concept . figure 2. the relationship between speed control voltage and output pwm duty as shown in figure2, the output pwm duty-cycle can be decreased as v vcon is increased. the effective range of speed con- trol voltage (v vcon ) is 0.8 ~1.8v(typical) which represents a duty- cycle range of 0% to 100% on pwm signal.when v vcon is 1.3v, the output pwm duty becomes 50%. 2 h-bridge motor driver (outa, outb) using an h-bridge to drive a single-phase bldc motor provides several advantages for dc fans over a two phase motor com- monly driven by two commutated low-side switches. a single phase motor has only two connections; hence, the h-bridge topology requires only two outp ut terminals and two traces are needed on the fan pcb. generally , this h-bridge method with single phase motor increases fan motor torque density over a typi cal unipolar drive method. in addition, the h-bridge topology eliminates the number of extern al component for snubbing and allo ws recirculation of winding cu rrent to maintain energy in a t pwm t on t off v ct v vcon i m high speed low speed mid speed v vcon v ct i m(avg) i m i freewheeling 0 .8v 1 .8v pwm speed control voltage(v vcon ) 50% 100% 0 0.8v 1.8v 1.3v o utput pwm(duty) 2v
FAN8460MTC/fan8460mp 10 motor while pwm switching occurs. pwm occurs on the high si de, and the freewheeling current flow on the low side during t off . 3 triangle waveform generator (pwm oscillator) the pwm oscillator output (v ct ) sets output pwm frequency using external capacitor (c t ). when v c t reaches the upper threshold(1.8v typical) by intern al current source( 6ua typical), c t begins to be discharged by internal current sink(-6ua typ- ical) until the low threshold(0.8v typical). it repeats the charging and discharging cycle. to have a desired pwm frequency, f ct , can be calculated as follows; for example, c t = 100pf, then f ct is about 25khz. 4. speed control voltage (v vcon ) and active filter (pwm decoder) in general, many pc super io and hardware monitoring ics pr ovide one of two fan speed control output to provide variable fan speed control without an external drive power stage. FAN8460MTC/fan8460mp have two type of input stage scheme. this means an end user can control the fan speed with a pwm si gnal or a dc control voltage (typically thermistor input). fig- ure.3 shows two kind of input stages; ambient temperature based input stage using thermis tor(figure.3a) and digital pwm input stage(figure.3b). figure 3. input stages and speed control voltage output 4.1 ntc thermistor based speed control(scheme 1) when the ambient temperature based speed control is used, the vpwm pin must be connected with ground as shown fig- ure.3a. the v vcon will be adjusted automatically by ambient temperature with ntc ther mistor. when the ambient tempera- ture increases, decreased thermist or resistance results in low v vcon and high fan motor speed. an optional resistor, r min, is set to a minimum speed when thermistor is accidentally disconnected. the v vcon is calculated as follows; for example, rpwm = 3k, rmin =open, rntc=10k, the v vcon is shown in fig4.a. when the temperature is higher than 65, motor will run at full speed. in case, the temperature is under 5 c , no drive will be present. but the practical motor stop temperature is slightly higher than 5 c because motor needs minimum starting torque depending on mechanics, motor size. in case, the rmin is not used, fan motor runs at full sp eed when the thermistor is accidentally disconnected. another example is useage of optinal resistor r min to limit minimum motor speed. for example, rpwm = 1.5k, rmin = 3.3k, rntc=10k, fig4.b shows the resultant vcon voltage is under 1.3v and thus the minimum pwm duty will be over 0.5. it means motor will runs at medium speed even if ntc is disconnected accidentally. c t i ctc 2f ct v ctmax v ctmin ? () ------------------------- ----------------------- -------------------- - = r ntc r pwm 2v reference 5 4 vcon vref vpwm pwm decoder vs 11 r min pwm decoder c pwm r pwm 2v reference 5 4 vcon vref vpwm 6.2k vs 11 120k r opt 12 ct 100pf 12 ct 1 00pf v vcon r min r ntc || () r min r ntc || () r pwm + ------------------------------------------------------------- - v vref =
FAN8460MTC/fan8460mp 11 figure 4. sensed temperatur e and speed control voltage 4.2 pwm speed control using internal oscillator(scheme 2) a digital pwm input applied to vpwm pin is converted to an alog dc voltage by pwm decoder and external rc filter. the external filter capacitor, c pwm , eliminates high freque ncy ac component in v vcon . if a large value of c pwm is used, v vcon has smaller value of ac component (ripple), bu t larger time delay can be occurred in v vcon with some fixed input frequency. the lower frequency of digita l pwm input needs the larger value of c pwm . external resistor r pwm, r pwm define the v vcon range as follow; figure 5. the relationship digital pwm input duty vs v vcon and output pwm duty for example, r pwm =6.2k and r opt =120k, v vcon become between 0.72v and 1.9v, because v vref =2v, i vocn = 200ua. for some design margin, under the 8% duty of digital pwm input, fan motor stops because the output pwm duty is 0. if the duty of digital pwm input is lager than 0.92, then output pwm duty is 100%. it means fan motor is operated in full speed. figure5.a shows the relationship between digital pwm input and active filter out (v vcon ) and figure5.b illustrates the 0 4 8 12 16 20 24 28 32 36 40 0 102030405060708090100 tem perature[c ] 10k ntc [ k ohm ] 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 vcon volta g e [ v ] 10k ohm ntc vc on v ol t age 0 4 8 12 16 20 24 28 32 36 40 0 10 20 30 40 50 60 70 8 0 9 0 10 0 tem perature[c] 10k ntc[kohm 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 vcon volta g e[v ] 10k ntc equi v alent resi stance vcon v ol tage v vcon on () v ref r pwm i vcon () ? {} r opt r opt r pwm + ---------------- --------------- - = v vcon off () v vref r opt r pwm r opt + () ? = digital vpwm input duty 50% 100% 0 output pwm(duty) 100% 0% 8% 88% 50% digital vpwm input duty 50% 100% 0 0.72v 1.9v v vcon (v) 8% 92% 0.8v 1.8v
FAN8460MTC/fan8460mp 12 output pwm duty is proportional to input pwm duty with some dead band. the output pwm frequency is defined by external capacitor, c t. so there is no relationship between vpwm input fr equency and output pwm frequency. table 1 summarizes the motor speed according to digital vpwm input and v vcon table 1. . operation tables 4.3 pwm speed control using external pwm input(scheme 3) this scheme indicates that digital pwm input signal becomes di rectly output pwm signal. in other word, frequency and duty of output pwm driving signal is the same as this digital pwm input. in case input pwm frequency is very low, active filter needs large value of capacitor to make speed control voltage in scheme 2. this scheme dosen?t need filter capacitor and has good input/output characteristics. this means that there is no deadband and output signals are synchronized with input vpwm signal as shown in figure6. figure 6. interface and it?s related waveforms scheme3 4.4 offset comparator(thermistor open protection) if under 100mv difference be tween vref and vcon, fan motor runs at full speed. 5 locked rotor protection with open collector output and automatic restart when the rotor is locked, there is no change in input signal of hall amplifier and thus a internal t zero pulse is not observed. a capacitor (c ld ) connected ld pin is co ntinually charged by in ternal current source (i ldc ) to the internal threshold (v ldcl ) resulting from no tzero pulse. when the voltage, v cld on ld pin, reaches v ldcl , high side output power tr is turned-off to protect motor during t off and the alarm output (al) beco mes floating high. when the v cld reaches upper threshold, v ldcl , v cld starts to decrease with internal current sink (i ldd ) to the low threshold, v ldcp . at that time, the v cld ramps up again and one of two outputs is turned on depending on locked rotor position during t on . the charging and discharging repeat until locked condition is removed, or FAN8460MTC/fan8460mp is powered down. the overall time chart is shown in figure.6. the auto- retry time (t on ), the motor protection time (t off ) and the locked rotor detection time (t lock ) are proportional to external capacitor, c ld. each value can be calculated as follows; mode vpwm vcon speed condition pwm input h l full speed lh stop h/l depend on mother board pwm signal proportional to pwm input duty thermistor input gnd depend on thermistor re sistance the higher temp, the faster fan speed r pwm 2v reference 5 4 vcon vref vpwm pwm decoder 6.2k vcc 11 h - h+ vpwm outa outb 20k 12 ct 180k
FAN8460MTC/fan8460mp 13 for example, c ld = 0.33uf, then t on= 0.3sec,t off= 2sec,t lock=0.4 sec. this al output can be used to info rm a locked rotor condition to super io or system co ntroller. because the al output is open coll ector type, end user can pull up this pin with a external resistor to the supply voltage of their choice (that is 5 or 3.3v). figure 7. overall timing chart t on c ld v ldcl v ldcp ? () i ldc ----------------------------------- --------------------- = t off c ld v ldcl v ldcp ? () i ldd ---------------------------------- ---------------------- = t lock c ld v ldcl i ldc ------------------------------ = h - h+ o utb o uta t aco al tzero n s n s n n s n s s n n s n s ld v ldcl v ldcp t on t off 1 rotation motor locked lock released rotor tlock
FAN8460MTC/fan8460mp 14 6. hall sensor amplifier figure 1. hall sensor interface the hall current (i h ) is determined as follows; where, rh is an external limiting resistor and ri is input impedance of hall sensor. an external capacitor, c h1 , can be used to reduce a power supply noise. c h2 can reduce the instant peak current using h-br idge?s commutation. the input range of hall amplifier is between 0v and v cc -2.8v as shown in following figure. figure 2. hall amplifier input range table 1. hall sensor output s and related pin outputs 7 open collector taco output for speed feedback the taco output comes from the hall ampl ifier output. because the taco output is op en collector type, end user can pull up this pin with a external resistor to the supply voltage of thei r choice (that is 5 or 3.3v). this resulting output signal has t wo pulses per revolution on a four pole motor. 9 supply voltage consideration a supply sustain capacitor (c r) should be placed as close to vm pin with gn d as layout permits. a reverse supply protection diode (d r ) prevent motor current from recirculating to power s ource when pwm operation and phase commutation occur. this results in increasing vm and vs pin voltage. this capacito r absorbs motor recirculating cu rrent and limits vm and vcc pin voltage. in general, large motor winding inductance and current n eed large value of c r. 9. thermal shutdown tsd on: two high side output tr are off.(typ. 175 c) tsd off: the circuit can be reactivated and begi n to operate in a normal condition. (typ. 150 c) (h+) - ( h-) ld out a out b al taco remark positive low level l pwm l l rotating negative low level pwm l l h ----hl or h lock FAN8460MTC fan8460mp h- h+ 1 2 v+ hall sensor c h2 rh ri c h1 i h v cc r h r i + () -------------------------- - = vs vs-2.8v vs / 2 gnd
FAN8460MTC/fan8460mp 15 typical application circuits 1 ( ntc thermistor based speed control ) mode vpwm vcon speed condition thermistor input gnd depend on thermistor resistance the higher temp, the faster fan speed r ntc hall v+ r pwm c t c ld v+ c r d r r h r 1 r 2 commutation & control & tsd lock detection & auto restart 2v reference switching control triangle wave generator v ldcp v ldcl vs s pwm 5 11 3 1 2 14 4 outa outb vs gnd vcon vref ld h+ h- taco ct vpwm pwm 6 8 13 al 12 7 10 vm 9 100pf i pwm pwm decoder > 0.47uf eletrolytic
FAN8460MTC/fan8460mp 16 typical application circuits 2 ( pwm input speed control using internal oscillator ) mode vpwm vcon speed condition pwm input h l full speed lh stop l/h h/l proportional to pwm du ty (duty range:0.15 ~ 0.85) hall v+ c pwm r pwm c ld c t v+ c r d r 6.2k r h r 1 r 2 100pf r opt commutation & control & tsd lock detection & auto restart 2v reference switching control triangle wave generator v ldcp v ldcl vs s pwm 5 11 3 1 2 14 4 outa outb vs gnd vcon vref ld h+ h- taco ct vpwm pwm 6 8 13 al 12 7 10 vm 9 i pwm pwm decoder > 0.47uf eletrolytic 120k
FAN8460MTC/fan8460mp 17 typical application circuits 3 ( pwm input speed control using external pwm input ) mode vpwm vcon speed condition pwm input h l full speed lh stop h/l l/h proportional to pwm duty hall v+ r pwm c ld v+ c r d r 6.2k r h r 1 r 2 20k commutation & control & tsd lock detection & auto restart 2v reference switching control triangle wave generator v ldcp v ldcl vs s pwm 5 11 3 1 2 14 4 outa outb vs gnd vcon vref ld h+ h- taco ct vpwm pwm 6 8 13 al 12 7 10 vm 9 i pwm pwm decoder > 0.47uf eletrolytic 180k
FAN8460MTC/fan8460mp 18 package dimensions (unit: mm) 14-tssop
FAN8460MTC/fan8460mp 19 package dimensions (unit: mm) 14-mlp 4x4
FAN8460MTC/fan8460mp 20 typical performance characreristics 0.00.10.20.30.40.50.60.7 0.0 0.5 1.0 1.5 2.0 2.5 vs=vm=12v low side tr saturation voltage high side tr saturation voltage vce[v] motor current[a] 0 5 10 15 20 25 30 3 4 5 vs current consumption icc[ma] vs[v] 012345 1.80 1.85 1.90 1.95 2.00 2.05 vs=12v vref load regulation vref[v] iref[ma] 0 5 10 15 20 25 30 1.5 1.6 1.7 1.8 1.9 2.0 iref=200ua vref line regulation vref[v] vs[v] 0 5 10 15 20 25 30 190 200 210 ivcon line regulation ivcon[ua] vs[v] 0 200 400 600 800 1000 0 5 10 15 20 25 24v at 57ohm 12v at 26ohm 5v at 13ohm 5v falling time 12v falling time 24v falling time 5v rising time 12v rising time 24v rising time supply voltage[v] time[ns]
FAN8460MTC/fan8460mp 21
FAN8460MTC/fan8460mp 9/13/04 0.0m 001 stock#dsxxxxxxxx ? 2002 fairchild semiconductor corporation life support policy fairchild?s products are not authorized for use as critical components in life support devices or systems without the express written approval of the president of fairchild semiconductor corporation. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain lif e, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. a critical component in an y component of a life support device or system whose fa ilure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com disclaimer fairchild semiconductor reserves the right to make changes with out further notice to any products herein to improve re liability, function or design. fairchild does not assume any liability arising out of the applic ation or use of any product or circuit described herein; neither does it convey any license under its pat ent rights, nor the rights of others.

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