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april 1997 preliminary ML4428 * sensorless smart-start? bldc pwm motor controller general description the ML4428 motor controller provides all of the functions necessary for starting and controlling the speed of delta or wye-wound brushless dc (bldc) motors without the need for hall effect sensors. back-emf voltage is sensed from the motor windings to determine the proper commutation phase sequence using pll techniques. the patented back-emf sensing technique used will commutate virtually any 3-phase bldc motor that has at least a 30% variation in inductance during rotation and is insensitive to pwm noise and motor snubbing circuitry. the ML4428 also utilizes a patented start-up technique which samples the rotor position and applies the proper drive to accelerate the motor. this ensures no reverse rotation at start-up and reduces total start-up time. features n stand-alone operation with forward and reverse n on-board start sequence: sense position ? drive ? accelerate ? set speed n no backward movement at start-up n patented back-emf commutation technique n simple variable speed control with on-board reference n single external resistor sets all critical currents n pwm control for maximum efficiency or linear control for minimum noise n 12v operation provides direct fet drive for 12v motors n drives high voltage motors with high side fet drivers n guaranteed no shoot-through when driving external fet gates directly * some packages are end of life block diagram/typical application 18 13 22 23 24 2 3 4 10 11 9 9v power fail back-emf sampler high side gate drive low side gate drive v flt vco phi1 phi2 phi3 p1 p2 p3 n1 n2 n3 28 gnd pwm current control and one shot 1 i sns 26 c ios start-up and commutation logic 17 c sns 25 brake 8 6v ref 7 27 pwm speed control v speed v ref r ref c pwm c sc 5 6 vco 16 15 r vco c vco 20 rc vco 14 v cc 12 f/ r 19 r init c isc 21 + C 0.6v run rev. 1.0 11/17/2000
ML4428 2 rev. 1.0 11/17/2000 pin configuration ML4428 28-pin molded narrow dip (p28n) 28-pin soic(s28) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 i sns p1 p2 p3 c sc c pwm v ref v speed n1 n2 n3 f/r vco v cc gnd r ref c ios brake phi3 phi2 phi1 c isc rc vco r init v flt c sns r vco c vco top view
ML4428 rev. 1.0 11/17/2000 3 pin description 1i sns motor current sense input. current limit one-shot is triggered when this pin is approximately 0.5v. 2 p1 drives the external p-channel transistor driving motor phi1. 3 p2 drives the external p-channel transistor driving motor phi2. 4 p3 drives the external p-channel transistor driving motor phi3. 5c sc the resistor/capacitor combination on this gm amplifier output sets a pole zero of the speed loop in conjunction with a gm of 0.230mmho. 6c pwm a capacitor to ground at this pin sets the pwm oscillator frequency. a 1nf capacitor will set the frequency to approximately 25khz for pwm speed control. grounding this pin selects linear speed control. 7v ref this voltage reference output (6v) can be used to set the speed reference voltage. 8v speed this voltage input to the amplifier in the speed loop controls the speed target of the motor. 9 n1 drives the external n-channel mosfets for phi1. 10 n2 drives the external n-channel mosfets for phi2. 11 n3 drives the external n-channel mosfets for phi3. 12 f/ r the forward/reverse pin controls the sequence of the commutation states and thus the direction of motor rotation. (ttl level) 13 vco this logic output indicates the commutation frequency of the motor in run mode. (ttl level) 14 v cc 12v power supply. 15 c vco timing capacitor for vco 16 r vco the resistor on this pin sets a process independent current to generate a repeatable vco frequency. 17 c sns this capacitor to ground sets the on time of the 6 sense pulses used for position detection at start-up and at low speeds. a 5.6nf capacitor will set the on time to approximately 200s. 18 v flt a logic 0 indicates the power supply is under-voltage. (ttl level) 19 r init this resistor sets the minimum vco frequency, and thus, the initial on time of the drive energization at start-up. a 2 my resistor to ground sets the minimum vco frequency to approximately 10hz, resulting in an initial drive energization pulse of 100ms in conjunction with 82nf c vco and 10k r vco . 20 rc vco vco loop filter components. 21 c isc a capacitor to ground at this gm amplifier output sets a pole in the current-mode portion of the speed loop in conjunction with a gm of 0.230mmho. 22 phi1 motor terminal 1 23 phi2 motor terminal 2 24 phi3 motor terminal 3 25 brake a 0 activates the braking circuit. (ttl level) 26 c ios a 50a current from this pin will charge a timing capacitor to gnd for fixed off-time pwm current control 27 r ref this resistor sets constant currents on the device to reduce process dependence and external components. a 120k resistor sets the previously mentioned current levels. 28 gnd signal and power ground pin name function pin name function
ML4428 4 rev. 1.0 11/17/2000 absolute maximum ratings absolute maximum ratings are those values beyond which the device could be permanently damaged. absolute maximum ratings are stress ratings only and functional device operation is not implied. supply voltage (pin 14) ............................................. 14v output current (pins 2, 3, 4, 9,10,11) ................... 50ma logic inputs (pins 12, 25) ................................ C0.3 to 7v junction temperature .............................................. 150c storage temperature range ..................... C65c to 150c lead temperature (soldering 10 sec.) ..................... 260c thermal resistance ( q ja ) plastic dip ....................................................... 52c/w plastic soic .................................................... 75c/w operating conditions temperature range commercial ............................................... 0c to 70c industrial ................................................ C40c to 85c v cc voltage .................................................... 12v 10% electrical characteristics unless otherwise specified, t a = 0c to 70c, v cc = 12v, r sns = 0.3y, c vco = 82nf, c ios = 100pf, r ref = 120ky, c sns = 5.6nf, r vco = 10k, r init = 2meg (notes 1, 2, and 3) symbol parameter conditions min typ max units oscillator (vco) frequency vs. v pin 20 rc vco = 2v 0c to 70c 550 600 750 hz/v C40c to 85c 520 600 750 hz/v maximum frequency rc vco = 6v 0c to 70c 1850 2150 2350 hz C40c to 85c 1650 2150 2350 hz sampling amplifier i rcvco (note 4) state a, v ph2 = vcc/3 80 116 150 a state a, v ph2 = vcc/2 C25 0 25 a state a, v ph2 = 2vcc/3 C150 C116 C80 a current limit i sns trip point 0.45 0.5 0.55 one shot off time 10 13 15 s power fail detection power fail trip voltage 8.0 9.0 v hysteresis 300 500 700 mv logic inputs v ih voltage high 2 v v il voltage low 0.8 v i ih current high v in = 2.7v C300 0 a i il current low v in = 0.4v C400 0 a logic outputs v oh voltage high i out = C0.1ma 3.3 v v ol voltage low i out = 1ma 0.4 v
ML4428 rev. 1.0 11/17/2000 5 electrical characteristics (continued) symbol parameter conditions min typ max units output drivers v p high i p = C10a v cc C 1.2 v v p low 0.7 1.2 v i p low v p = 1v 0c to 70c 2.5 4 6 ma C40c to 85c 1.5 4 6 ma p comparator threshold v cc C 3.0 v v n high v pin12 = 0v v cc C 1.2 v v n low i n = 1ma 0.7 1.2 v n comparator threshold 3v speed control f pwm c osc = 1nf 20 25 36 khz gm current 160 a csc positive clamp 2.9 3.1 3.35 v cisc positive clamp 5.2 5.5 5.6 v cisc negative clamp 1.2 1.7 1.9 v v ref 5.5 5.9 6.5 v supply v cc current 18 25 32 ma note 1: limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions. note 2: f/ r and brake have internal 17k w pull-up resistors to an internal 5v reference. note 3: v flt and vco have internal 4.3k w pull-up resistors to an internal 5v reference. note 4: for explanation of states, see figure 6 and table 1.
ML4428 6 rev. 1.0 11/17/2000 functional description the ML4428 provides closed-loop commutation for 3-phase brushless motors. to accomplish this task, a vco, integrating back-emf sampling error amplifier and sequencer form a phase-locked loop, locking the vco to the back-emf of the motor. the ic contains circuitry to control motor speed in pwm mode. braking and power fail detection functions are also provided on the chip. the ML4428 is designed to drive external power transistors (n-channel sinking transistors and p-channel sourcing transistors) directly. the ML4428 limits the motor current with a constant off- time pwm controlled current. the velocity loop is controlled with an on-board amplifier. an accurate, jitter- free vco output is provided equal to the commutation frequency of the motor. the ML4428 switches the gates of external n-channel power mosfets to regulate the motor current and directly drives the p-channel mosfets for 12v motors. the ML4428 ensures that there is no shoot through in any state of power drive to the fets. higher voltage motors can be driven using buffer transistors or standard high side drivers. speed sensing is accomplished by monitoring the output of the vco, which will be a signal which is phase-locked to the commutation frequency of the motor. back-emf sensing and commutator the ML4428 contains a patented back-emf sensing circuit (figure 1) which samples the phase which is not energized (shaded area in figure 2) to determine whether to increase or decrease the commutator (vco) frequency. a late commutation causes the error amplifier to charge the filter (rc) on r cvco , increasing the vco input while early commutation causes r cvco to discharge. the analog speed control loop uses r cvco as a speed feedback voltage. the input impedance of the three ph inputs is about 8.7ky to gnd. when operating with a higher voltage motor, the ph inputs should be divided down in voltage with series resistors so that the maximum voltage at any ph input does not exceed v cc . neutral 0 60 120 180 240 0 300 figure 2. typical motor phase waveform with back-emf superimposed (ideal commutation). figure 1. back-emf sensing block diagram neutral simulator f a + f b + f c 9 phi1 phi2 phi3 multiplexer r c1 c2 vco commutation logic sign changer b a C + loop filter i(rc) = va C vb 4.35k rc vco 2.9k 5.8k vco 22 23 24
ML4428 rev. 1.0 11/17/2000 7 res1, res2 and res3 operating motors at greater than 12v requires attenuation resistors in series with the sense inputs (phi1, phi2, phi3) to keep the voltage less than 12v. the phase sense input impedance is 8700y. this requires the external resistor to be set as follows and results in the given attenuation. res1 = res2 = res3 resi = 725 (v motor C 10) atten res = + 2900 1 8700 a larger value for res1 may be required if the peak motor phase voltage exceds v motor . isense filter the i sense filter consists of an rc lowpass filter in series with the current sense signal. the purpose of this filter is to filter out noise spikes on the current, which may cause false triggering of the one shot circuit. it is important that this filter not slow down the current feedback loop, or destruction of the output stage may result. the recommended values for this circuit are r = 1ky and c= 300pf. this gives a time constant of 300ns, and will filter out spikes of shorter duration. these values should suffice for most applications. if excessive noise is present on the i sense pin, the capacitor may be increased at the expense of speed of current loop response. the filter time constant should not exceed 500ns or it will have a significant impact on the response speed of the one shot current limit. cios the one shot capacitor determines the off time after the current limit is activated, i.e. the voltage on the i sense pin exceeded 0.5v. the following formula ensures that the motor current is stable in current limit: cv ios max motor () . = - 111 10 11 cios is in farads this is the maximum value that c ios should be. higher average torque during the current limit cycle can be achieved by reducing this value experimentally, while monitoring the motor current carefully, to be sure that a runaway condition does not occur. this runaway condition occurs when the current gained during the on time exceeds the current lost during the off time, causing the motor current to increase until damage occurs. for most motors this will not occur, as it is usually a self limiting phenomenon. (see figure 7) component selection guide in order to properly select the critical components for the ML4428 you should know the following things: 1. the motor operating voltage, v motor (v). 2. the maximum operating current for the motor, i max (a). 3. the number of poles the motor has, n. 4. the back-emf constant of the motor, k e (v s/rad). 5. the torque constant of the motor, k e (n m/a). (this is the same as the back-emf constant, only in different units.) 6. the maximum desired speed of operation, rpm max (rpm). 7. line to line resistance, r l-l (ohms). 8. line to line inductance, l l-l (henries). 9. the motor should have at least 15% line-to-line inductance variation during rotation for proper start- up sensing. (air core motors will not run using the ML4428.) examine the motor to determine if there is any iron in the core. if the stator coils are not wound around an iron form, the ml4425 or ml4426 may be a better choice. if you do not know one or more of the above values, it is still possible to pick components for the ML4428, but some experimentation may be necessary to determine the optimal value. all quantities are in si units unless other wise specified. the formulas in the following section are based on linear system models. the following formulas should be considered a starting point from which you can optimize your application. note: refer to application note 43 for details on loop compensation. rsense the function of r sense is to provide a voltage proportional to the motor current, for current limit/ feedback purposes. the trip voltage across r sense is 0.5v so: r i sense max = 05 . imax is the maximum motor current. the power dissipation in the resistor is i max squared times r sense , so the resistor should be sized appropriately. for very high current motors, a smaller resistor can be used, with an op-amp to increase the gain, so that power dissipation in the sense resistor is minimized.
ML4428 8 rev. 1.0 11/17/2000 cvco as given in the section on the vco and phase detector: c n rpm vco max = - 2931 10 6 where n is the number of poles in the motor, and rpm is the motors maximum operating speed in revolutions per minute. cpwm this capacitor sets the pwm ramp oscillator frequency. this is the pwm switching frequency. if this value is too low, <20khz, then magnetostriction effects in the motor may cause audible noise. if this frequency is too high, >30khz, then the switching losses in the output drivers may become a problem. 25khz should be a good compromise for this value, which can be obtained by using a 1nf capacitor. rvco and rref r vco should be 10k and r ref should be 120k for normal operation. vco filter see the section on the vco and phase detector for information on these components. vco and phase detector calculations the vco should be set so that at the maximum frequency of operation (the running speed of the motor) the vco control voltage will be no higher than v ref , or 6v. the vco maximum frequency will be: f n rpm max max = 005 . where n is the number of poles on the motor and rpm max is the maximum motor speed in revolutions per minute. the minimum vco gain derived from the specification table (using the minimum f vco at v vco = 6v) is: k c vco min vco () . = - 2 665 10 5 assuming that the v vco(max) = 5.5v, then c f vco max = - 5 5 2 665 10 5 .. or c n rpm vco max = - 2931 10 6 figure 4. back-emf phase locked loop components. r c1 c2 vco C + z rc rc vco f out k vco (hz/sec/v) gm = 0.23m sampled phase w bemf sampler rotor phase a/radian gm = 0.23ma/v ke w atten 2 p phase detector (r c2 s + 1) s (c2 + r c1 s c2 + c1) loop filter 2.665 10 C5 c vco s 2 p vco radian/sec/v v/a
ML4428 rev. 1.0 11/17/2000 9 figure 4 shows the linearized transfer function of the phase locked loop with the phase detector formed from the sampled phase through the gm amplifier with the loop filtered formed by r, c 1 , and c 2 . the phase detector gain is: ke atten a radian - w p 2 23 10 4 ./ where ke is the motor back-e.m.f. constant in v/radian/ sec, w is the rotor speed in r/s, and atten is the back- e.m.f. resistive attenuator, nominally 0.3. the simplified impedance of the loop filter is zs cs s s rc lead lag () () () = + + 1 1 w w where the lead and lag frequencies are set by: w lead rc = 1 2 w lag cc rc c = + 12 12 requiring the loop to settle in 20 pll cycles with w lag = 10 w lead produces the following calculations for r, c 1 and c 2 : c atten k n e 1 4 7 508 10 = - . c 2 = 9 c 1 r atten k rpm e max = 889 10 4 . where k e is the back-emf constant in volts per radian per second, and rpm max is the rotor speed. see micro linear application note 35 for derivation of the above formulas. the 80k resistor to gnd from the rc vco pin assists in a smooth transition from sense mode to closed loop operation. figure 5. typical sensed start-up t i motor drive sense drive sense drive drive sense loop closed here (run mode) t i motor ~200 m s drive ~100ms sense ~3ms figure 3. vco output frequency vs. vvco (pin 20) 024681012 3000 2500 2000 1500 1000 500 0 frequency (hz) vvco (volts) cvco = 164nf cvco = 82nf
ML4428 10 rev. 1.0 11/17/2000 csns a capacitor to ground at this pin sets the on time of the 6 current sense pulses used for position detection at start-up and at low speeds. the on time is set by: t on = c sns (35.7k) referring to figure 5, each of the 6 current sense pulses is governed by a rise time with a time constant of l/r where l is the inductance of the motor network with 2 windings shorted and r is the total resistance in series with the motor between the supply rails. r includes the on-resistance of the power-fets and r sns . the r dson of the high side fet should match that of the low side fet. l is a function of rotor position. each pulse will have a peak value v sensepeak of vr v r sensepeak sns motor t e on lr =- ? ? ? ? ? - 1 / where rrrr ll l l sdon sense ll = + () + = - - 075 2 075 . . what is important for sensing rotor position is the amplitude difference between each of the three pairs of current sense pulses. this can be seen by triggering on i sns on an oscilloscope with the rc vco pin shorted to ground. one should see the current waveform of figure 5. allowing the peak current sense pulse to reach an amplitude of 0.5v (by adjusting c sns , and hence t on ) or, allowing the difference between the maximum and minimum of the 6 pulses to be >50mv, should suffice for adequate rotor position sensing. a good starting value for t on is 200s, requiring c sns = 5.6nf. rinit the initial time interval between sample pulses during start-up is set by r init . this time interval (t init ) occurs while the rc vco pin is less than 0.25 volts. r t c init init vco = 343 . abcdefa 3.75v c vco 2.0v vco out figure 6. commutation timing and sequencing. direction outputs input samples state reverse n3 n2 n1 p3 p2 p1 forward n1 n2 n3 p1 p2 p3 forward reverse a off off on on off off ph2 ph2 b off off on off on off ph1 ph3 c on off off off on off ph3 ph1 d on off off off off on ph2 ph2 e off on off off off on ph1 ph3 f off on off on off off ph3 ph1 table 1. commutation states.
ML4428 rev. 1.0 11/17/2000 11 start-up sequencing when the motor is initially at rest, it is generating no back-emf. because a back-emf signal is required for closed loop commutation, the motor must be started by other means until a velocity sufficient to generate some back-emf is attained. start for rc vco voltages of less than 0.6v the ML4428 will send 6 sample pulses to the motor to determine the rotor position and drive the proper windings to produce desired rotation. this will result in motor acceleration until the rc vco pin achieves 0.6v and closed loop operation begins. this technique results in zero reverse rotation and minimizes start-up time. the sample time pulses are set by c sns and the initial sample interval is set by r init . this sense technique is not effective for air core motors, since a minimum of 30% inductance difference must occur when the motor moves. direction the direction of motor rotation is controlled by the commutation states as given in table 1. the state sequence is controlled by the f/ r . run when the rc vco pin exceeds 0.6v the device will enter run mode. at this time the motor speed should be about 8% frpm max and be high enough to generate a detectable bemf and allow closed loop operation to begin. the commutation position compensation has been previously discussed. the motor will continue to accelerate as long as the voltage on the rc vco is less than the voltage on v speed . during this time the motor will receive full n-channel drive limited only by i limit . as the voltage on rc vco approaches that of v speed the c isc capacitor will charge and begin to control the gate drive to the n-channel transistor by setting a level for comparison on the 25khz pwm saw tooth waveform generated on c pwm . the compensation of the speed loop is accomplished on c sc and on c isc which are outputs of transconductance amplifiers with a gm = 2.3 10 C4 . figure 8. speed control block diagram. + C + C mode select i sns rc vco v speed c sc c isc 8 20 1 c pwm 6 21 5 + C 0.23mmho 0.23mmho level shift +1.4v linear control to low-side gate drive pwm control to commutation logic figure 7. ilimit output off-time vs. cos. note: 100pf gives 10s, 200pf gives 20s, etc. 0 100 200 300 400 500 60 50 40 30 20 10 0 t off (s) c ios (pf) slope dt c dv i v a k == = m = 5 50 100 w speed control the speed control section of the ML4428 is detailed in figure 8. the two transconductance amplifiers with outputs at c sc and c isc each have a gm of 0.23mmhos. the bandwidth of the current feedback component of the speed control is set at c isc as follows: f cc db isc isc 3 45 23 10 2 366 10 = p = -- .. for f 3db = 50khz, c isc would be 730pf. the filter components on the c sc pin set the dominant pole in the system and should have a bandwidth of about 10% of the position filter on the rc vco pin. typically this is in the 1 to 10hz range. y
ML4428 12 rev. 1.0 11/17/2000 output drivers the p-channel drivers are emitter follower type with 5ma pull down currents. the n-channel drivers are totem pole with a 1200y resistor in series with the pull up device. crossover comparators are employed with each driver pair, eliminating the potential of crossover, and hence, shoot-through currents. braking when brake is pulled low all 3 p-channel drivers will be turned off and all 3 n-channel drivers will be turned on. power fail in the event of a power fail, i.e. v cc falls below 8.75v all 6 output drivers will be turned off. higher voltage motor drive the ML4428 can be used to drive higher voltage motors by means of level shifters to the high side drive transistors. this can be accomplished by using dedicated high side drivers for applications greater than 80v or a simple npn level shift as shown in figure 9 for applications below 80v. figure 10 shows how to interface to the ir2118, high side drivers from i.r. this allows driving motors up to 600v. the brake pin can be pulsed prior to startup with an rc circuit. this charges the bootstrap capacitors for three inexpensive high side drivers
ML4428 rev. 1.0 11/17/2000 13 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 i sns p1 p2 p3 csc c pwm v ref v speed n1 n2 n3 f/r vco v cc gnd r ref c ios brake phi3 phi2 phi1 c isc rc vco r init v flt c sns r vco c vco ML4428 0.1 m f 10k w 10 m f 2m w run pwr fail 1 m f 2k w res1 80k w res1 res1 brake 100pf 120k w motor 300pf 50k w 1k w 1nf 1 m f 0.1 m f 0.1 m f speed control voltage 20k w 100 w 100 w 100 w vco 1.5k w fwd/reverse +12v 0.1 m f 0.1 m f 2k w 2k w 2k w irfr120 irfr120 irfr120 irfr9120 irfr9120 irfr9120 q3 2n6718 1k w 0.1 m f +12v +24 to 60v 0.1 m f 330 m f q2 2n6718 q1 2n6718 5.6nf 750pf 2k w 2k w 2k w v motor figure 9. driving higher voltage motors: 24v to 80v.
ML4428 14 rev. 1.0 11/17/2000 figure 11. ML4428 high voltage motor driver: 12v to 500v 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 i sns p1 p2 p3 csc c pwm v ref v speed n1 n2 n3 f/r vco v cc gnd r ref c os brake phi3 phi2 phi1 c isc rc vco r init v flt c sns r vco c vco ML4428 750pf 10k w 2k w 80k w 1 m f 10 m f run brake pwr fail 5.11k w 5.11k w 5.11k w 0.01 m f 120k w motor 330pf 1k w 12k w 1nf 10 m f 0.1 m f v speed 787 w 10k w vco fwd/reverse +12v 25v 1 m f 0.1 m f 0.01 m f 100 w 100 w 100 w irf720 irf720 irf720 ph3 ph2 ph1 330 m f 400v irf720 irf720 irf720 v motor 25v 2.2 m f 100 w 1 2 3 4 8 7 6 5 v cc in com n/c vb ho vs n/c ir2118 mur150 +12v 25v 2.2 m f 25v 0.1 m f 25v 0.1 m f 25v 0.1 m f 100 w 1 2 3 4 8 7 6 5 v cc in com n/c vb ho vs n/c ir2118 mur150 25v 2.2 m f 100 w 1 2 3 4 8 7 6 5 v cc in com n/c vb ho vs n/c ir2118 mur150 r sense 300m w 10w 0.01 m f 5.6nf 2m w note: refer to ik2118 data sheet for complete information on using this part with different fets and igbts.
ML4428 rev. 1.0 11/17/2000 15 physical dimensions inches (millimeters) package: p28n 28-pin narrow pdip seating plane 0.280 - 0.296 (7.11 - 7.52) pin 1 id 0.299 - 0.325 (7.60 - 8.26) 1.355 - 1.365 (34.42 - 34.67) 0.015 - 0.021 (0.38 - 0.53) 0.100 bsc (2.54 bsc) 0.008 - 0.012 (0.20 - 0.31) 0.020 min (0.51 min) 28 0o - 15o 1 0.045 - 0.055 (1.14 - 1.40) 0.180 max (4.57 max) 0.125 - 0.135 (3.18 - 3.43)
ML4428 16 rev. 1.0 11/17/2000 ordering information part number temperature range package ML4428cp (eol) 0c to 70c 28-pin dip (p28n) ML4428cs (eol) 0c to 70c 28-pin soic (s28) ML4428ip C40c to 85c 28-pin dip (p28n) ML4428is C40c to 85c 28-pin soic (s28) physical dimensions inches (millimeters) seating plane 0.291 - 0.301 (7.39 - 7.65) pin 1 id 0.398 - 0.412 (10.11 - 10.47) 0.699 - 0.713 (17.75 - 18.11) 0.012 - 0.020 (0.30 - 0.51) 0.050 bsc (1.27 bsc) 0.022 - 0.042 (0.56 - 1.07) 0.095 - 0.107 (2.41 - 2.72) 0.005 - 0.013 (0.13 - 0.33) 0.090 - 0.094 (2.28 - 2.39) 28 0.009 - 0.013 (0.22 - 0.33) 0o - 8o 1 0.024 - 0.034 (0.61 - 0.86) (4 places) package: s28 28-pin soic life support policy fairchild? 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 life, 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 any component of a life support device or system whose failure 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 ?2000 fairchild semiconductor corporation disclaimer fairchild semiconductor reserves the right to make changes without further notice to any products herein to improve reliability, function or design. fairchild does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights, nor the rights of others.

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