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dw suffix plastic package case 751g (so16l) p suffix plastic package case 648 pin connections 16 1 16 1 11 5 2 1 error amp noninverting input current limit/ shutdown ground output a power ground v c output b v cc v ref 9 10 12 13 14 15 16 8 7 6 4 3 (top view) softstart ramp c t r t clock error amp output error amp inverting input device operating temperature range package ordering information mc33025dw MC34025p t a = 0 to +70 c so16l plastic dip t a = 40 to +105 c mc33025p plastic dip MC34025dw so16l order this document by MC34025/d 1 motorola analog ic device data
the MC34025 series are high speed, fixed frequency, doubleended pulse width modulator controllers optimized for high frequency operation. they are specifically designed for offline and dctodc converter applications offering the designer a cost effective solution with minimal external components. these integrated circuits feature an oscillator, a temperature compensated reference, a wide bandwidth error amplifier, a high speed current sensing comparator, steering flipflop, and dual high current totem pole outputs ideally suited for driving power mosfets. also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cyclebycycle current limiting, and a latch for single pulse metering. the flexibility of this series allows it to be easily configured for either current mode or voltage mode control. ? 50 ns propagation delay to outputs ? dual high current totem pole outputs ? wide bandwidth error amplifier ? fullylatched logic with double pulse suppression ? latching pwm for cyclebycycle current limiting ? softstart control with latched overcurrent reset ? input undervoltage lockout with hysteresis ? low startup current (500 m a typ) ? internally trimmed reference with undervoltage lockout ? 90% maximum duty cycle (externally adjustable) ? precision trimmed oscillator ? voltage or current mode operation to 1.0 mhz ? functionally similar to the uc3825 simplified application error amp oscillator 4 16 v ref clock 5 6 r t c t 3 7 ramp error amp output 2 inverting input 1 8 softstart softstar t latching pwm and steering flip flop ground 10 9 current limit/ shutdown output b 14 v c 13 v cc 15 uvlo 5.1v reference 11 noninverting input power ground 12 output a this device contains 227 active transistors. ? motorola, inc. 1996 rev 1
MC34025 mc33025 2 motorola analog ic device data maximum ratings rating symbol value unit power supply voltage v cc 30 v output driver supply voltage v c 20 v output current, source or sink (note 1) dc pulsed (0.5 m s) i o 0.5 2.0 a current sense, softstart, ramp, and error amp inputs v in 0.3 to +7.0 v error amp output and softstart sink current i o 10 ma clock and r t output current i co 5.0 ma power dissipation and thermal characteristics so16 package (case 751g) maximum power dissipation @ t a = + 25 c thermal resistance, junctiontoair dip package (case 648) maximum power dissipation @ t a = + 25 c thermal resistance, junctiontoair p d r q ja p d r q ja 862 145 1.25 100 mw c/w w c/w operating junction temperature t j +150 c operating ambient temperature (note 2) MC34025 mc33025 t a 0 to +70 40 to +105 c storage temperature range t stg 55 to +150 c electrical characteristics (v cc = 15 v, r t = 3.65 k w , c t = 1.0 nf, for typical values t a = + 25 c, for min/max values t a is the operating ambient temperature range that applies [note 2], unless otherwise noted.) characteristic symbol min typ max unit reference section reference output voltage (i o = 1.0 ma, t j = + 25 c) v ref 5.05 5.1 5.15 v line regulation (v cc = 10 v to 30 v) reg line 2.0 15 mv load regulation (i o = 1.0 ma to 10 ma) reg load 2.0 15 mv temperature stability t s 0.2 mv/ c total output variation over line, load, and temperature v ref 4.95 5.25 v output noise voltage (f = 10 hz to 10 khz, t j = + 25 c) v n 50 m v long term stability (t a = +125 c for 1000 hours) s 5.0 mv output short circuit current i sc 30 65 100 ma oscillator section frequency t j = + 25 c line (v cc = 10 v to 30 v) and temperature (t a = t low to t high ) f osc 380 370 400 400 420 430 khz frequency change with voltage (v cc = 10 v to 30 v) d f osc / d v 0.2 1.0 % frequency change with temperature (t a = t low to t high ) d f osc / d t 2.0 % sawtooth peak voltage v p 2.6 2.8 3.0 v sawtooth valley voltage v v 0.7 1.0 1.25 v clock output voltage high state low state v oh v ol 3.9 4.5 2.3 2.9 v notes: 1. maximum package power dissipation limits must be observed. 2. low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. t low = 0 c for MC34025 t high = +70 c for MC34025 t low = 40 c for mc33025 t high = +105 c for mc33025
MC34025 mc33025 3 motorola analog ic device data electrical characteristics (v cc = 15 v, r t = 3.65 k w , c t = 1.0 nf, for typical values t a = + 25 c, for min/max values t a is the operating ambient temperature range that applies [note 2], unless otherwise noted.) characteristic symbol min typ max unit error amplifier section input offset voltage v io 15 mv input bias current i ib 0.6 3.0 m a input offset current i io 0.1 1.0 m a openloop voltage gain (v o = 1.0 v to 4.0 v) a vol 60 95 db gain bandwidth product (t j = + 25 c) gbw 4.0 8.3 mhz common mode rejection ratio (v cm = 1.5 v to 5.5 v) cmrr 75 95 db power supply rejection ratio (v cc = 10 v to 30 v) psrr 85 110 db output current, source (v o = 4.0 v) output current, sink (v o = 1.0 v) i source i sink 0.5 1.0 3.0 3.6 ma output voltage swing, high state (i o = 0.5 ma) output voltage swing, low state (i o = 1.0 ma) v oh v ol 4.5 0 4.75 0.4 5.0 1.0 v slew rate sr 6.0 12 v/ m s pwm comparator section ramp input bias current i ib 0.5 5.0 m a duty cycle, maximum duty cycle, minimum dc (max) dc (min) 80 90 0 % zero duty cycle threshold voltage pin 3(4) (pin 7(9) = 0 v) v th 1.1 1.25 1.4 v propagation delay (ramp input to output, t j = + 25 c) t plh(in/out) 60 100 ns siftstart section charge current (v softstart = 0.5 v) i chg 3.0 9.0 20 m a discharge current (v softstart = 1.5 v) i dischg 1.0 4.0 ma current sense section input bias current (pin 9(12) = 0 v to 4.0 v) i ib 15 m a current limit comparator threshold sh td c t th h ld v th v 0.9 125 1.0 140 1.10 155 v p shutdown comparator threshold th v th 1.25 1.40 1.55 propagation delay (current limit/shutdown to output, t j = + 25 c) t plh(in/out) 50 80 ns output section output voltage low state (i sink = 20 ma) (i sink = 200 ma) high state (i source = 20 ma) (i source = 200 ma) v ol v oh 13 12 0.25 1.2 13.5 13 0.4 2.2 v output voltage with uvlo activated (v cc = 6.0 v, i sink = 0.5 ma) v ol(uvlo) 0.25 1.0 v output leakage current (v c = 20 v) i l 100 500 m a output voltage rise time (c l = 1.0 nf, t j = + 25 c) t r 30 60 ns output voltage fall time (c l = 1.0 nf, t j = + 25 c) t f 30 60 ns undervoltage lockout section startup threshold (v cc increasing) v th(on) 8.8 9.2 9.6 v uvlo hysteresis voltage (v cc decreasing after turnon) v h 0.4 0.8 1.2 v total device power supply current startup (v cc = 8.0 v) operating i cc 0.5 25 1.2 35 ma notes: 1. maximum package power dissipation limits must be observed. 2. low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. t low = 0 c for MC34025 t high = +70 c for MC34025 t low = 40 c for mc33025 t high = +105 c for mc33025
MC34025 mc33025 4 motorola analog ic device data gain phase 1 c t = 1. 100 nf 2. 47 nf 3. 22 nf 4. 10 nf 5. 4.7 nf 6. 2.2 nf 7. 1.0 nf 8. 470 pf 9. 220 pf 2 3 4 5 6 7 8 9 55 25 0 25 75 100 125 a vol , open loop voltage gain (db) , oscillator frequency (khz) f osc figure 1. timing resistor versus oscillator frequency , timing resistor ( ) 100 1000 10 4 10 5 10 6 10 7 f osc , oscillator frequency (hz) figure 2. oscillator frequency versus temperature t a , ambient temperature ( c) figure 3. error amp open loop gain and phase versus frequency 10 100 1.0 k 10 k 100 k 1.0 m 10 m f, frequency (hz) figure 4. pwm comparator zero duty cycle threshold voltage versus temperature 55 25 0 25 50 75 100 t a , ambient temperature ( c) figure 5. error amp small signal transient response figure 6. error amp large signal transient response r t w 125 0 45 90 135 , excess phase ( c) q v th , zero duty cycle (v) 0.1 m s/div 0.1 m s/div v cc = 15 v r t = 3.6 k c t = 1.0 nf r t = 1.2 k c t = 1.0 nf r t = 36 k c t = 1.0 nf 50 50 khz 400 khz 1.0 mhz v cc = 15 v pin 7(9) = 0 v v cc = 15 v t a = + 25 c 1.3 1.28 1.26 1.24 1.22 1.2 100 k 10 k 1.0 k 470 1200 1000 800 600 400 200 120 100 80 60 40 20 0 0 20 2.55 v 2.5 v 2.45 v 3.0 v 2.5 v 2.0 v
MC34025 mc33025 5 motorola analog ic device data (cl), current limit threshold change (mv) v th , shutdown threshold voltage (v) v th v cc = 15 v 0 10 20 30 40 50 t a , ambient temperature ( c) , reference short circuit current (ma) figure 7. reference voltage change versus source current , reference voltage change (mv) i source , source current (ma) figure 8. reference short circuit current versus temperature 55 t a , ambient temperature ( c) 25 0 25 50 75 100 125 figure 9. reference line regulation figure 10. reference load regulation figure 11. current limit comparator threshold change versus temperature t a , ambient temperature ( c) figure 12. shutdown comparator threshold voltage versus temperature 55 25 25 50 75 100 125 50 25 0 25 50 75 125 v ref i sc 100 0 t a = + 25 c t a = 55 c v ref line regulation 10 v 24 v 2.0 ms/div 2.0 mv/div v ref line regulation 1.0 ma 10 ma 2.0 ms/div 2.0 mv/div t a = +125 c d v cc = 15 v v cc = 15 v 1.42 4.0 2.0 4.0 8.0 10 12 0 5.0 10 15 20 25 30 66 65.6 65.2 64.8 64.4 64 1.50 1.46 1.38 1.34 1.30 0 2.0 6.0
MC34025 mc33025 6 motorola analog ic device data source saturation (load to ground) v cc = 15 v 80 m s pulsed load 120 hz rate t a = + 25 c v cc ground sink saturation (load to v cc ) v cc decreasing v cc increasing v cc = 15 v t a , ambient temperature ( c) , output saturation voltage (v) figure 13. softstart charge current versus temperature a) 55 25 0 25 50 75 100 125 i o , output load current (a) figure 14. output saturation voltage versus load current 0 0.2 0.4 0.6 0.8 1.0 figure 15. drive output rise and fall time figure 16. drive output rise and fall time v cc , supply voltage (v) 0 4.0 8.0 12 16 20 , supply current (ma) m i chg , soft-start charge current ( v sat i cc figure 17. supply voltage versus supply current output rise & fall time 1.0 nf load 50 ns/div output rise & fall time 10.0 nf load 50 ns/div r t = 3.65 k w c t = 1.0 nf 0 2.0 1.0 10 9.5 9.0 8.5 8.0 7.5 7.0 1.0 2.0 0 30 25 20 15 10 5.0 0
MC34025 mc33025 7 motorola analog ic device data v ref v cc uvlo reference regulator 4.2 v figure 18. representative block diagram q s r q q t steering flip flop output a 1.0 v 0.5 v 16 4 5 6 7 3 2 1 8 c ss 10 9 11 12 14 13 15 pwm latch softstart latch v in 9.0 m a error amp pwm comparator v ref uvlo 9.2 v oscillator 1.4 v current limit q s r v cc clock r t c t noninverting input inverting input error amp output ramp softstart ground current limit/ shutdown power ground output b v c v cc + 1.25 v shutdown figure 19. current limit operating waveforms output b output a pwm comparator ramp clock c t softstart error amp output
MC34025 mc33025 8 motorola analog ic device data operating description the mc33025 and MC34025 series are high speed, fixed frequency, doubleended pulse width modulator controllers optimized for high frequency operation. they are specifically designed for offline and dctodc converter applications offering the designer a cost effective solution with minimal external components. a representative block diagram is shown in figure 18. oscillator the oscillator frequency is programmed by the values selected for the timing components r t and c t . the r t pin is set to a temperature compensated 3.0 v. by selecting the value of r t , the charge current is set through a current mirror for the timing capacitor c t . this charge current runs continuously through c t . the discharge current is ratioed to be 10 times the charge current, which yields the maximum duty cycle of 90%. c t is charged to 2.8 v and discharged to 1.0 v. during the discharge of c t , the oscillator generates an internal blanking pulse that resets the pwm latch, inhibits the outputs, and toggles the steering flipflop. the threshold voltages on the oscillator comparator is trimmed to guarantee an oscillator accuracy of 5.0% at 25 c. additional dead time can be added by externally increasing the charge current to c t as shown in figure 23. this changes the charge to discharge ratio of c t which is set internally to i charge /10 i charge . the new charge to discharge ratio will be: % deadtime i additiona l i charge 10 (i charge ) a bidirectional clock pin is provided for synchronization or for master/slave operation. as a master, the clock pin provides a positive output pulse during the discharge of c t . as a slave, the clock pin is an input that resets the pwm latch and blanks the drive output, but does not discharge c t . therefore, the oscillator is not synchronized by driving the clock pin alone. figures 29 and 30 provide suggested synchronization. error amplifier a fully compensated error amplifier is provided. it features a typical dc voltage gain of 95 db and a gain bandwidth product of 8.3 mhz with 75 degrees of phase margin (figure 3). typical application circuits will have the noninverting input tied to the reference. the inverting input will typically be connected to a feedback voltage generated from the output of the switching power supply. both inputs have a common mode voltage (v cm ) input range of 1.5 v to 5.5 v. the error amplifier output is provided for external loop compensation. softstart latch softstart is accomplished in conjunction with an external capacitor. the soft start capacitor is charged by an internal 9.0 m a current source. this capacitor clamps the output of the error amplifier to less than its normal output voltage, thus limiting the duty cycle. the time it takes for a capacitor to reach full charge is given by: t (4.5 ? 10 5 )c soft-start a softstart latch is incorporated to prevent erratic operation of this circuitry. two conditions can cause the softstart circuit to latch so that the softstart capacitor stays discharged. the first condition is activation of an undervoltage lockout of either v cc or v ref . the second condition is when current sense input exceeds 1.4 v. since this latch is aset dominanto, it cannot be reset until either of these signals is removed, and the voltage at c softstart is less than 0.5 v. pwm comparator and latch a pwm circuit typically compares an error voltage with a ramp signal. the outcome of this comparison determines the state of the output. in voltage mode operation the ramp signal is the voltage ramp of the timing capacitor. in current mode operation the ramp signal is the voltage ramp induced in a current sensing element. the ramp input of the pwm comparator is pinned out so that the user can decide which mode of operation best suits the application requirements. the ramp input has a 1.25 v offset such that whenever the voltage at this pin exceeds the error amplifier output voltage minus 1.25 v, the pwm comparator will cause the pwm latch to set, disabling the outputs. once the pwm latch is set, only a blanking pulse by the oscillator can reset it, thus initiating the next cycle. a toggle flip flop connected to the output of the pwm latch controls which output is active. the flip flop is pulsed by an or gate that gets its inputs from the oscillator clock and the output of the pwm latch. a pulse from either one will cause the flip flop to enable the other output. current limiting and shutdown a pin is provided to perform current limiting and shutdown operations. two comparators are connected to the input of this pin. when the voltage at this pin exceeds 1.0 v, one of the comparators is activated. the output of this comparator sets the pwm latch, which disables the output. in this way cyclebycycle current limiting is accomplished. if a current limit resistor is used in series with the power devices, the value of the resistor is found by: r sense 1.0 v i pk (switch) if the voltage at this pin exceeds 1.4 v, the second comparator is activated. this comparator sets a latch which, in turn, causes the softstart capacitor to be discharged. in this way a ahiccupo mode of recovery is possible in the case of output short circuits. if a current limit resistor is used in series with the output devices, the peak current at which the controller will enter a ahiccupo mode is given by: i shutdown 1.4 v r sense
MC34025 mc33025 9 motorola analog ic device data undervoltage lockout there are two undervoltage lockout circuits within the ic. the first senses v cc and the second v ref . during powerup, v cc must exceed 9.2 v and v ref must exceed 4.2 v before the outputs can be enabled and the softstart latch released. if v cc falls below 8.4 v or v ref falls below 3.6 v, the outputs are disabled and the softstart latch is activated. when the uvlo is active, the part is in a low current standby mode allowing the ic to have an offline bootstrap startup circuit. typical startup current is 500 m a. output the MC34025 has two high current totem pole outputs specifically designed for direct drive of power mosfets. they are capable of up to 2.0 a peak drive current with a typical rise and fall time of 30 ns driving a 1.0 nf load. separate pins for v c and power ground are provided. with proper implementation, a significant reduction of switching transient noise imposed on the control circuitry is possible. the separate v c supply input also allows the designer added flexibility in tailoring the drive voltage independent of v cc . reference a 5.1 v bandgap reference is pinned out and is trimmed to an initial accuracy of 1.0% at 25 c. this reference has short circuit protection and can source in excess of 10 ma for powering additional control system circuitry. design considerations do not attempt to construct the converter on wirewrap or plugin prototype boards. with high frequency, high power, switching power supplies it is imperative to have separate current loops for the signal paths and for the power paths. the printed circuit layout should contain a ground plane with low current signal and high current switch and output grounds returning on separate paths back to the input filter capacitor. all bypass capacitors and snubbers should be connected as close as possible to the specific part in question. the pc board lead lengths must be less than 0.5 inches for effective bypassing or snubbing. instabilities in current mode control, an instability can be encountered at any given duty cycle. the instability is caused by the current feedback loop. it has been shown that the instability is caused by a double pole at half the switching frequency. if an external ramp (s e ) is added to the ontime ramp (s n ) of the currentsense waveform, stability can be achieved (see figure 20). one must be careful not to add too much ramp compensation. if too much is added, the system will start to perform like a voltage mode regulator. all benefits of current mode control will be lost. figures 28a and 28b show examples of two different ways in which external ramp compensation can be implemented. 1.25 v + + ramp input current signal s n ramp compensation s e figure 20. ramp compensation a simple equation can be used to calculate the amount of external ramp necessary to add that will achieve stability in the current loop. for the following equations, the calculated values for the application circuit in figure 36 are also shown. s e v o l n s n p (r s ) a i where: = dc output voltage = number of power transformer primary = or secondary turns = gain of the current sense network = (see figures 25, 26 and 27) = output inductor = current sense resistance v o n p , n s a i l r s 0.115 v m s for the application circuit: s e 5 1.8 m 4 16 ( 0.3 )( 0.55 )
MC34025 mc33025 10 motorola analog ic device data pin function description pin no. fi dii dip/soic function description 1 error amp inverting input this pin is usually used for feedback from the output of the power supply. 2 error amp noninverting input this pin is used to provide a reference in which an error signal can be produced on the output of the error amp. usually this is connected to v ref , however an external reference can also be used. 3 error amp output this pin is provided for compensating the error amp for poles and zeros encountered in the power supply system, mostly the output lc filter. 4 clock this is a bidirectional pin used for synchronization. 5 r t the value of r t sets the charge current through timing capacitor, c t . 6 c t in conjunction with r t , the timing capacitor sets the switching frequency. because this part is a pushpull output, each output runs at onehalf the frequency set at this pin. 7 ramp input for voltage mode operation this pin is connected to c t . for current mode operation this pin is connected through a filter to the current sensing element. 8 softstart a capacitor at this pin sets the softstart time. 9 current limit/shutdown this pin has two functions. first, it provides cyclebycycle current limiting. second, if the current is excessive, this pin will reinitiate a softstart cycle. 10 ground this pin is the ground for the control circuitry. 11 output a this is a high current totem pole output. 12 power ground this is a separate power ground return that is connected back to the power source. it is used to reduce the effects of switching transient noise on the control circuitry. 13 v c this is a separate power source connection for the outputs that is connected back to the power source input. with a separate power source connection, it can reduce the effects of switching transient noise on the control circuitry. 14 output b this is a high current totem pole output. 15 v cc this pin is the positive supply of the control ic. 16 v ref this is a 5.1 v reference. it is usually connected to the noninverting input of the error amplifier. output voltage feedback input 2 1 3 7 6 5 4 1.25 v oscillator v ref c t figure 21. voltage mode operation in voltage mode operation, the control range on the output of the error amplifier from 0% to 90% duty cycle is from 2.25 v to 4.05 v. output voltage feedback input 2 1 3 7 6 5 4 1.25 v oscillator v ref c t from current sense element figure 22. current mode operation in current mode control, an rc filter should be placed at the ramp input to filter the leading edge spike caused by turnon of a power mosfet.
MC34025 mc33025 11 motorola analog ic device data c t v ref r dt r t 4 oscillator figure 23. dead time addition 5 6 additional dead time can be added by the addition of a dead time resistor from v ref to c t . see text on oscillator section for more information. 5.0 v 0 v c t r t oscillator figure 24. external clock synchronization 4 5 6 the sync pulse fed into the clock pin must be at least 3.9 v. r t and c t need to be set 10% slower than the sync frequency. this circuit is also used in voltage mode operation for master/slave operation. the clock signal would be coming from the master which is set at the desired operating frequency, while the slave is set 10% slower. figure 25. resistive current sensing i sense 9 the addition of an rc filter will eliminate instability caused by the leading edge spike on the current waveform. this sense signal can also be used at the ramp input pin for current mode control. for ramp compensation it is necessary to know the gain of the current feedback loop. if a transformer is used, the gain can be calculated by: a i r sense turns ratio figure 26. primary side current sensing r w i sense 9 figure 27. primary or secondary side current sensing 0 i sense r w 9 a i r w turns ratio the addition of an rc filter will eliminate instability caused by the leading edge spike on the current waveform. this sense signal can also be used at the ramp input pin for current mode control. for ramp compensation it is necessary to know the gain of the current feedback loop. the gain can be calculated by:
MC34025 mc33025 12 motorola analog ic device data 3 7 6 5 4 figure 28a. slope compensation (noise sensitive) oscillator c t c 1 r 1 r 2 current sense information 1.25 v this method of slope compensation is easy to implement, however, it is noise sensitive. capacitor c 1 provides ac coupling. the oscillator signal is added to the current signal by a voltage divider consisting of resistors r 1 and r 2 . 7 3 7 3 figure 28b. slope compensation (noise immune) r w output r m c m r f c f 1.25 v ramp input current sense transformer current sense resistor r f c f c m 1.25 v r m ramp input output figure 28. keeps fig numbering sequence correct when only one output is used, this method of slope compensation can be used and it is relatively noise immune. resistor r m and capacitor c m provide the added slope necessary. by choosing r m and c m with a larger time constant than the switching frequency, you can assume that its charge is linear. first choose c m , then r m can be adjusted to achieve the required slope. the diode provides a reset pulse at the ramp input at the end of every cycle. the charge current i m can be calculated by i m = c m s e . then r m can be calculated by r m = v cc /i m . figure 29. current mode master/slave operation over short distances v ref 6 5 4 oscillator c t r t 6 5 4 oscillator
MC34025 mc33025 13 motorola analog ic device data figure 30. synchronization over long distances mc34071 1.0 k 3320 provides current sense amplification & eliminates leading edge spike provides leading edge blanking mmbt3904 1.0 k from curr sense from curr sense 100 k 562 680 pf 680 pf 562 output b output a 79 10 8 12 14 11 4 16 13 15 6 5 1 3 2 100 mmbt3904 mmbd914 470 pf 22 k 21 470 pf 30 k +15 v 1.0 k 2200 430 mmbt3906 4700 20 4.7 k 4.7 k 10 k 10 k +15 v 4 16 13 15 2 79 10 8 14 11 6 5 1 3 output a output b 3.0 k MC34025 MC34025 fb fb synchronizes both converters to the same operating frequency synchronizes both converters to the same phase 12
MC34025 mc33025 14 motorola analog ic device data v ref r 2 r 1 c ss 1 2 8 + figure 31. buffered maximum clamp level in voltage mode operation, the maximum duty cycle can be clamped. by the addition of a pnp transistor to buffer the clamp voltage, the softstart current is not affected by r 1 . the new equation for softstart is t v clamp 0.6 9.0 m a c ss in current mode operation, this circuit will limit the maximum voltage allowed at the ramp input to end a cycle. q q t v in to current sense input r s 12 11 14 15 v c base charge removal 0 + i b figure 32. bipolar transistor drive the totem pole output can furnish negative base current for enhanced transistor turnoff, with the addition of the capacitor in series with the base. q q t 12 11 14 15 v c isolation boundary figure 33. isolated mosfet drive 12 11 14 15 q q t v c v c figure 34. direct transformer drive the totem pole output can easily drive pulse transformers. a schottky diode is recommended when driving inductive loads at high frequencies. the diode can reduce the driver's power dissipation due to excessive ringing, by preventing the output pin from being driven below ground. q q t v in to current sense input r s 12 11 14 15 v c figure 35. mosfet parasitic oscillations a series gate resistor may be needed to damp high frequency parasitic oscillation caused by a mosfet's input capacitance and any series wiring inductance in the gatesource circuit. the series resistor will also decrease the mosfet's switching speed. a schottky diode can reduce the driver's power dissipation due to excessive ringing, by preventing the output pin from being driven below ground. the schottky diode also prevents substrate injection when the output pin is driven below ground.
MC34025 mc33025 15 motorola analog ic device data figure 36. application circuit figure 36. keeps fig numbering sequence correct primary: 16 turns center tapped #48 awg (1300 strands litz wire) secondary: 4 turns center tapped 0.003o (2 layers) copper foil bootstrap: 1 turn added to each secondary output #36 awg core: philips 3f3, part #4312 020 4124 bobbin: philips part #4322 021 3525 coilcraft p3269a 2 turns #48 awg (1300 strands litz wire) core: philips 3f3, part #ep103f3 bobbin: philips part #ep10pcb18 l = 1.8 h coilcraft p3270a power fet: aavid heatsink #533902b02554 with clip all power devices are insulated with berquist silpad 1500 5 (1.5 ) resistors in parallel t 1 l 1 1 2 heatsinks output rectifiers: aavid heatsink #533402b02552 with clip insulators test condition result line regulation load regulation output ripple efficiency v = 40 v to 56 v, i = 15 a in o v = 48 v, i = 8.0 v to 15 a in o v = 48 v, i = 15 a in o v = 48 v, i = 15 a in o m w m 14 mv = 0.275% 54 mv = 1.0% 50 mvpp 71.2% 7 turns #18 awg, 1/2o diameter air core coilcraft p3271a l 2 2 (1.0 f) cearmic capacitors in parallel 3 m 10 (1.0 f) ceramic capacitors in parallel v in 100 47 k 47 4.7 1n5819 1500 pf 22 5.0 v t 1 22 1500 pf 1n5819 l 2 15 13 14 11 12 9 16 4 5 6 7 3 2 1 8 2.0 k 1000 pf 1.2 k 1.0 0.01 22 k 0.015 f m 47 k 0.01 error amp 1.25 v oscillator 4.0 v 9.0 a m r s q 10 shutdown 1.4 v current limit 9.2 v 100 47 1n5819 4.7 4.7 1n5819 10 10 100 220 pf r s q 0.5 v reference regulator 1.0 v pwm latch mbr2535ctl w 0.3 l 1 2.0 f m 10 f m irf640 50 1600 pf 1.8 h m 900 nh 36 v to 56 v v o 3 2 1 q q t
MC34025 mc33025 16 motorola analog ic device data 4.0 6.5 (top view) figure 37. pc board with components 100 pf 1 + 10 + 1000 pf 0.01 0.01 2200 pf 1n5819 1n5819 1n5819 1n5819 mbr 2535cti 1500 pf mbr 2535cti 1500 pf 1 1 4.7 h m 100 pf
MC34025 mc33025 17 motorola analog ic device data (top view) figure 38. pc board without components 4.0 6.5 (bottom view)
MC34025 mc33025 18 motorola analog ic device data 0.050 bsc min max millimeters 10.15 7.40 2.35 0.35 0.50 0.25 0.10 0 10.05 0.25 10.45 7.60 2.65 0.49 0.90 0.32 0.25 7 10.55 0.75 1.27 bsc p suffix plastic package case 64808 outline dimensions dw suffix plastic package case 751g02 (so16l) min min max max inches millimeters dim a b c d f g h j k l m s 18.80 6.35 3.69 0.39 1.02 0.21 2.80 7.50 0 0.51 19.55 6.85 4.44 0.53 1.77 0.38 3.30 7.74 10 1.01 0.740 0.250 0.145 0.015 0.040 0.008 0.110 0.295 0 0.020 0.770 0.270 0.175 0.021 0.070 0.015 0.130 0.305 10 0.040 notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: inch. 3. dimension l to center of leads when formed parallel. 4. dimension b does not include mold flash. 5. rounded corners optional. 2.54 bsc 1.27 bsc 0.100 bsc 0.050 bsc a b 18 9 16 f h g d 16 pl s c t seating plane k j m l ta 0.25 (0.010) m m 18 9 16 min max max inches dim a b c d f g j k m p r 0.400 0.292 0.093 0.014 0.020 0.010 0.004 0 0.395 0.010 0.411 0.299 0.104 0.019 0.035 0.012 0.009 7 0.415 0.029 a b p 8 pl g 14 pl t d 16 pl k c seating plane m r x 45 0.25 (0.010) b m m 0.25 (0.010) t a b m s s notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. dimensions a and b do not include mold protrusion. 4. maximum mold protrusion 0.15 (0.006) per side. 5. dimension d does not include dambar protrusion. allowable dambar protrusion shall be 0.13 (0.005) total in excess of d dimension at maximum material condition. f j
MC34025 mc33025 19 motorola analog ic device data t fn suffix plastic package case 77502 (plcc) outline dimensions a b c e f g h j k r u v w x y z g1 k1 min min max max inches millimeters dim 9.78 9.78 4.20 2.29 0.33 0.66 0.51 0.64 8.89 8.89 1.07 1.07 1.07 e 2 7.88 1.02 10.03 10.03 4.57 2.79 0.48 0.81 e e 9.04 9.04 1.21 1.21 1.42 0.50 10 8.38 e 0.385 0.385 0.165 0.090 0.013 0.026 0.020 0.025 0.350 0.350 0.042 0.042 0.042 e 2 0.310 0.040 0.395 0.395 0.180 0.110 0.019 0.032 e e 0.356 0.356 0.048 0.048 0.056 0.020 10 0.330 e 1.27 bsc 0.050 bsc notes: 1. datums l, m, and n determined where top of lead shoulder exits plastic body at mold parting line. 2. dim g1, true position to be measured at datum t, seating plane. 3. dim r and u do not include mold flash. allowable mold flash is 0.010 (0.250) per side. 4. dimensioning and tolerancing per ansi y14.5m, 1982. 5. controlling dimension: inch. 6. the package top may be smaller than the package bottom by up to 0.012 (0.300). dimensions r and u are determined at the outermost extremes of the plastic body exclusive of mold flash, tie bar burrs, gate burrs and interlead flash, but including any mismatch between the top and bottom of the plastic body. 7. dimension h does not include dambar protrusion or intrusion. the dambar protrusion(s) shall not cause the h dimension to be greater than 0.037 (0.940). the dambar intrusion(s) shall not cause the h dimension to be smaller than 0.025 (0.635). n y brk m l w v d d 20 1 a r z c g g1 e j view s b u z g1 x h f view s k k1 view dd 0.007 (0.180) t l m s n s m 0.007 (0.180) t l m s n s m seating plane 0.010 (0.250) t l m s n s s 0.007 (0.180) t l m s n s m 0.007 (0.180) t l m s n s m 0.010 (0.250) t l m s n s s 0.007 (0.180) t l m s n s m 0.007 (0.180) t l m s n s m 0.004 (0.100)
MC34025 mc33025 20 motorola analog ic device data motorola reserves the right to make changes without further notice to any products herein. motorola makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. atypicalo parameters which may be provided in motorola data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including atypicalso must be validated for each customer application by customer's technical experts. motorola does not convey any license under its patent rights nor the rights of others. motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the motorola product could create a situation where personal injury or death may occur. should buyer purchase or use motorola products for any such unintended or unauthorized application, buyer shall indemnify and hold motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that motorola was negligent regarding the design or manufacture of the part. motorola and are registered trademarks of motorola, inc. motorola, inc. is an equal opportunity/affirmative action employer. mfax is a trademark of motorola, inc. how to reach us: usa / europe / locations not listed : motorola literature distribution; japan : nippon motorola ltd.: spd, strategic planning office, 4321, p.o. box 5405, denver, colorado 80217. 3036752140 or 18004412447 nishigotanda, shinagawaku, tokyo 141, japan. 81354878488 mfax ? : rmfax0@email.sps.mot.com touchtone 6 022446609 asia / pacific : motorola semiconductors h.k. ltd.; 8b tai ping industrial park, us & canada only 18007741848 51 ting kok road, tai po, n.t., hong kong. 85226629298 internet : http://motorola.com/sps MC34025/d ?

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