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november 2003 1/15 viper12adip viper12as low power off line smps primary switcher ? typical power capability n fixed 60 khz switching frequency n 9v to 38v wide range v dd voltage n current mode control n auxiliary undervoltage lockout with hysteresis n high voltage start up current source n overtemperature, overcurrent and overvoltage protection with autorestart description the viper12a combines a dedicated current mode pwm controller with a high voltage power mosfet on the same silicon chip. typical applications cover off line power supplies for battery charger adapters, standby power supplies for tv or monitors, auxiliary supplies for motor control, etc. the internal control circuit offers the following benefits: C large input voltage range on the v dd pin accommodates changes in auxiliary supply voltage. this feature is well adapted to battery charger adapter configurations. C automatic burst mode in low load condition. C overvoltage protection in hiccup mode. mains type so-8 dip8 european (195 - 265 vac) 8 w 13 w us / wide range (85 - 265 vac) 5 w 8 w order codes package tube t&r so-8 viper12as viper12as 13tr dip-8 viper12adip so-8 dip-8 block diagram on/off 0.23 v drain source vdd pwm latch 60khz oscillator blanking + _ 8/14.5v _ + ff s r1 r4 q r3 fb regulator internal supply overvoltage latch overtemp. detector 1 k w 42v _ + r2 ff s r q 230 w
viper12adip / viper12as 2/15 pin function current and voltage conventions connection diagram name function v dd power supply of the control circuits. also provides a charging current during start up thanks to a high voltage current source connected to the drain. for this purpose, an hysteresis comparator monitors the v dd voltage and provides two thresholds: - v ddon : voltage value (typically 14.5v) at which the device starts switching and turns off the start up current source. - v ddoff : voltage value (typically 8v) at which the device stops switching and turns on the start up current source. source power mosfet source and circuit ground reference. drain power mosfet drain. also used by the internal high voltage current source during start up phase for charging the external v dd capacitor. fb feedback input. the useful voltage range extends from 0v to 1v, and defines the peak drain mosfet current. the current limitation, which corresponds to the maximum drain current, is obtained for a fb pin shorted to the source pin. i dd i d i fb v dd v fb v d fb vdd drain source control viper12a 1 2 3 4 drain drain drain drain 8 7 6 5 drain drain drain drain 1 2 3 4 8 7 6 5 fb vdd source fb vdd source source source so-8 dip8
viper12adip / viper12as 3/15 absolute maximum ratings note: 1. this parameter applies when the start up current source is off. this is the case when the v dd voltage has reached v ddon and remains above v ddoff . 2. this parameter applies when the start up current source is on. this is the case when the v dd voltage has not yet reached v ddon or has fallen below v ddoff . thermal data note: 1. when mounted on a standard single-sided fr4 board with 200 mm2 of cu (at least 35 m m thick) connected to all drain pins. electrical characteristics (t j =25c, v dd =18v, unless otherwise specified) power section note: 1. on clamped inductive load symbol parameter value unit v ds(sw) switching drain source voltage (t j =25 ... 125c) (see note 1) -0.3 ... 730 v v ds(st) start up drain source voltage (t j =25 ... 125c) (see note 2) -0.3 ... 400 v i d continuous drain current internally limited a v dd supply voltage 0 ... 50 v i fb feedback current 3 ma v esd electrostatic discharge: machine model (r=0 w ; c=200pf) charged device model 200 1.5 v kv t j junction operating temperature internally limited c t c case operating temperature -40 to 150 c t stg storage temperature -55 to 150 c symbol parameter max value unit rthj-case thermal resistance junction-pins for: so-8 dip8 25 15 c/w rthj-amb thermal resistance junction-ambient for: so-8 (see note 1) dip8 (see note 1) 55 45 c/w symbol parameter test conditions min. typ. max. unit bv dss drain-source voltage i d =1ma; v fb =2v 730 v i dss off state drain current v ds =500v; v fb =2v; t j =125c 0.1 ma r dson static drain-source on state resistance i d =0.2a i d =0.2a; t j =100c 27 30 54 w t f fall time i d =0.1a; v in =300v (see fig.1) (see note 1) 100 ns t r rise time i d =0.2a; v in =300v (see fig.1) (see note 1) 50 ns c oss drain capacitance v ds =25v 40 pf
viper12adip / viper12as 4/15 electrical characteristics (t j =25c, v dd =18v, unless otherwise specified) supply section note: 1. these test conditions obtained with a resistive load are leading to the maximum conduction time of the device. oscillator section pwm comparator section overtemperature section symbol parameter test conditions min. typ. max. unit i ddch start up charging current v ds =100v; v dd =5v ...v ddon (see fig. 2) -1 ma i ddoff start up charging current in thermal shutdown v dd =5v; v ds =100v t j > t sd - t hyst 0ma i dd0 operating supply current not switching i fb =2ma 35ma i dd1 operating supply current switching i fb =0.5ma; i d =50ma (note 1) 4.5 ma d rst restart duty cycle (see fig. 3) 16 % v ddoff v dd undervoltage shutdown threshold (see fig. 2 & 3) 7 8 9 v v ddon v dd start up threshold (see fig. 2 & 3) 13 14.5 16 v v ddhyst v dd threshold hysteresis (see fig. 2) 5.8 6.5 7.2 v v ddovp v dd overvoltage threshold 38 42 46 v symbol parameter test conditions min. typ. max. unit f osc oscillator frequency total variation v dd =v ddoff ... 35v; t j =0 ... 100c 54 60 66 khz symbol parameter test conditions min. typ. max. unit g id i fb to i d current gain (see fig. 4) 320 i dlim peak current limitation v fb =0v (see fig. 4) 0.32 0.4 0.48 a i fbsd i fb shutdown current (see fig. 4) 0.9 ma r fb fb pin input impedance i d =0ma (see fig. 4) 1.2 k w t d current sense delay to turn-off i d =0.2a 200 ns t b blanking time 500 ns t onmin minimum turn on time 700 ns symbol parameter test conditions min. typ. max. unit t sd thermal shutdown temperature (see fig. 5) 140 170 c t hyst thermal shutdown hysteresis (see fig. 5) 40 c
viper12adip / viper12as 5/15 figure 1 : rise and fall time figure 2 : start up vdd current figure 3 : restart duty cycle i d v ds 90% 10% t fv t rv t t l d 300v c fb vdd drain source control viper12a c << coss v dd v ddhyst v ddoff v ddon i dd0 i ddch v ds = 100 v f sw = 0 khz i dd t v dd v ddoff v ddon t ch t st d rst t st t st t ch + ------------------------- = 100v 10 m f fb vdd drain source control viper12a 2v
viper12adip / viper12as 6/15 figure 4 : peak drain current vs. feedback current figure 5 : thermal shutdown i fb 4mh 100v 100v 18v fb vdd drain source control viper12a 47nf g id i dpeak d i fb d ---------------------- - C = i d i dpeak t 1/f osc i fb i dpeak i dlim i fb i fbsd r fb v fb the drain current limitation is obtained for vfb = 0 v, and a negative current is drawn from the fb pin. see the application section for further details. 0 i fbsd t t v dd t j v ddon t sd t hyst automatic start up
viper12adip / viper12as 7/15 figure 6 : switching frequency vs temperature figure 7 : current limitation vs temperature -20 0 20 40 60 80 100 120 temperature (c) 0.97 0.98 0.99 1 1.01 normalized frequency vdd = 10v ... 35v -20 0 20 40 60 80 100 120 temperature (c) 0.94 0.95 0.96 0.97 0.98 0.99 1 1.01 1.02 1.03 1.04 normalized current limitation vin = 100v vdd = 20v
viper12adip / viper12as 8/15 figure 8 : rectangular u-i output characteristics for battery charger rectangular u-i output characteristic a complete regulation scheme can achieve combined and accurate output characteristics. figure 8 presents a secondary feedback through an optocoupler driven by a tsm101. this device offers two operational amplifiers and a voltage reference, thus allowing the regulation of both output voltage and current. an integrated or function performs the combination of the two resulting error signals, leading to a dual voltage and current limitation, known as a rectangular output characteristic. this type of power supply is especially useful for battery chargers where the output is mainly used in current mode, in order to deliver a defined charging rate. the accurate voltage regulation is also convenient for li-ion batteries which require both modes of operation. wide range of v dd voltage the v dd pin voltage range extends from 9v to 38v. this feature offers a great flexibility in design to achieve various behaviors. in figure 8 a forward configuration has been chosen to supply the device with two benefits: C as soon as the device starts switching, it immediately receives some energy from the auxiliary winding. c5 can be therefore reduced and a small ceramic chip (100 nf) is sufficient to insure the filtering function. the total start up time from the switch on of input voltage to output voltage presence is dramatically decreased. C the output current characteristic can be maintained even with very low or zero output voltage. since the tsm101 is also supplied in forward mode, it keeps the current regulation up whatever the output voltage is.the v dd pin voltage may vary as much as the input voltage, that is to say with a ratio of about 4 for a wide range application. t1 d3 c5 c4 -+ d4 c3 t2 f1 c1 c10 - + - + vref vcc gnd u2 tsm101 r6 r9 r10 r4 c9 r7 r5 r8 c8 r3 iso1 d2 d5 r2 c7 r1 c2 d1 fb vdd drain source cont rol u1 viperx2a c6 ac in dcout gnd
viper12adip / viper12as 9/15 feedback pin principle of operation a feedback pin controls the operation of the device. unlike conventional pwm control circuits which use a voltage input (the inverted input of an operational amplifier), the fb pin is sensitive to current. figure 9 presents the internal current mode structure. the power mosfet delivers a sense current i s which is proportional to the main current id. r2 receives this current and the current coming from the fb pin. the voltage across r2 is then compared to a fixed reference voltage of about 0.23 v. the mosfet is switched off when the following equation is reached: by extracting i s : using the current sense ratio of the mosfet g id : the current limitation is obtained with the fb pin shorted to ground (v fb = 0 v). this leads to a negative current sourced by this pin, and expressed by: by reporting this expression in the previous one, it is possible to obtain the drain current limitation i dlim : in a real application, the fb pin is driven with an optocoupler as shown on figure 9 which acts as a pull up. so, it is not possible to really short this pin to ground and the above drain current value is not achievable. nevertheless, the capacitor c is averaging the voltage on the fb pin, and when the optocoupler is off (start up or short circuit), it can be assumed that the corresponding voltage is very close to 0 v. for low drain currents, the formula (1) is valid as long as ifb satisfies i fb < i fbsd , where i fbsd is an internal threshold of the viper12a. if i fb exceeds this threshold the device will stop switching. this is represented on figure 4, and i fbsd value is specified in the pwm comparator section. actually, as soon as the drain current is about 12% of idlim, that is to say 50 ma, the device will enter a burst mode operation by missing switching cycles. this is especially important when the converter is lightly loaded. it is then possible to build the total dc transfer function between i d and i fb as shown on figure 10. this figure also takes into account the internal blanking time and its associated minimum turn on time. this imposes a minimum drain current under which the device is no more able to control it in a linear way. this drain current depends on the primary inductance value of the transformer and the input voltage. two cases may occur, depending on the value of this current versus the fixed 50 ma value, as described above. start up sequence this device includes a high voltage start up current source connected on the drain of the device. as soon as a voltage is applied on the input of the converter, this start up current source is activated as long as v dd is lower than v ddon . when reaching v ddon , the start up current source is switched off and the device begins to operate by turning on and off its main power mosfet. as the fb pin does not receive any current from the optocoupler, the device operates at full current capacity and the output voltage rises until reaching fi gure 9 : i nterna l c urrent c ontro l s tructure 60khz oscillator pwm latch s q r 0.23v id drain source fb r1 r2 c +vdd secondary feedback i fb is 1 k w 230 w r 2 i s i fb + () 0.23 v = i s 0.23 v r 2 -------------- i fb C = i d g id i s g id 0.23 v r 2 -------------- i fb C ? ?? == i fb 0.23 v r 1 -------------- C = i dlim g id 0.23 v 1 r 2 ----- - 1 r 1 ----- - + ? ?? = fi gure 10 : i fb t rans f er f unct i on i fbsd i dlim i fb t onmin v 2 in l -------------------------------------- - t onmin v 1 in l -------------------------------------- - 50ma i dpeak 0 part masked by the i fbsd threshold
viper12adip / viper12as 10/15 the regulation point where the secondary loop begins to send a current in the optocoupler. at this point, the converter enters a regulated operation where the fb pin receives the amount of current needed to deliver the right power on secondary side. this sequence is shown in figure 11. note that during the real starting phase t ss , the device consumes some energy from the v dd capacitor, waiting for the auxiliary winding to provide a continuous supply. if the value of this capacitor is too low, the start up phase is terminated before receiving any energy from the auxiliary winding and the converter never starts up. this is illustrated also in the same figure in dashed lines. overvoltage threshold an overvoltage detector on the v dd pin allows the viper12a to reset itself when v dd exceeds v ddovp . this is illustrated in figure 12, which shows the whole sequence of an overvoltage event. note that this event is only latched for the time needed by v dd to reach v ddoff , and then the device resumes normal operation automatically. fi gure 11 : st ar t u p s equence t t i fb v ddon t v out v dd v ddoff tss fi gure 12 : o vervo lt age s equence t t v ds v ddon v dd v ddoff v ddovp
viper12adip / viper12as 11/15 dim. mm. inch min. typ max. min. typ. max. a 1.75 0.068 a1 0.1 0.25 0.003 0.009 a2 1.65 0.064 a3 0.65 0.85 0.025 0.033 b 0.35 0.48 0.013 0.018 b1 0.19 0.25 0.007 0.010 c 0.25 0.5 0.010 0.019 c1 45 (typ.) d 4.8 5 0.188 0.196 e 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 3.81 0.150 f 3.8 4 0.14 0.157 l 0.4 1.27 0.015 0.050 m 0.6 0.023 s 8 (max.) l1 0.8 1.2 0.031 0.047 1 so-8 mechanical data
viper12adip / viper12as 12/15 dim. mm. min. typ max. a 5.33 a1 0.38 a2 2.92 3.30 4.95 b 0.36 0.46 0.56 b2 1.14 1.52 1.78 c 0.20 0.25 0.36 d 9.02 9.27 10.16 e 7.62 7.87 8.26 e1 6.10 6.35 7.11 e2.54 ea 7.62 eb 10.92 l 2.92 3.30 3.81 package weight gr. 470 p001 plastic dip-8 mechanical data
viper12adip / viper12as 13/15 1 so-8 tube shipment (no suffix) all dimensions are in mm. base q.ty 100 bulk q.ty 2000 tube length ( 0.5) 532 a 3.2 b 6 c ( 0.1) 0.6 tape and reel shipment (suffix 13tr) all dimensions are in mm. base q.ty 2500 bulk q.ty 2500 a (max) 330 b (min) 1.5 c ( 0.2) 13 f 20.2 g (+ 2 / -0) 12.4 n (min) 60 t (max) 18.4 tape dimensions according to electronic industries association (eia) standard 481 rev. a, feb 1986 all dimensions are in mm. tape width w 12 tape hole spacing p0 ( 0.1) 4 component spacing p 8 hole diameter d ( 0.1/-0) 1.5 hole diameter d1 (min) 1.5 hole position f ( 0.05) 5.5 compartment depth k (max) 4.5 hole spacing p1 ( 0.1) 2 top cover tape end start no components no components components 500mm min 500mm min empty components pockets saled with cover tape. user direction of feed reel dimensions c b a
viper12adip / viper12as 14/15 1 1 dip-8 tube shipment (no suffix) all dimensions are in mm. base q.ty 20 bulk q.ty 1000 tube length ( 0.5) 532 a 8.4 b 11.2 c ( 0.1) 0.8 a b c
viper12adip / viper12as 15/15 information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the co nsequences of use of such information nor for any infringement of patents or other rights of third parties which may results from its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specifications mentioned in this p ublication are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectron ics products are not authorized for use as critical components in life support devices or systems without express written approval of stmicr oelectronics. the st logo is a trademark of stmicroelectronics ? 2002 stmicroelectronics - printed in italy- all rights reserved. stmicroelectronics group of companies australia - brazil - canada - china - finland - france - germany - hong kong - india - israel - italy - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - u.s.a. http://www.st.com

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