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january 2006 docrev1 1/21 21 viper12adip - e viper12as - e low power off-line smps primary switcher features fixed 60khz switching frequency 9v to 38v wide range v dd voltage current mode control auxiliary undervoltage lockout with hysteresis high voltage start-up current source overtemperature, overcurrent and overvoltage protection with auto-restart typical power capability ? european (195 - 265 vac) 8w for so-8, 13w for dip-8 ? european (85 - 265 vac) 5w for so-8, 8w for dip-8 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: ? 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. ? automatic burst mode in low load condition. ? overvoltage protection in hiccup mode. dip-8 so-8 www.st.com 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 ? 42v _ + r2 ff s r q 230 ?
contents viper12adip/ as - e 2/21 docrev1 contents 1 electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 maximum rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 pin connections and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 rectangular u-i output characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 wide range of vdd voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6 feedback pin principle of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7 startup sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8 overvoltage threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9 operation pictures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 10 mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 11 order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 12 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
viper12adip/ as - e electrical data docrev1 3/21 1 electrical data 1.1 maximum rating stressing the device above the rating listed in the ?absolute maximum ratings? table may cause permanent damage to the device. these are stress ratings only and operation of the device at these or any other conditions above those indicated in the operating sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. refer also to the stmicroelectronics sure program and other relevant quality documents. 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 . 1.2 thermal data table 1. absolute maximum rating symbol parameter value unit v ds(sw) switching drain source voltage (t j = 25 ... 125c) note 1 -0.3 ... 730 v v ds(st) start-up drain source voltage (t j = 25 ... 125c) 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 ? ; 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 table 2. thermal data symbol parameter so-8 dip-8 unit r thjc thermal resistance junction-case max 25 15 c/w r thja thermal resistance ambient-case (1) 1. when mounted on a standard single-sided fr4 board with 200 mm 2 of cu (at least 35 m thick) connected to all drain pins. max 55 45 c/w
electrical characteristics viper12adip/ as - e 4/21 docrev1 2 electrical characteristics t j = 25c, v dd = 18v, unless otherwise specified note: 1 on clamped inductive load 2 these test conditions obtained with a resistive load are leading to the maximum conduction time of the device. table 3. power section 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 ds(on) static drain-source on state resistance i d = 0.2a i d = 0.2a; t j = 100c 27 30 54 ? t f fall time i d = 0.1a; v in = 300v note 1 (see figure 8 on page 13 ) 100 ns t r rise time i d = 0.2a; v in = 300v note 1 (see figure 8 on page 13 ) 50 ns c oss drain capacitance v ds = 25v 40 pf table 4. supply section symbol parameter test conditions min. typ. max. unit i ddch start-up charging current v ds = 100v; v dd = 5v ...v ddon (see figure 9 on page 13 ) -1 ma i ddoff start-up charging current in thermal shutdown v dd = 5v; v ds = 100v t j > t sd - t hyst 0 ma i dd0 operating supply current not switching i fb = 2ma 3 5 ma i dd1 operating supply current switching i fb = 0.5ma; i d = 50ma note 2 4.5 ma d rst restart duty-cycle (see figure 10 on page 13 ) 16 % v ddoff v dd undervoltage shutdown threshold (see figure 9 , figure 10 on page 13 ) 7 8 9 v v ddon v dd start-up threshold (see figure 9 , figure 10 on page 13 )) 13 14.5 16 v v ddhyst v dd threshold hysteresis (see figure 9 on page 13 ) 5.8 6.5 7.2 v v ddovp v dd overvoltage threshold 38 42 46 v
viper12adip/ as - e electrical characteristics docrev1 5/21 table 5. oscillation section 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 table 6. pwm comparator section symbol parameter test conditions min. typ. max. unit g id i fb to i d current gain (see figure 11 on page 14 ) 320 i dlim peak current limitation v fb = 0v (see figure 11 on page 14 ) 0.32 0.4 0.48 a i fbsd i fb shutdown current (see figure 11 on page 14 ) 0.9 ma r fb fb pin input impedance i d = 0ma (see figure 11 on page 14 ) 1.2 k ? 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 table 7. overtemperature section symbol parameter test conditions min. typ. max. unit t sd thermal shutdown temperature (see figure 12 on page 14 ) 140 170 c t hyst thermal shutdown hysteresis (see figure 12 on page 14 ) 40 c table 8. typical power capability mains type so-8 dip-8 european (195 - 265 vac) 8w 13w us / wide range (85 - 265 vac) 5w 8w
pin connections and function viper12adip/ as - e 6/21 docrev1 3 pin connections and function figure 1. pin connection figure 2. current and voltage conventions table 9. pin function pin name pin 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. 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 dip-8 i dd i d i fb v dd v fb v d fb vdd drain source control viper12a
viper12adip/ as - e rectangular u-i output characteristics docrev1 7/21 4 rectangular u-i output characteristics figure 3. rectangular u-i output characteristics for battery charger a complete regulation scheme can achieve combined and accurate output characteristics. figure 3. 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 vdd voltage viper12adip/ as - e 8/21 docrev1 5 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 3 on page 7 a forward configuration has been chosen to supply the device with two benefits: as soon as the device starts switching, it immediately receives some energy from the auxiliary windi ng. c5 can be therefore reduced and a small ceramic chip (100nf) 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. 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.
viper12adip/ as - e feedback pin principle of operation docrev1 9/21 6 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 4. presents the internal current mode structure. figure 4. internal current control 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 0.23v. 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 : r 2 i s i fb + () ? 0.23v = i s 0.23v r 2 --------------- - i fb ? = i d g id i s ? g id 0.23v r 2 --------------- - i fb ? ?? ?? ? ==
feedback pin principle of operation viper12adip/ as - e 10/21 docrev1 the current limitation is obtained with the fb pin shorted to ground (v fb = 0v). 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 4. 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 0v. 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 11 on page 14 , 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. figure 5. i fb transfer function it is then possible to build the total dc transfer function between i d and i fb as shown on figure 5 on page 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 50ma value, as described above. i fb 0.23v r 1 --------------- - ? = i dlim g id 0.23v 1 r 2 ------ - 1 r 1 ------ - + ?? ?? ?? =
viper12adip/ as - e startup sequence docrev1 11/21 7 startup sequence figure 6. startup 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 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 6 . 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 viper12adip/ as - e 12/21 docrev1 8 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 7. , 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. figure 7. overvoltage sequence t t v ds v ddon v dd v ddoff v ddovp
viper12adip/ as - e operation pictures docrev1 13/21 9 operation pictures figure 8. rise and fall time figure 9. start-up v dd current figure 10. restart duty-cycle
operation pictures viper12adip/ as - e 14/21 docrev1 figure 11. peak drain current vs. feedback current figure 12. thermal shutdown
viper12adip/ as - e operation pictures docrev1 15/21 figure 13. switching frequency vs. temperature figure 14. current limitation vs. temperature
mechanical data viper12adip/ as - e 16/21 docrev1 10 mechanical data in order to meet environmental requirements, st offers these devices in ecopack ? packages. these packages have a lead-free second level interconnect. the category of second level interconnect is marked on the package and on the inner box label, in compliance with jedec standard jesd97. the maximum ratings related to soldering conditions are also marked on the inner box label. ecopack is an st trademark. ecopack specifications are available at: www.st.com .
viper12adip/ as - e mechanical data docrev1 17/21 figure 15. package dimensions table 10. dip8 mechanical data dimensions ref. databook (mm) nom. min 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
mechanical data viper12adip/ as - e 18/21 docrev1 figure 16. package dimensions table 11. so8 mechanical data dimensions ref. databook (mm) nom. min max a 1.35 1.75 a1 0.10 0.25 a2 1.10 1.65 b 0.33 0.51 c 0.19 0.25 d 4.80 5.00 e 3.80 4.00 e 1.27 h 5.80 6.20 h 0.25 0.50 l 0.40 1.27 k 8 (max.) ddd 0.1
viper12adip/ as - e order codes docrev1 19/21 11 order codes table 12. order codes part number package shipment viper12astr-e so-8 tape and reel viper12as - e so-8 tube viper12adip - e dip-8 tube
revision history viper12adip/ as - e 20/21 docrev1 12 revision history table 13. document revision history date revision changes 09-jan-2006 1 initial release.
viper12adip/ as - e revision history docrev1 21/21 i nformation furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the con sequence s o f use of such information nor for any infringement of patents or other rights of third parties which may result from its use. n o license is grante d b y implication or otherwise under any patent or patent rights of stmicroelectronics. specifications mentioned in this publicatio n are subjec t t o change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectronics produ cts are no t authorized for use as critical components in life support devices or systems without express written approval of stmicroelectro nics. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners ? 2006 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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