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november 2010 doc id 12050 rev 2 1/21 21 viper22a-e viper22adip-e, viper22as-e low power off-line smps primary switcher features fixed 60 khz switching frequency 9 v to 38 v 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 description the viper22a-e 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. figure 1. block diagram table 1. typical power capability mains type so-8 dip-8 european (195 - 265 vac) 12 w 20 w us / wide range (85 - 265 vac) 7 w 12 w dip-8 so-8 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 www.st.com
contents viper22a-e, vipe r22adip-e, viper22as-e 2/21 doc id 12050 rev 2 contents 1 electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 pin connections and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1 rectangular u-i output characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2 wide range of vdd voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.3 feedback pin principle of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.4 startup sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.5 overvoltage threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5 operation pictures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 7 order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 8 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
viper22a-e, viper22adip-e, viper22as-e electrical data doc id 12050 rev 2 3/21 1 electrical data 1.1 maximum ratings 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 imp lied. exposure to absolute ma ximum rating conditions for extended periods may affect device reliability. 1.2 thermal data table 2. absolute maximum rating symbol parameter value unit v ds(sw) switching drain source voltage (t j = 25 ... 125 c) (1) 1. this parameter applies when the start-up current source is off. this is the case when the vdd voltage has reached v ddon and remains above v ddoff . -0.3 ... 730 v v ds(st) start-up drain source voltage (t j = 25 ... 125 c) (2) 2. this parameter applies when the start up current source is on. this is the case when the vdd voltage has not yet reached v ddon or has fallen below v ddoff. -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 = 200 pf) 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 3. thermal data symbol parameter so-8 dip-8 unit r thjc thermal resistance junction - case max 25 15 c/w r thja thermal resistance junction - ambient (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 viper22a- e, viper22adip-e, viper22as-e 4/21 doc id 12050 rev 2 2 electrical characteristics t j = 25 c, v dd = 18 v, unless otherwise specified table 4. power section symbol parameter test conditions min typ max unit bv dss drain-source voltage i d = 1 ma; v fb = 2 v 730 v i dss off state drain current v ds = 500 v; v fb = 2 v; t j = 125 c 0.1 ma r ds(on) static drain-source on state re sistance i d = 0.4 a i d = 0.4 a; t j = 100 c 15 17 31 t f fall time i d = 0.2 a; v in = 300 v (1) (see figure 9 on page 13 ) 1. on clamped inductive load 100 ns t r rise time i d = 0.4 a; v in = 300 v (1) (see figure 9 on page 13 ) 50 ns c oss drain capacitance v ds = 25 v 40 pf table 5. supply section symbol parameter test co nditions min typ max unit i ddch start-up charging current 100 v v ds 400 v; v dd = 0 v ...v ddon (see figure 10 on page 13 ) -1 ma i ddoff start-up charging current in thermal shutdown v dd = 5 v; v ds = 100 v t j > t sd - t hyst 0 ma i dd0 operating supply current not switching i fb = 2 ma 3 5 ma i dd1 operating supply current switching i fb = 0.5 ma; i d = 50 ma (1) 1. these test conditions obtained with a resistive load are leading to t he maximum conduction time of the device. 4.5 ma d rst restart duty-cycle (see figure 11 on page 13 ) 16 % v ddoff v dd undervoltage shutdown threshold (see figure 10 , figure 11 on page 13 ) 7 8 9 v v ddon v dd start-up threshold (see figure 10 , figure 11 on page 13 )) 13 14.5 16 v v ddhyst v dd threshold hysteresis (see figure 10 on page 13 ) 5.8 6.5 7.2 v v ddovp v dd overvoltage threshold 38 42 46 v
viper22a-e, viper22adip-e, viper2 2as-e electrical characteristics doc id 12050 rev 2 5/21 table 6. oscillation section symbol parameter test co nditions min typ max unit f osc oscillator frequency total variation v dd = v ddoff ... 35 v; t j = 0 ... 100 c 54 60 66 khz table 7. pwm comparator section symbol parameter test co nditions min typ max unit g id i fb to i d current gain (see figure 12 on page 14 ) 560 i dlim peak current limitation v fb = 0 v (see figure 12 on page 14 ) 0.56 0.7 0.84 a i fbsd i fb shutdown current (see figure 12 on page 14 ) 0.9 ma r fb fb pin input impedance i d = 0 ma (see figure 12 on page 14 ) 1.2 k t d current sense delay to turn-off i d = 0.4 a 200 ns t b blanking time 500 ns t onmin minimum turn-on time 700 ns table 8. overtemperature section symbol parameter test co nditions min typ max unit t sd thermal shutdown temperature (see figure 13 on page 14 ) 140 170 c t hyst thermal shutdown hysteresis (see figure 13 on page 14 ) 40 c table 9. typical power capability (1) 1. above power capabilities are gi ven under adequate thermal conditions mains type so-8 dip-8 european (195 - 265 vac) 12 w 20 w us / wide range (85 - 265 vac) 7 w 12 w
pin connections and function viper2 2a-e, viper22adip-e, viper22as-e 6/21 doc id 12050 rev 2 3 pin connections and function figure 2. pin connection figure 3. current and voltage conventions table 10. 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 connect ed to the drain. for this purpose, an hysteresis comparator monitors the v dd voltage and provides two thresholds: - v ddon : voltage value (typically 14.5 v) at which the device starts switching and turns off the start up current source. - v ddoff : voltage value (typically 8 v) 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 0 v to 1 v, 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 viper22a
viper22a-e, viper22adip-e, viper22as-e operations doc id 12050 rev 2 7/21 4 operations 4.1 rectangular u-i ou tput characteristics figure 4. rectangular u-i output characteristics for battery charger a complete regulation scheme can achieve combined and accurate output characteristics. figure 4. 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. 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 control u1 viperx2a c6 ac in dcout gnd
operations viper22a-e, vipe r22adip-e, viper22as-e 8/21 doc id 12050 rev 2 4.2 wide range of v dd voltage the v dd pin voltage range extends from 9 v to 38 v. this feature offers a great flexibility in design to achieve various behaviors. in figure 4 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 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. 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. 4.3 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 5. presents the internal current mode structure. figure 5. internal current control structure
viper22a-e, viper22adip-e, viper22as-e operations doc id 12050 rev 2 9/21 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 5. 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 viper22a. if i fb exceeds this threshold the device will stop switching. this is represented on figure 12 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 85 ma, the device will ente r a burst mode operation by missing switching cycles. this is especially important when the converter is lightly loaded. 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 ? ?? ?? ? == i fb 0.23v r 1 --------------- - ? = i dlim g id 0.23v 1 r 2 ------ - 1 r 1 ------ - + ?? ?? ?? =
operations viper22a-e, vipe r22adip-e, viper22as-e 10/21 doc id 12050 rev 2 figure 6. 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 6 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 85 ma value, as described above. i fbsd i dlim i fb t onmin v 2 ? in l ---------------------------------------- - t onmin v 1 ? in l ---------------------------------------- - 85ma i dpeak 0 part masked by the i fbsd threshold
viper22a-e, viper22adip-e, viper22as-e operations doc id 12050 rev 2 11/21 4.4 startup sequence figure 7. 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 7 . note that during the real starting phase t ss , the device consumes some energy from the v dd capacitor, waiting for the au xiliary 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.
operations viper22a-e, vipe r22adip-e, viper22as-e 12/21 doc id 12050 rev 2 4.5 overvoltage threshold an overvoltage detector on the v dd pin allows the viper22a to reset itself when v dd exceeds v ddovp . this is illustrated in figure 8. 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 8. overvoltage sequence t t v ds v ddon v dd v ddoff v ddovp
viper22a-e, viper22adip-e, vi per22as-e operation pictures doc id 12050 rev 2 13/21 5 operation pictures figure 9. rise and fall time figure 10. start-up v dd current figure 11. restart duty-cycle i d v ds 90% 10% t fv t rv t t l d 300v c fb vdd drain source control viper22a c << coss v dd v ddhyst v ddoff v ddon i dd0 i ddch 100 v v ds 400 v f sw = 0 khz i dd 100v 10 f fb vdd drain source control viper22a 2v t v dd v ddoff v ddon t ch t st d rst t st t st t ch + -------------------------- - =
operation pictures viper22a-e, viper22adip-e, viper22as-e 14/21 doc id 12050 rev 2 figure 12. peak drain current vs feedback current figure 13. thermal shutdown i fb 4mh 100v 100v 18v fb vdd drain source control viper22a 47nf g id i dpeak i fb ------------------------ ? = 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
viper22a-e, viper22adip-e, vi per22as-e operation pictures doc id 12050 rev 2 15/21 figure 14. switching frequency vs temperature figure 15. current limi tation vs temperature
package mechanical data viper22a -e, viper22adip-e, viper22as-e 16/21 doc id 12050 rev 2 6 package mechanical data in order to meet environmental requirements, st offers these devices in different grades of ecopack ? packages, depending on their level of environmental compliance. ecopack ? specifications, grade definitions and product status are available at: www.st.com . ecopack is an st trademark.
viper22a-e, viper22adip-e, vipe r22as-e package mechanical data doc id 12050 rev 2 17/21 figure 16. package dimensions table 11. dip-8 mechanical data dim. databook (mm.) min. nom. 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
package mechanical data viper22a -e, viper22adip-e, viper22as-e 18/21 doc id 12050 rev 2 figure 17. package dimensions table 12. so-8 mechanical data dim. databook (mm. min. nom. 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
viper22a-e, viper22adip-e, viper22as-e order codes doc id 12050 rev 2 19/21 7 order codes table 13. order codes order codes package packaging viper22astr-e so-8 tape and reel viper22as-e so-8 tube viper22adip-e dip-8 tube
revision history viper22a-e, viper22adip-e, viper22as-e 20/21 doc id 12050 rev 2 8 revision history table 14. document revision history date revision changes 09-feb-2006 1 initial release. 25-nov-2010 2 updated ta b l e 1 1 .
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