w s34 4 1 a productdescription winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics c o p y r igh t @ w i n s em i microelectronics c o . , lt d . , a l l ri g h t r e s er v ed 1105 features ? critical conduction mode operation ? internal 500v power mosfet ? no auxiliary winding ? ultra low operating current ? 3 % led output current accuracy ? efficiency up to 93% ? led open protection ? led short protection ? current sensi ng resistor short protection ? thermal regulation function ? available in sop-8 package applications ? led candle light ? led bulb, spot light ? t8/t10 led string ? other led lighting description the ws3441 a is a high precision buck constant current led driver. the device operates in critical conduction mode and is suitable for 85vac~265vac universal input offline led lighting. the ws3441 a integrates a 500v power mosfet. t he operating current of the ic is very low . s o it doesn t need the auxiliary winding for supplying the chip. i t can achieve excellent constant current performance with very few external components, so the system cost and size are minimized . the ws3441 a utilizes patent pending current control method. it can achieve precise output current and excellent line regulation. the driver operates in critical conduction mode , t he output current does not change with the inductance and led output voltage. the ws3441 a offers rich protection functions to improve the system reliability, including led open circuit protection, led short circuit protection, vcc under voltage protection, cs resistor short circuit protection and thermal regulation function. the ws3441 a is a vailable in sop-8 package . typical application attention a 22pf capacitor can be parallel with rovp and a resistor can be parallel with the vcc capacitor. non-isolated buck offline led driver
www.winsemi.com tel : +86-755-8250 6288 fax : +86-755-8250 6299 2 / 8 w s34 4 1 a productdescription winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics pin configuration and marking information the ws3441a is available in sop-8 package the top marking is sho wn as below: pin definition name pin no. description gnd 1 ground rovp 2 over voltage protection setting pin. connect a resistor to gnd nc 3 no connection. should be connected to gnd(pin1) vcc 4 power supply pin drain 5 /6 internal hv power mosfet drain. cs 7 /8 current sense pin . connect a sens e resistor between this pin and gnd pin. internal block diagram ws 34 41a s 8 p a product code x internal code bcy internal code for qc y mx d/c
www.winsemi.com tel : +86-755-8250 6288 fax : +86-755-8250 6299 3 / 8 w s34 4 1 a productdescription winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics ordering information package marking part number 8-pin sop-8, pb-free WS3441AS8P WS3441AS8P recommended operation conditions part number package input voltage maximum output power ws 3441as 8p sop8 175vac-264vac 150v/120ma 90vac-264vac 6 0v/1 5 0ma absolute maximum ratings symbol paramete range unit v ds internal hv mosfet drain voltage -0.3~500 v i cc_max vcc pin maximum sink current 2.5 v v rovp over-voltage setting pin voltage -0.3~7 v v source internal hv mosfet source voltage -0.3~8 v v cs current sense pin input voltage -0.3~7 v p dmax power dissipation 0.5 w t j operating junction temperature 165 t stg storage temperature range -55~165 note : stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device.
www.winsemi.com tel : +86-755-8250 6288 fax : +86-755-8250 6299 4 / 8 w s34 4 1 a productdescription winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics electrical characteristics (unless otherwise specified, vcc= 7 v and ta =25 ) symbol parameter conditions min typ max units supply voltage section v cc_clamp vcc clamp voltage ivcc=1ma 7.3 v i cc_clamp vcc clamp current 2.5 ma v cc_st vcc turn on threshold vcc rising 6.9 v v uvlo_hys vcc turn off hysteresis vcc falling 1.5 v i st vcc startup current vcc w s34 4 1 a productdescription winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics www.winsemi.com tel : +86-755-8250 6288 fax : +86-755-8250 6299 5 / 8 application information the ws344 1a is a high performance non-isolated buck converter specially designed for led lighting. the device integrates a 500v power mosfet. with very few external components, the converter achieves excellent constant current control. and it does not need auxiliary winding for powering the ic or voltage sensing, hence the system size and cost is greatly reduced. start up after system powered up, the vcc pin capacitor is charged up by the start up resistor. when the vcc pin voltage reaches the turn on threshold, the internal circuits start operating. t he ws344 1a integrates a 17v zener diode to clamp the vcc voltage. due to the ultra-low operati ng current , the auxiliary winding is not needed to supply the ic. t he maximum value of the startup current is 270ua. for the application of 176vac 264vac, the startup resistor can be be calculated by the equatio n : _ min _ max 1.414 176 1.414 920k 270 in st st v v r i ua ? ? ? ? ? ? constant current control cycle by cycle current sense is adopted in ws3441 a, the cs pin is connected to the current sense comparator, and the voltage on cs pin is compared with the internal 400mv reference voltage . t he mosfet will be switched off when the voltage on cs pin reaches the threshold. the cs comparator includes a 350ns leading edge blanking time. the peak inductor current is given by: ) ma ( r 400 i cs pk ? where, rcs is the current sense resistor value. the current in led can be calculated by the equation: 2 i i pk led ? where, ipk is the peak current of the inductor. inductor selection the ws344 1a works under inductor current critical conduction mode. when the power mofet is switched on, the current in the inductor rises up from zero, the on time of the mosfet can be calculated by the equation: led in pk on v v i l t ? ? ? where, l is the inductance value vin is the dc bus voltage after the rectifier bridge vled is the voltage on the led after the power mosfet is switched off, the current in the inductor decreases . w hen the inductor current reaches zero, the power mosfet is turned on again by ic internal logic. the off time of the mosfet is given by: led pk off v i l t ? ? the inductance can be calculated by the equation: in pk led in led v i f ) v v ( v l ? ? ? ? ? t he f is the system switching frequency , which is proportional to the input voltage. so the minimum switching frequency is set at lowest input voltage, and the maximum switching frequency is set at highest input voltage. the minimum and maximum off time of ws344 1a is set at 3 us and 3 40us, respectively. referring to the equation of toff c alculation, if the inductance is too small, the toff may be smaller than the minimum off time, system will operate in discontinuous conduction mode and the output current will be smaller than the designed value. i f the inductance is too large, the toff may be larger than the maximum off time, the system will operate in continuous conduction mode and the output current will be higher than the designed value. so it is important to choos e a proper induct ance . over voltage protection the o ver voltage protection can be programmed by the rovp pin resistor. the rovp pin voltage is 0.5v. when the led is open circuit , the output voltage increases gradually, and the demagnetization time gets shorter. the d emagnetization time at ovp---- tovp can be calculated by the open circuit protection voltage : vovp rcs vcs l tovp ? ? ? where vcs is the cs pin turn off threshold (400mv) vovp is the open circuit protection voltage
www.winsemi.com tel : +86-755-8250 6288 fax : +86-755-8250 6299 6 / 8 winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics w s34 4 1 a productdescription and then the rovp resistor value can be calculated by the equation: 6 3.3* *10 rovp tovp ? kohm protection function the ws344 1a offers rich protection functions to improve the system reliability , i ncluding led open/short protection, cs resistor short protection, vcc under voltage protection, thermal regulation. when the led is open circuit , the system will trigger the over voltage protection and stop switching. when the led short circuit is detected, the system works at low frequency (5khz), and the cs pin turn off threshold is reduced to 200mv . s o the system power consumption is very low. at some catastrophic fault condition, such as cs resistor short ed or inductor s aturated , the internal fast fault detection circuit will be triggered, the system stops switching immediately. after the system enters into fault condition, the vcc voltage will decrease until it reaches the uvlo threshold , t hen the system will re-start again. if the fault condition is removed, the system will recover to normal operation. thermal regulation the ws344 1a integrates thermal regulation function. when the system is over temperature, the output current is gradually reduced; the output power and thermal dissipation are also reduced. the system temperature is regulated and the system reliability is improved. the thermal regulation temperature is set to 150 internally. pcb layouts the following rules should be followed in ws344 1a pcb layout: vcc capacitor the bypass capacitor on vcc pin should be as close as possible to the vcc pin and gnd pin. rovp pin the rovp resistor should be as close as possible to the rovp pin. ground path the power ground path for current sense should be short, and the power ground path should be separated from small signal ground path before connecting to the negative node of the bulk capacitor. the area of power loop the area of main current loop should be as small as possible to reduce emi radiation, such as the inductor, the power mosfet, the output diode and the bus capacitor loop. nc pin the nc pin should be connected to gnd ( pin1) . drain pin to i ncrease the copper area of drain pin for better thermal dissipation. however too large copper area may compromise emi performance. t he material of pcb avoid choosing the material that is easy to absor b the moisture , just like paper copper-clad laminates .
w s34 4 1 a productdescription winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics www.winsemi.com tel : +86-755-8250 6288 fax : +86-755-8250 6299 7 / 8 package information sop 8 package outline dimensions winsemi symbol dimensions in millimeters dimensions in inches min max min max a 4.70 5.10 0.185 0.201 b 3.70 4.10 0.146 0.161 c 1.30 1.50 0.051 0.059 a1 0.35 0.48 0.014 0.019 a2 1.27typ 0.05typ a3 0.345typ 0.014typ b1 5.80 6.20 0.228 0.244 b2 5.00typ 0.197typ c1 0.55 0.70 0.022 0.028 c2 0.55 0.70 0.022 0.028 c3 0.05 0.225 0.002 0.009 c4 0.203typ 0.008typ d 1.05typ 0.041typ d1 0.40 0.80 0.016 0.031 a b a1 a2 a3 0.5 * 0.125 0 05 . b 1 d c4 c 3 c 1 c c 2 r2 r1 1 b 2 3 2 4 d 1
www.winsemi.com tel : +86-755-8250 6288 fax : +86-755-8250 6299 8 / 8 winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics winsemi microelectronics w s34 4 1 a productdescription n ote: 1. we strongly recommend customers check carefully on the trademark when buying our product, if there is any question, please don't be hesitate to contact us. 2. please do not exceed the absolute maximum ratings of the device when circuit designing. 3. winsemi microelectronics co., ltd reserved the right to make changes in this specification sheet and is subject to change without prior notice. contact: winsemi microelectronics co., ltd. add:futian district, shenzhen tian an cyber tech plaza two east wing 1002 post code : 518040 tel : +86-755-8250 6288 fax : +86-755-8250 6299 web site : www.winsemi.com
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