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 . WS3252 WS3252 WS3252 WS3252 rev.a sep .201 1 features features features features 5 ua ultra-low startup current 2 ma low operating current 5% constant voltage regulation at universal ac input primary-side sensing and regulation without tl431 and opto-coupler programmable cv and cc regulation built-in primary winding inductance compensation programmable cable drop compensation built-in soft start built-in leading-edge blanking cycle by cycle over current protection (ocp) vcc over voltage clamp & under voltage lockout( uvlo) maximum gate output voltage clamped at 12v frequency jittering applications applications applications applications low power ac/dc offline smps for cell phone charger digital cameras charger small power adapter auxiliary power for pc, tv etc. linear regulator/rcc replacement typical typical typical typical application application application application circuit circuit circuit circuit WS3252 is a high-integrated offline pwm controller, optemized for high poformance low power ac/dc charger and adapter adapter application. WS3252 operates in primary-side sensing and regulation. consequently, opto-coupler and tl431 could be eliminated, thus reduce the cost. it can achieve 5% constant voltage precision in full input voltage range. cc/cv control as shown in fig.1.in cc control, the current and output power setting can be adjusted externally by the sense resistor rs at cs pin. in cv control, multi-mode operations are utilized to achieve high performance and high efficiency. in addition, good load regulation is achieved by the built-in cable drop compensation. device operates in pfm in cc mode as well at large load condition and it operates in pwm with frequency reduction at light/medium load. WS3252 offers power on soft start control and protection coverage with auto-recovery features including cycle-by-cycle current limiting, vcc ovp,vcc clamp and uvlo. the gate-driven output is clamped to maximum 12 v to protect the internal mosfet. excellent emi performance is achieved by using the soft-switching and frequency jittering at the totem-pole-gate-drive output. the WS3252 is the ideal substitute of the linear power supply or the rcc-mod e power , for a better performance of the whole switch power system and a lower cost. WS3252 is available in sot23-6 package. WS3252 high precision cc/cv primary-side pwm controller v o i o 5 % i c c general general general general description description description description
WS3252 WS3252 WS3252 WS3252 2 / 8 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance pin pin pin pin definition definition definition definition and and and and device device device device marking marking marking marking pin pin pin pin function function function function description description description description pin pin pin pin name name name name pin pin pin pin number number number number pin pin pin pin type type type type function function function function description description description description gnd 1 gnd ground. gate 2 gate-driven output totem-pole gate driver output for power mosfet. cs 3 current monitoring current sense input . inv 4 feedback input the voltage feedback from auxiliary winding. connected to resistor divider from auxiliary winding reflecting output voltage. pwm duty cycle is determined by ea output and current sense signal at pin3. comp 5 loop compensation loop compensation for cv stability vcc 6 power power supply block block block block diagram diagram diagram diagram 1 2 3 4 5 6 g n d g a t e c s i n v c o m p v c c sot 23-6 52 : WS3252 y: year code (0-9) ww: week code (1-52) 6 u v l o regulator v c c _o v p p o r inter supply 1 g n d g n d g n d g n d 2 driver g a t e g a t e g a t e g a t e 4 i n v i n v i n v i n v sampler sa m pling controller e a + - 2 v drop com p p w m & s s + - 5 3 c o m p c o m p c o m p c o m p c s c s c s c s v c c v c c v c c v c c l e b o c p l o g i c c c controller c l k generation
WS3252 WS3252 WS3252 WS3252 3 / 8 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance ordering ordering ordering ordering information information information information package package package package ic ic ic ic marking marking marking marking information information information information purchasing purchasing purchasing purchasing device device device device name name name name 6-pin sot23-6, pb-free WS3252tp WS3252tp recommended recommended recommended recommended operating operating operating operating condition condition condition condition symbol symbol symbol symbol parameter parameter parameter parameter value value value value unit unit unit unit vcc vcc supply voltage 10~30 v ta operating temperature -20~85 absolute absolute absolute absolute maximum maximum maximum maximum ratings ratings ratings ratings symbol symbol symbol symbol parameter parameter parameter parameter value value value value unit unit unit unit vcc dc supply voltage 30 v vinv inv input voltage -0.3~7 v vcs cs input voltage -0.3~7 v vcomp comp input voltage -0.3~7 v tj max. operating junction temperature 150 tstg min./max. storage temperature -55~150 icc vcc clamp continuous current 10 ma note note note note : stresses above those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, functional operation of the device at these or any other conditions beyond those indicated in the recommended operating conditions section are not implied. exposure to absolute maximum-rated conditions for extended periods may affect device reliability.
WS3252 WS3252 WS3252 WS3252 4 / 8 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance electrical electrical electrical electrical characteristics characteristics characteristics characteristics ( ta=25 vcc=16v, if not otherwise noted ) supply supply supply supply voltage voltage voltage voltage (vcc) (vcc) (vcc) (vcc) symbol parameter test condition min typ max unit i_vcc_st start up current vcc=13v 5 20 ua i_vcc_op operation current vcc=1 8 v, inv=2v , cs=0 v 2 3 ma uvlo_on turn on threshold voltage vcc falling 8.2 9.0 10 .5 v uvlo_off turn-off threshold voltage vcc rising 13.5 14. 8 1 6.0 v vcc_clamp vcc zener clamp voltage ivcc=10ma 28 29 31 v ovp over voltage protection threshold ramp vcc until gate shut down 27 28.3 30 v error error error error amplifier amplifier amplifier amplifier section section section section vref_ea reference voltage for ea 1.97 2 2.03 v gain dc gain of ea 60 db i_comp_max max. cable compensation current inv=2v,comp=0v 37.5 ua current current current current sense sense sense sense section section section section tleb leading edge blanking time 625 ns z sense input impedance 50 k ? t d _oc ocp control delay 110 ns v th _oc ocp threshold 0.88 0.91 0.94 v t_ss soft start time 17 ms oscillator oscillator oscillator oscillator section section section section freq_max 1 ic maximum frequency 55 60 65 khz freq_nom system nominal switch frequency 50 khz freq_startup inv=0v,comp=5v 14 khz ? f/freq frequency shuffling range 6 % gate gate gate gate driver driver driver driver output output output output section section section section vol output low level io=20ma 1 v voh output high level io=20ma 6 v v_clamp output clamp voltage level 12 v t_r output rising time cl=0.5nf 650 ns t_f output falling time cl=0.5nf 40 ns note note note note : 1. freq_max indicates ic internal maximum clock frequency. in system application, the maximum operation frequency of 60khz nominal occurs at maximum output power or the transition point from cv to cc.
WS3252 WS3252 WS3252 WS3252 5 / 8 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance typical typical typical typical operating operating operating operating characteristics characteristics characteristics characteristics
WS3252 WS3252 WS3252 WS3252 6 / 8 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance function function function function description description description description WS3252 is a high-integrated offline pwm controller, optemized for high poformance low power ac/dc charger and adapter adapter application. WS3252 operates in primary-side sensing and regulation. consequently, opto-coupler and tl431 could be eliminated, thus reduce the cost. high presicion cc/cv control can meet most adapter and charger application requirements. startup startup startup startup current current current current and and and and startup startup startup startup control control control control startup current of WS3252 is designed to be extremely low at 5ua, so that vcc could be charged up above uvlo threshold level and device starts up quickly. a large value startup resistor can therefore be used to minimize the power loss, predigest the design of startup circuit and provides reliable startup in application. operating operating operating operating current current current current the operating current of WS3252 is low at 2ma. excellent efficiency is achieved with low operating current together and multi-mode control circuit. cc/cv cc/cv cc/cv cc/cv operation operation operation operation WS3252 is designed to produce good cc/cv control characteristic as shown in the fig.1. in charger applications, a discharged battery charging starts in the cc portion of the curve until it is nearly full charged and smoothly switches to operate in cv portion of the curve. in an ac/dc adapter, the normal operation occurs only on the cv portion of the curve. the cc portion provides output current limiting. in cv operation, the output voltage is regulated through the primary side control. in cc operation mode, WS3252 will regulate the output current constant regardless of the output voltage drop. principle principle principle principle of of of of operation operation operation operation to achieve high precision cc/cv control, system needs to be designed in dcm mode for flyback system. in dcm mode, the output voltage can be sensed via the auxiliary winding. during mosfet turn-on time, the load current is supplied from the output filter capacitor co. the current in the primary winding ramps up. when mosfet turns off, the primary current transfers to the secondary at the amplitude of p s p s i n n i * = the auxiliary voltage reflects the output voltage, given by ) ( * v v n n v o s aux aux ? + = where v indicates the drop voltage of the output diode. via a resistor divider connectrd between the auxiliary winding and inv, the auxiliary voltage is sampled at the end of the demagnetization and it is hold until the next sampling. the sampled voltage is compared with vref(2v) and the error is amplified. the error amplifier output comp reflects the load condition and controls the pwm switching frequency to regulate the output voltage, thus the constant output current can be achieved. when sampled voltage is below vref and error amplifier output comp reaches its maximum, the switching frequency is controlled by the sampled voltage thus the output voltage to regulate the output current, thus the constant output current can be achieved. adjustable adjustable adjustable adjustable cc cc cc cc point point point point and and and and output output output output power power power power in WS3252, the cc point and maximum output power can be externally adjusted by eaternal current sense resistor rs at cs pin. the output power is adjusted through cc point change. the larger rs, the smaller cc point is, and the smaller output power becomes, and vice versa. fig.2 adjustable output power by changing rs v o i o large r s sm all r s
WS3252 WS3252 WS3252 WS3252 7 / 8 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance operation operation operation operation switching switching switching switching frequency frequency frequency frequency the switching frequency of WS3252 is adaptively controlled according to the load conditions and the operation modes. the operation switching frequency at maximum output power is set to 60khz internally. in dcm mode, the maximum output power is given by 2 2 1 p sw p omax i f l p = where lp indicate the inductance of primary winding and ip is peak current of primary winding. the change of the primary winding inductance results in the change of the maximum output power and constant output current in cc mode. to compensate the change from viariations of primary winding inductance, the switching frequency is locked by an internal loop such that the switching frequency is demag sw t f 2 1 = since tdemag is inversely proportional to the inductance, as a result, the product lp and fsw is constant, thus the maximum output power and constant current in cc mode will not change as primary winding inductance changes. up to 10% variation of the primary winding inductance can be compensation. frequency frequency frequency frequency shuffling shuffling shuffling shuffling excellent emi performance is achieved by using frequency jittering in WS3252 current current current current sensing sensing sensing sensing and and and and leading leading leading leading edge edge edge edge blanking blanking blanking blanking cycle-by-cycle current limiting is offered in WS3252. the switch current is detected by a sense resistor into the sense pin. an internal leading edge blanking circuit chops off the sense voltage spike at initial mosfet on state due to snubber diode reverse recovery so that the external rc filtering on sense input is no longer required. the current limit comparator is disabled and thus cannot turn off the internal mosfet during the blanking period. pwm duty cycle is determined by the current sense input voltage and the ea output voltage. programmable programmable programmable programmable cable cable cable cable drop drop drop drop compensation compensation compensation compensation cable drop compensation is implemented to achieve good load regulation inWS3252. an offset voltage is generated at inv by an internal current flowing into the resister divider. the current is inversely proportional to the voltage across pin comp, as a result, it is inversely proportional to the output load current, thus the drop due to the cable loss can be compensated. as the load current decreases from full-load to no-load, the offset voltage at inv will increase. it can also be programmed by adjusting the resistance of the divider to compensate the drop for various cable lines used. gate gate gate gate drive drive drive drive the gate drive strength which is too weak leads to over switch loss of mosfet while too strong gate drive output compromises in the over emi. a good tradeoff between output strength and dead time control is achieved through the design of the built-in totem pole gate. the low standby dissipation and good emi system design is easier to achieve through this dedicated devise. for mosfet gate protection, an internal 12v clamp is added at higher than expected vcc input. protection protection protection protection controls controls controls controls excellent system stability is achieved by the comprehensive protection of WS3252. including cycle-by-cycle current limiting (ocp), vcc clamp, under voltage lockout on vcc (uvlo). device restarts when vcc voltage drops below uvlo limit. it is clamped when vcc is higher than threshold value. the power mosfet is shut down when vcc drops below uvlo limit and device enters power on start-up sequence thereafter.
WS3252 WS3252 WS3252 WS3252 8 / 8 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance sot23-6 sot23-6 sot23-6 sot23-6 package package package package outline outline outline outline dimensions dimensions dimensions dimensions symbol dimensions in milimeters dimensions in inches min max min max a 1.000 1.300 0.039 0.051 a1 0.000 0.150 0.000 0.006 a2 1.000 1.200 0.039 0.047 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 d 2.800 3.020 0.110 0.119 e 1.500 1.700 0.059 0.067 e1 2.600 3.000 0.102 0.118 e 0.950(bsc) 0.037(bsc) e1 1.800 2.000 0.071 0.079 l 0.300 0.600 0.012 0.024 0 8 0 8
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