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 . WS2273 WS2273 WS2273 WS2273 rev.a oct .201 1 features features features features burst mode control 5ua ultra-low startup current 1.8ma low operating current built-in leading-edge blanking built-in synchronous slope compensation circuit built-in soft-start 65khz fixed swith frequency cycle by cycle over current protection (ocp) vcc over voltage clamp & under voltage lockout( uvlo) over load protection (olp) otp and ovp shut down latch maximum gate output voltage clamped at 12v frequency jittering adjustable ovp through external zener applications applications applications applications universal switch power supply equipment and offline ac/dc flyback power converter power adapter set-top box power supplies open-frame smps battery charger typical typical typical typical application application application application circuit circuit circuit circuit 2273 is a high performance current mode pwm controller, optimized for low power power switch equipment. for lower the standby power and higher rohs compliant, the ic offers a burst mode control feature and ultra-low start-up current and operating current, that is, at the condition of no load or light load, 2273 can reduce the switch frequency linearly which minimize the switching power loss; the ultra-low startup current and operating current make a reliable power for startup design, and also large resistor can be used in the startup circuit to improve switching efficiency. the internal synchronous slope compensation circuit reduces the possible subharmonic oscillation at high pwm duty cycle output. leading-edge blanking on current sense(cs) input removes the signal glitch due to snubber diode circuit reverse recovery and thus greatly reduces the external component count and system cost in the design. 2273 offers comprehensive protection coverage with automatic self-recovery feature, including cycle by cycle over current protection (ocp), over load protection (olp),vcc clamp, under voltage lockout (uvlo), otp and ovp shut down latch. the gate-driven output is clamped to maximum 12v 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 tone energy at below 20khz is minimized in the design and audio noise is eliminat- ed during operation. the 2273 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. 2273 is available in sot23-6 package. 2273 current mode pwm controller general general general general description description description description
WS2273 WS2273 WS2273 WS2273 2 / 9 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. fb 2 feedback input feedback input pin. the pwm duty cycle is determined by voltage level into this pin and the current-sense signal at pin 4. the internal protection circuit will automatically shutdown when the fb voltage level exceeds a preset threshold voltage. rt 3 otp setting dual function pin. either connected through a ntc resistor to ground for over temperature shut down/latch control or connected through zener to vcc for adjustable over voltage protection. cs 4 current monitoring current sense input. vcc 5 power power supply gate 6 gate-driven output totem-pole gate driver output for power mosfet. block block block block diagram diagram diagram diagram 73 : WS2273 y: year code (0-9) ww: week code (1-52) s o f t s t a r t 2 m o d e s e l e c t o l p 4 1 6 s of t d r i v e r inter 5v supply t i m e r l o g i c f a u l t management f b c s g n d g a t e 3 r t l e b trimmed voltage/ current reference internal reference o t p 5 u v l o regulator vcc_ovp p o r v c c
WS2273 WS2273 WS2273 WS2273 3 / 9 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 73 xx 2273tp sot23-6 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 rt rt resistor value 100 kohm 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 vfb fb input voltage -0.3~7 v vcs cs input voltage -0.3~7 v vrt rt input voltage -0.3~7 v tj operating junction temperature -20~150 tstg storage temperature -40~150 vcv vcc clamp voltage 26 v icc vcc dc clamp current 10 ma 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.
WS2273 WS2273 WS2273 WS2273 4 / 9 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 symbol symbol symbol parameter parameter parameter parameter test test test test condition condition condition condition min min min min typ typ typ typ max max max max unit unit unit unit vcc_op operation voltage 30 v uvlo_on turn on threshold voltage 6 7 8 v uvlo_off turn-off threshold voltage 12.5 13.5 14.5 v i_vcc_st start up current vcc=13v 5 20 ua i_vcc_op operation current vfb=3v 1.8 2.5 ma vpull_up pull-up pmos active 13 vcc_clamp vcc zener clamp voltage ivcc=10ma 30 32 34 v ovp(on) over voltage protection voltage cs=0.3v,fb=3v, ramp up vcc until gate clock is off 26 28 30 vlatch_release latch release voltage 5 feedback feedback feedback feedback input input input input section section section section vfb_open vfb open loop voltage 3.9 4.2 v avcs pwm input gain vfb/ vcs 2 v/v vref_green the threshold enter green mode 2.1 v vref_burst_h the threshold exit burst mode 1.3 v vref_burst_l the threshold enter burst mode 1.2 v ifb_short fb pin short current fb shorted to gnd 0.4 ma vth_pl power limiting fb threshold 3.7 v td_pl power limiting debounce 80 88 96 ms zfb_in input impedance 16 k ? max_duty maximum duty cycle 75 80 85 % current current current current cs cs cs cs section section section section sst soft start time 4 ms tleb leading edge blanking time 220 ns zcs input impedance 40 k ? td_oc ocp control delay gate with 1nf to gnd 120 ns vth_oc ocp threshold fb 3v 0.75 v vocp_clamping 0.9 v oscillator oscillator oscillator oscillator section section section section fosc normal oscillation frequency vcc=14v,fb=3v,cs=0.3v 60 65 70 khz fosc_bm burst mode frequency 22 khz ? f_temp frequency variation versus temp. deviation temp = -20 to 85 1 % ? f_vcc frequency variation versus vcc vcc = 12 to 25v 1 % f_shuffling shuffling frequency 32 hz ? f_osc frequency jittering 4 %
WS2273 WS2273 WS2273 WS2273 5 / 9 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance gate gate gate gate output output output output section section section section vol output voltage low vcc = 14v, io = -5ma 1 v voh output voltage high vcc = 14v, io = 20ma 6 v vclamp output clamp voltage 12 v tr rising time gate with 1nf to gnd gate 1~12v 175 ns tf falling time gate with 1nf to gnd gate 12~1v 85 ns over over over over temperature temperature temperature temperature protection protection protection protection irt output current of rt pin 95 100 105 ua votp threshold voltage for otp 0.95 1 1.05 v td_otp otp debounce time 16 cycl e vrt_fl float voltage at rt pin 2.3 v vth_ovp external ovp threshold voltage 4 v
WS2273 WS2273 WS2273 WS2273 6 / 9 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
WS2273 WS2273 WS2273 WS2273 7 / 9 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance function function function function description description description description 2273 is a high performance current mode pwm controller, optimized for low power ac/dc application. ultra low startup current and operating current together with burst mode feature minimize the standby power consumption and improve the switching efficiency. in addition to reduce the external component count, the internal synchronous slope compensation combines with the leading-edge blanking improves system large stability and reduces the possible subharmonic oscillation. 2273 also have multiform general recovery protection mode. the main function is described as below . startup startup startup startup current current current current and and and and startup startup startup startup control control control control startup current of 2273 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. for the design of ac/dc adaptor with universal input range, a startup resistor of 2 m ? , 1/8 w could be used together with a vcc capacitor to provide a fast startup and low power dissipation solution. operating operating operating operating current current current current the operating current of 2273 is low at 1.8ma. excellent efficiency is achieved with low operating current together and extended burst mode control circuit. soft soft soft soft start start start start 2273 features an internal 4ms soft start to soften the electrical stress occurring in the power supply during startup. it is activated during the power on sequence. as soon as vcc reaches uvlo off the cs peak voltage is gradually increaced from 0.15v to the maximum level. every restart up is followed by a soft start. extended extended extended extended burst burst burst burst mode mode mode mode operation operation operation operation at zero load or light load, most of the power dissipation of the switching power supply comes from the mosfet switching loss, the core loss of the transformer and the loss on the snubber circuit. the magnitude of power loss is in proportion to the number of switching events within a period of time. therefore reducing the switch event leads to reduction on the power loss and thus saving the energy. for the burst mode control circuit, 2273 self adjusts the switching mode according to the loading condition. at the condition of no load or light/medium load, the fb input voltage drops below burst mode threshold level. device enters burst mode control on the basis of the judgment. the gate drive output switches only when vcc voltage drops below a preset level and fb input is active. otherwise the gate drive remains at off to minimize the switching loss and power consumption to the greatest extend. the frequency control also eliminates the audio noise at any loading conditions. oscillator oscillator oscillator oscillator operation operation operation operation the switching frequency is internally fixed at 65khz. no external frequency setting components are required for pcb design simplification. 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 2273. 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 fb input voltage. internal internal internal internal synchronized synchronized synchronized synchronized slope slope slope slope compensation compensation compensation compensation built-in slope compensation circuit adds slope voltage onto the current sense input voltage for pwm generation. this greatly enhances the close loop stability at ccm and prevents possible subharmonic oscillation and thus reduces the output ripple voltage. 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
WS2273 WS2273 WS2273 WS2273 8 / 9 steady, steady, steady, steady, keep keep keep keep you you you you advance advance advance advance 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 2273. including cycle-by-cycle current limiting (ocp), over load protection (olp) and over voltage clamp, vcc clamp, under voltage lockout on vcc (uvlo), otp and ovp shut down latch. at overload condition when fb input voltage exceeds power limit threshold value for more than td_pl, control circuit reacts to shut down the output power mosfet. 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.
WS2273 WS2273 WS2273 WS2273 9 / 9 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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