general description HT2273 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, ht227 3 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. HT2273 offers comprehensive protection coverage with automatic self-recovery feature, including cycle by cycle over current pr otection (ocp), over load protection (olp),vcc cl amp, 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 fr equency jittering at the totem-pole-gate-drive output. the tone energy at below 20khz is minimi zed in the design and audio noise is eliminated during operation. the HT2273 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. HT2273 is available in sot23-6 package. 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 switch 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 HT2273 1 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
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 application circuit pin definition and device marking ordering information package ic marking information purchasing device name 6-pin sot23-6, pb-free 73xx HT2273tp sot23-6 73: HT2273 y: year code ww: week code (1-52) HT2273 2 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
pin function description pin name pin number pin type function description gnd 1 gnd ground. fb 2 feedback input feedback input pin. the pw m duty cycle is determined by voltage level into this pin and the current-sense signal at pin 4. the internal protec tion circuit will automatically shutdown when the fb voltage level exceeds a preset threshold voltage. rt 3 otp setting dual function pi n. either connected through a ntc resistor to ground for over temperature shut down/latch control or connected th rough 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 diagram HT2273 3 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
absolute maximum ratings symbol parameter value unit vcc dc supply voltage 30 v v fb fb input voltage -0.3~7 v v cs cs input voltage -0.3~7 v v rt rt input voltage -0.3~7 v t j operating junction temperature -20~150 t stg storage temperature -40~150 v cv vcc clamp voltage 26 v i cc vcc dc clamp current 10 ma note : stresses above those listed under absolute maximum ratings may cause permanent da mage 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 implie d. exposure to absolute maximum-rated conditions for extended periods may affect device reliability. recommended operating condition symbol parameter value unit vcc vcc supply voltage 10~30 v rt rt resistor value 100 kohm t a operating temperature -20~85 electrical characteristics (t a =25 vcc=16v, if not otherwise noted) supply voltage (vcc) symbol parameter test condition min typ. max 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 v fb =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 HT2273 4 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
vlatch_release latch release voltage 5 feedback input section v fb _open v fb 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 v th _pl power limiting fb threshold 3.7 v t d _pl power limiting debounce 80 88 96 ms z fb _in input impedance 16 k ? max_duty maximum duty cycle 75 80 85 % current cs section sst soft start time 4 ms tleb leading edge blanking time 220 ns z cs input impedance 40 k ? t d _oc ocp control delay gate with 1nf to gnd 120 ns v th _oc ocp threshold fb 3v 0.75 v vocp_clamping 0.9 v oscillator 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 % gate output 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 HT2273 5 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
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 temperature 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 cycle vrt_fl float voltage at rt pin 2.3 v vth_ovp external ovp threshold voltage 4 v HT2273 6 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
typical operating characteristics HT2273 7 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
function description HT2273 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 impr ove the switching efficiency. in addition to reduce the external component count, the internal synchronous slope compensation combines with the leading-edge blanking im proves system large stability and reduces t he possible subharmonic oscillation. HT2273 also have multiform general recovery protection mode. the main function is described as below: startup current and startup control startup current of HT2273 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 des ign 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 current the operating current of HT2273 is low at 1.8ma. excellent efficiency is achieved with low operating current toget her and extended burst mode control circuit. soft start HT2273 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 sequenc e. 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 burst mode operation at zero load or light load, most of the power dissipation of the switching power supply comes from the mosfet switch ing 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 cont rol circuit, HT2273 self adjusts the switching mode according to the loading condition. at t he 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 sw itches 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 operation the switching frequency is internally fixed at 65khz. no external frequency setting HT2273 8 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
components are required for pcb design simplification. current sensing and leading edge blanking cycle-by-cycle current limiting is offered in HT2273. 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 filterin g 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 t he current sense input voltage and the fb input voltage. internal synchronized slope compensation built-in slope compensat ion 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 drive the gate drive strength wh ich 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 to tem 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 controls excellent system stability is achieved by the comprehensive protection of HT2273. 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 circui t 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. HT2273 9 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
package information sot23-6 package outline dimensions symbol dimensions in milimeters dimensions in inches 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 ? HT2273 10 of 10 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
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