WS2273

WS2273 2273 Current Mode PWM Controller 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 General Description 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. 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 Rev.A Oct.2011 Copyright@W ins emi Microelectronics Co., Ltd., All right reserved. WS2273 WS2273 Pin Definition and Device Marking 73: WS2273 Y: Year Code (0-9) WW: Week Code (1-52) Pin Function Description Pin Name GND FB 1 2 Feedback Input Pin Number Pin Type GND Ground. Function Description 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. 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. RT 3 OTP Setting CS VCC GATE 4 5 6 Current Monitoring Power Gate-driven output Current sense input. Power supply Totem-pole gate driver output for power MOSFET. Block Diagram Trimmed Voltage/ Current Reference GND 1 Internal Reference S of t Driver 6 Gate FB 2 Mode S el e c t OLP Inter 5V supply Timer Logic Fault Management regulator POR UVLO 5 VCC Vcc_OVP RT 3 OTP LEB Soft Start 4CS 2/9 Steady, keep you advance WS2273 WS2273 Ordering Information Package 6-Pin SOT23-6, Pb-free IC Marking Information 73XX Purchasing Device Name 2273TP（SOT23-6） Recommended Operating Condition Symbol VCC RT TA Parameter VCC supply voltage RT resistor value Operating temperature Value 10~30 100 -20~85 Unit V Kohm ℃ Absolute Maximum Ratings Symbol VCC VFB VCS VRT TJ TSTG VCV ICC Parameter DC supply voltage FB input voltage CS input voltage RT input voltage Operating junction temperature Storage temperature VCC clamp voltage VCC DC clamp current Value 30 -0.3~7 -0.3~7 -0.3~7 -20~150 -40~150 26 10 Unit V V V V ℃ ℃ V 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. 3/9 Steady, keep you advance WS2273 WS2273 Electrical Characteristics (TA=25℃，VCC=16V, if not otherwise noted) Supply Voltage (VCC) symbol VCC_OP UVLO_ON UVLO_OFF I_VCC_ST I_VCC_OP Vpull_up VCC_Clamp OVP(ON) Vlatch_release parameter Operation voltage Turn on threshold Voltage Turn-off threshold Voltage Start up current Operation Current Pull-up PMOS active VCC Zener Clamp Voltage Over voltage protection voltage VCC until gate clock is off Latch release voltage 5 IVCC=10mA CS=0.3V,FB=3V, Ramp up 26 28 30 30 VCC=13V VFB=3V 6 12.5 7 13.5 5 1.8 13 32 34 V Test condition Min Typ Max 30 8 14.5 20 2.5 Unit V V V uA mA Feedback Input Section VFB_Open Avcs Vref_green Vref_burst_H Vref_burst_L IFB_Short VTH_PL TD_PL ZFB_IN Max_Duty VFB Open Loop Voltage PWM input gain ΔVfb/ΔVcs The threshold enter green mode The threshold exit burst mode The threshold enter burst mode FB Pin Short Current Power limiting FB Threshold Power limiting Debounce Input Impedance Maximum duty cycle 75 80 FB Shorted to GND 3.9 4.2 2 2.1 1.3 1.2 0.4 3.7 88 16 80 85 96 V V/V V V V mA V ms kΩ % Current CS Section SST TLEB ZCS TD_OC VTH_OC Vocp_clamping Oscillator Section Fosc Fosc_BM ∆f_temp temp. Deviation ∆f_VCC F_shuffling ∆f_OSC Frequency variation versus VCC Shuffling Frequency Frequency Jittering VCC = 12 to 25V 1 32 ±4 % Hz % 4/9 Normal Oscillation Frequency Burst mode frequency Frequency variation versus TEMP = -20 to 85℃ VCC=14V,FB=3V,CS=0.3V 60 65 22 1 70 khz khz % Soft Start time Leading edge Blanking Time Input impedance OCP control delay OCP threshold GATE with 1nF to GND FB＝3V 4 220 40 120 0.75 0.9 ms ns kΩ ns V V Steady, keep you advance WS2273 WS2273 GATE Output Section VOL VOH VClamp Tr Output voltage Low Output voltage high Output clamp voltage GATE with 1nF to GND， Rising time Gate 从 1~12V GATE with 1nF to GND， Tf Falling time Gate 从 12~1V 85 ns 175 ns VCC = 14V, Io = -5mA VCC = 14V, Io = 20mA 6 12 1 V V V Over temperature protection IRT Votp Td_OTP VRT_FL Vth_OVP Output current of RT pin Threshold voltage for OTP OTP debounce time Float voltage at RT pin External OVP threshold voltage 95 0.95 100 1 16 e 2.3 4 V V 105 1.05 uA V Cycl 5/9 Steady, keep you advance WS2273 WS2273 Typical Operating Characteristics 6/9 Steady, keep you advance WS2273 WS2273 Function 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 . 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. Startup Current and Startup 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 Ω , 1/8 W could be used together with a VCC capacitor to provide a fast startup and low power dissipation solution. Oscillator Operation The switching frequency is internally fixed at 65kHz. No external frequency setting components are required for PCB design simplification. Current Sensing and Leading Edge 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. Operating 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 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. Internal Synchronized Slope 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 Drive Extended Burst Mode 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 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 7/9 Steady, keep you advance WS2273 WS2273 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. 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 is of achieved 2273. by the 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. Protection Controls Excellent system stability comprehensive protection Including Cycle-by-Cycle current limiting (OCP), Over Load Protection (OLP) and over voltage clamp, VCC Clamp, 8/9 Steady, keep you advance WS2273 WS2273 SOT23-6 Package Outline Dimensions Symbol A A1 A2 b c D E E1 e e1 L θ Dimensions In Milimeters Min Max 1.000 1.300 0.000 0.150 1.000 1.200 0.300 0.500 0.100 0.200 2.800 3.020 1.500 1.700 2.600 3.000 0.950(BSC) 1.800 2.000 0.300 0.600 0° 8° Dimensions In Inches Min Max 0.039 0.051 0.000 0.006 0.039 0.047 0.012 0.020 0.004 0.008 0.110 0.119 0.059 0.067 0.102 0.118 0.037(BSC) 0.071 0.079 0.012 0.024 0° 8° 9/9 Steady, keep you advance