WS2273 2273 Current Mode PWM Controller Features General Description ■ 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 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@Winsemi Microelectronics Co., Ltd., All right reserved. WS2273 Pin Definition and Device Marking 73: WS2273 Y: Year Code (0-9) WW: Week Code (1-52) Pin Function Description Pin Name Pin Number GND 1 FB 2 Pin Type Function Description GND Ground. Feedback input pin. The PWM duty cycle is determined by voltage Feedback Input 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 VCC 5 GATE 6 Current Monitoring Power Current sense input. Power supply Gate-driven output Totem-pole gate driver output for power MOSFET. Block Diagram GND 1 Trimmed Voltage/ Current Reference Mode Select OLP FB 2 RT 3 Internal Reference Soft Driver Timer Logic Fault Management 6 Gate Inter 5V supply POR regulator UVLO 5 Vcc_OVP LEB OTP VCC 4 CS Soft Start 2/9 Steady, keep you advance WS2273 Ordering Information Package IC Marking Information Purchasing Device Name 6-Pin SOT23-6, Pb-free 73XX 2273TP（SOT23-6） Recommended Operating Condition Symbol Parameter Value Unit VCC VCC supply voltage 10~30 V RT RT resistor value 100 Kohm TA Operating temperature -20~85 ℃ Absolute Maximum Ratings Symbol Parameter Value 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. 3/9 Steady, keep you advance WS2273 Electrical Characteristics (TA=25℃，VCC=16V, if not otherwise noted) Supply Voltage (VCC) symbol parameter Test condition Min Typ Max Unit 30 V VCC_OP Operation voltage 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 VCC_Clamp VCC Zener Clamp Voltage V OVP(ON) Over voltage protection voltage 13 IVCC=10mA 30 32 34 26 28 30 CS=0.3V,FB=3V, Ramp up VCC until gate clock is off Vlatch_release Latch release voltage 5 Feedback Input Section VFB_Open VFB Open Loop Voltage 3.9 4.2 V Avcs PWM input gain ΔVfb/ΔVcs 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 0.4 mA VTH_PL Power limiting FB Threshold 3.7 V TD_PL Power limiting Debounce ZFB_IN Input Impedance Max_Duty Maximum duty cycle FB Shorted to GND 80 88 96 16 75 80 ms kΩ 85 % Current CS Section SST Soft Start time 4 ms TLEB Leading edge Blanking Time 220 ns ZCS Input impedance 40 kΩ TD_OC OCP control delay GATE with 1nF to GND 120 ns VTH_OC OCP threshold FB＝3V 0.75 V 0.9 V Vocp_clamping Oscillator Section Fosc Normal Oscillation Frequency Fosc_BM Burst mode frequency Frequency variation VCC=14V,FB=3V,CS=0.3V 60 65 70 khz 22 khz TEMP = -20 to 85℃ 1 % VCC = 12 to 25V 1 % versus ∆f_temp temp. Deviation ∆f_VCC Frequency variation versus VCC F_shuffling Shuffling Frequency 32 Hz ∆f_OSC Frequency Jittering ±4 % 4/9 Steady, keep you advance WS2273 GATE Output Section VOL Output voltage Low VCC = 14V, Io = -5mA VOH Output voltage high VCC = 14V, Io = 20mA VClamp Output clamp voltage Tr Rising time Tf Falling time 1 6 V V 12 V 175 ns 85 ns GATE with 1nF to GND， Gate 从 1~12V GATE with 1nF to GND， Gate 从 12~1V Over temperature protection IRT Output current of RT pin Votp Threshold voltage for OTP Td_OTP OTP debounce time 95 100 105 uA 0.95 1 1.05 V Cycl 16 e VRT_FL Float voltage at RT pin Vth_OVP External OVP threshold voltage 2.3 V 4 V 5/9 Steady, keep you advance WS2273 Typical Operating Characteristics 6/9 Steady, keep you advance WS2273 Function Description a period of time. Therefore reducing the switch event 2273 is a high performance current mode PWM leads to reduction on the power loss and thus saving the controller, optimized for low power AC/DC application. energy. Ultra low startup current and operating current together For the burst mode control circuit, 2273 self adjusts the with burst mode feature minimize the standby power switching mode according to the loading condition. At the consumption and improve the switching efficiency. In condition of no load or light/medium load, the FB input addition to reduce the external component count, the voltage drops below burst mode threshold level. Device internal synchronous slope compensation combines with enters Burst Mode control on the basis of the judgment. the leading-edge blanking improves system large The gate drive output switches only when VCC voltage stability subharmonic drops below a preset level and FB input is active. oscillation. 2273 also have multiform general recovery and reduces the possible Otherwise the gate drive remains at off to minimize the protection mode. The main function is described as switching loss and power consumption to the greatest below . 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 Oscillator Operation at 5uA, so that VCC could be charged up above UVLO The switching frequency is internally fixed at 65kHz. No threshold level and device starts up quickly. A large value external frequency setting components are required for startup resistor can therefore be used to minimize the PCB design simplification. 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. 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 Operating Current external RC filtering on sense input is no longer required. The operating current of 2273 is low at 1.8mA. Excellent The current limit comparator is disabled and thus cannot efficiency is achieved with low operating current together turn off the internal MOSFET during the blanking period. and extended burst mode control circuit. PWM duty cycle is determined by the current sense input voltage and the FB input voltage. Soft Start 2273 features an internal 4ms soft start to soften the Internal Synchronized Slope Compensation electrical stress occurring in the power supply during Built-in slope compensation circuit adds slope voltage startup. It is activated during the power on sequence. As onto the current sense input voltage for PWM generation. soon as VCC reaches UVLO （ OFF ）， the CS peak This greatly enhances the close loop stability at CCM voltage is gradually increaced from 0.15V to the and prevents possible subharmonic oscillation and thus maximum level. Every restart up is followed by a soft reduces the output ripple voltage. start. Gate Drive Extended Burst Mode Operation The gate drive strength which is too weak leads to over At zero load or light load, most of the power dissipation switch loss of MOSFET while too strong gate drive of the switching power supply comes from the MOSFET output compromises in the over EMI. A good tradeoff switching loss, the core loss of the transformer and the between output strength and dead time control is loss on the snubber circuit. The magnitude of power loss achieved through the design of the built-in totem pole is in proportion to the number of switching events within gate. The low standby dissipation and good EMI system 7/9 Steady, keep you advance WS2273 design is easier to achieve through this dedicated devise. Under Voltage Lockout on VCC (UVLO), OTP and OVP For MOSFET gate protection, an internal 12V clamp is shut down latch. At overload condition when FB input added at higher than expected VCC 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 Protection Controls the voltage drops below UVLO limit. It is clamped when VCC Including is higher than threshold value. The power MOSFET is Cycle-by-Cycle current limiting (OCP), Over Load shut down when VCC drops below UVLO limit and Protection (OLP) and over voltage clamp, VCC Clamp, device enters power on start-up sequence thereafter. Excellent system comprehensive stability protection is achieved of 2273. by 8/9 Steady, keep you advance 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