OB2338AP

OB2338 High Performance Current Mode PWM Power Switch GENERAL DESCRIPTION FEATURES OB2338 combines a dedicated current mode PWM controller with a high voltage power MOSFET. It is optimized for high performance, low standby power, and cost effective off-line flyback converter applications in sub 27W range. OB2338 offers complete protection coverage with automatic self-recovery feature including Cycleby-Cycle current limiting (OCP), over load protection (OLP), over temperature protection (OTP), over voltage protection and VDD under voltage lockout (UVLO). Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique together with soft switching control at the totem pole gate drive output. The tone energy at below 20KHZ is minimized in the design and audio noise is eliminated during operation. OB2338 is offered in DIP8 package. ■ 达 誉 汇 lt o ht co nf id en tia APPLICATIONS Offline AC/DC flyback converter for ■ AC/DC adapter ■ PDA power supplies ■ Digital Cameras and Camcorder Adapter ■ VCR, SVR, STB, DVD&DVCD Player SMPS ■ Set-Top Box Power ■ Auxiliary Power Supply for PC and Server ■ Open-frame SMPS Level 5 compliance with < 100mW standby power at universal AC input ■ Power on soft start reducing MOSFET Vds stress ■ Frequency shuffling for EMI ■ Extended burst mode control for improved efficiency and minimum standby power design ■ Audio noise free operation ■ Fixed 55KHZ (typical) switching frequency ■ Internal synchronized slope compensation ■ Low VDD startup current and low operating current ■ Leading edge blanking on current sense input ■ Comprehensive protection coverage o VDD under voltage lockout with hysteresis (UVLO) o Over temperature protection (OTP) with auto- recovery o On-Bright proprietary line input compensated o Cycle-by-Cycle over-current threshold setting for constant output power limiting over universal input voltage range. o Accurate Overload protection (OLP). o Over voltage protection(OVP) o Secondary Rectifier Short Protection O n- Br ig TYPICAL APPLICATION Output Power Table Product 230VAC±15% Open Frame1 27W 85-265VAC Open Frame1 16W OB2338 Notes: 1. Maximum practical continuous power in an open frame design with sufficient drain pattern as a heat sink, at 50℃ ambient. Higher output power is possible with extra added heat sink or air circulation to reduce thermal resistance. ©On-Bright Electronics Confidential -1- Datasheet OB_DOC_DS_2338A0 OB2338 High Performance Current Mode PWM Power Switch GENERAL INFORMATION Pin Configuration The OB2338 is offered in DIP8 package as shown below. Package Dissipation Rating Package RJA (℃/W) DIP8 75 Note: Drain Pin Connected to 100mm2 PCB copper clad. 汇 誉 达 Absolute Maximum Ratings Parameter Value Drain Voltage (off state) -0.3V to BVdss VDD Voltage -0.3V to 30 V VDD-G Input Voltage -0.3V to 30 V FB Input Voltage -0.3 to 7V Sense Input Voltage -0.3 to 7V Min/Max Operating Junction -40 to 150℃ Temperature TJ Min/Max Storage -55 to 150℃ Temperature Tstg Lead Temperature 260℃ (Soldering, 10secs) Note: Stresses beyond those listed under “absolute lt o 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 under “recommended operating conditions” is not implied. Exposure to absolute maximum-rated conditions for extended periods may affect device reliability. en tia Ordering Information Part Number Description OB2338AP DIP8, Pb-free X X co nf id OB2338 Package ht Current Mode PWM Power Switch P : Pb-free O n- Br ig A:DIP8 Package Pb-free Marking Information ©On-Bright Electronics Confidential -2- Datasheet OB_DOC_DS_2338A0 OB2338 High Performance Current Mode PWM Power Switch TERMINAL ASSIGNMENTS Pin Name GND I/O P FB I VDD-G SENSE VDD P I P Drain O Description Ground Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and the current-sense signal at Pin 4. Internal Gate Driver Power Supply Current sense input IC DC power supply Input HV MOSFET Drain Pin. The Drain pin is connected to the primary lead of the transformer BLOCK DIAGRAM 誉 达 VDD_G 2 Soft Driver lt o VDD 3 汇 Current Reference OTP Q S OCP Extended id LDO OSC nf Burst mode co POR SENSE 4 Slope compensation ht UVLO Power MOSFET Soft Start tia R en Internal supply Drain 5/6 LEB Vth ig CPL Br Internal supply O n- OVP Burst mode PWM Comparator Debounce R OLP FB 1 R 7/8 GND ©On-Bright Electronics Confidential -3- Datasheet OB_DOC_DS_2338A0 OB2338 High Performance Current Mode PWM Power Switch ELECTRICAL CHARACTERISTICS Min Typ Max Unit 5 20 uA 1.6 mA 7.0 8.0 9.0 V 15.2 16.2 17.2 V 27.5 29 30.5 V 4.9 5.5 6.1 V 0.35 mA 0.8 V 4.6 V 50 mSec 15.7 Kohm 4 ms 270 ns 40 Kohm 80 nSec O n- Br ig ht co nf id en tia lt o 汇 誉 达 (TA = 25℃, VDD=16V, unless otherwise noted) Symbol Parameter Test Conditions Supply Voltage (VDD) VDD=11V,Measure Istartup VDD Start up Current Leakage current into VDD I_VDD_Operation Operation Current VFB=3V VDD Under Voltage UVLO(ON) Lockout Enter VDD Under Voltage UVLO(OFF) Lockout Exit (Recovery) Over voltage protection CS=0V,FB=3V Ramp up OVP(ON) voltage VDD until gate clock is off Feedback Input Section(FB Pin) VFB_Open VFB Open Loop Voltage FB pin short circuit Short FB pin to GND and IFB_Short current measure current Zero Duty Cycle FB VTH_0D Threshold Voltage Power Limiting FB VTH_PL Threshold Voltage Power limiting Debounce TD_PL Time ZFB_IN Input Impedance Current Sense Input(Sense Pin) Soft start time Leading edge blanking T_blanking time ZSENSE_IN Input Impedance From Over Current Occurs Over Current Detection TD_OC till the gate driver output and Control Delay start to turn off Internal Current Limiting VTH_OC FB=3.3V Threshold Voltage Oscillator Normal Oscillation FOSC Frequency Frequency Temperature △f_Temp Stability Frequency Voltage △f_VDD Stability Maximum duty D_max FB=3.3V, CS =0V cycle Burst Mode Base F_Burst Frequency Mosfet Section MOSFET Drain-Source BVdss Breakdown Voltage Static Drain to Source On Rdson Resistance Frequency Shuffling Frequency Modulation ∆f_OSC range /Base frequency Over temperature protection Over temperature protection trip point ©On-Bright Electronics Confidential -4- 0.72 0.77 0.82 V 50 55 60 KHZ 65 5 % 5 % 75 85 22 % KHZ 600 V 4.4 -4 150 5.5 Ώ 4 % ℃ Datasheet OB_DOC_DS_2338A0 OB2338 High Performance Current Mode PWM Power Switch CHARACTERIZATION PLOTS (The characteristic graphs are normalized at Ta=25℃) UVLO(ON) vs Temperature UVLO(OFF) vs Temperature 20 UVLO(OFF) (V) UVLO(ON)(V) 10 9 8 7 18 16 14 12 6 10 -40 -10 20 50 80 -40 110 140 -10 80 110 140 达 誉 I_startup vs Temperature VDD vs Iop_n(uA) 汇 5 1000 4 tia 2 Iop_n(uA) lt o 800 3 en 1 0 20 50 80 110 200 0 140 0 nf -10 400 Duty vs Vth_oc ig 0.9 0.85 Fosc(KHz) 0.95 16 20 24 28 60 O n- 1 12 Fosc vs Temperature Br 1.05 8 VDD(V) ht Temperature(℃ ) 4 co -40 600 id I_startup(uA) 50 Temperature(℃ ) Temperature(℃ ) Vth_oc(V) 20 0.8 45 30 15 0 0.75 0 10 20 30 40 50 60 -40 70 -10 20 50 80 110 140 Temperature(℃ ) Duty(%) Rds(on) VS Temperature(℃ ) R ds (on) 10 8 6 4 25 50 75 100 125 150 Temperature(℃ ) ©On-Bright Electronics Confidential -5- Datasheet OB_DOC_DS_2338A0 OB2338 High Performance Current Mode PWM Power Switch OPERATION DESCRIPTION The OB2338 is a low power off-line SMPS Switcher optimized for off-line flyback converter applications in sub 27W power range. The ‘Extended burst mode’ control greatly reduces the standby power consumption and helps the design easily to meet the international power conservation requirements. frequency reduces at light/no load condition to improve the conversion efficiency. At light load or no load condition, the FB input drops below burst mode threshold level and device enters Burst Mode control. The gate drive output switches only when VDD voltage drops below a preset level and FB input is active to output an on state. Otherwise the gate drive remains at off state to minimize the switching loss and reduces the standby power consumption to the greatest extend. The switching frequency control also eliminates the audio noise at any loading conditions.  Startup Current and Start up Control Startup current of OB2338 is designed to be very low so that VDD 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 yet achieve a reliable startup in application. For AC/DC adapter with universal input range design, a 2 MΩ, 1/8 W startup resistor could be used together with a VDD capacitor to provide a fast startup and yet low power dissipation design solution. 汇 誉 达  Oscillator Operation The switching frequency of OB2338 is internally fixed at 55KHZ. No external frequency setting components are required for PCB design simplification. lt o  Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2338 current mode PWM control. The switch current is detected by a sense resistor into the sense pin. An internal leading edge blanking circuit chops off the sensed voltage spike at initial internal power MOSFET on state due to snubber diode reverse recovery and surge gate current of internal power MOSFET so that the external RC filtering on sense input is no longer needed. The current limiting comparator is disabled and cannot turn off the internal power MOSFET during the blanking period. The PWM duty cycle is determined by the current sense input voltage and the FB input voltage. id en tia  Operating Current The Operating current of OB2338 is low at 1.6mA (typical). Good efficiency is achieved with OB2338 low operating current together with the ‘Extended burst mode’ control features. O n- Br ig ht co nf  Soft Start OB2338 features an internal 4ms (typical) 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 VDD reaches UVLO(OFF), the peak current is gradually increased from nearly zero to the maximum level of 0.77V. Every restart up is followed by a soft start.  Internal Synchronized Slope Compensation Built-in slope compensation circuit adds voltage ramp onto the current sense input voltage for PWM generation. This greatly improves the close loop stability at CCM and prevents the subharmonic oscillation and thus reduces the output ripple voltage.  Frequency shuffling for EMI improvement The frequency Shuffling (switching frequency modulation) is implemented in OB2338. The oscillation frequency is modulated so that the tone energy is spread out. The spread spectrum minimizes the conduction band EMI and therefore eases the system design.  Driver The internal power MOSFET in OB2338 is driven by a dedicated gate driver for power switch control. Too weak the gate drive strength results in higher conduction and switch loss of MOSFET while too strong gate drive results in the compromise of EMI.  Extended Burst Mode Operation At light load or zero load condition, most of the power dissipation in a switching mode power supply is from switching loss on the MOSFET, the core loss of the transformer and the loss on the snubber circuit. The magnitude of power loss is in proportion to the switching frequency. Lower switching frequency leads to the reduction on the power loss and thus conserves the energy. The switching frequency is internally adjusted at no load or light load condition. The switch ©On-Bright Electronics A good tradeoff is achieved through the built-in totem pole gate design with right output strength and dead time control. The low idle loss and good EMI system design is easier to achieve with this dedicated control scheme. Confidential 6 Datasheet OB_DOC_DS_2338A0 OB2338 High Performance Current Mode PWM Power Switch In addition to the gate drive control scheme mentioned, the gate drive strength can also be adjusted externally by a resistor connected between VDD and VDDG, the falling edge of the Drain output can be well controlled. It provides great flexibility for system EMI design. shutdowns the power MOSFET when an Over Temperature condition is detected or the sense pin is opened VDD is supplied by transformer auxiliary winding output. When VDD voltage exceeds the internal OVP threshold voltage (29V, typical) due to abnormal conditions, The power MOSFET is shut down until VDD drops below 8V (typical) , and device enters power on restart-up sequence thereafter.  Protection Controls Good power supply system reliability is achieved with its rich protection features including Cycle-byCycle current limiting (OCP), Over Load Protection (OLP), over voltage protection and Under Voltage Lockout on VDD (UVLO). When the secondary rectifier is shorted, the transformer acts like a leakage inductance. Meanwhile, the current spike is extremely high. During high line input, the current in power MOSFET is too high to wait for OLP delay time. To offer reliable design, OB2338 shut down the switcher and enter into auto-recovery mode in this case. 誉 达 With On-Bright Proprietary technology, the OCP is line voltage compensated to achieve constant output power limit over the universal input voltage range. O n- Br ig ht co nf id en tia lt o 汇 At overload condition when FB input voltage exceeds power limit threshold value for more than TD_PL, control circuit reacts to shut down the switcher. Switcher restarts when VDD voltage drops below UVLO limit. Similarly, control circuit ©On-Bright Electronics Confidential -7- Datasheet OB_DOC_DS_2338A0 OB2338 High Performance Current Mode PWM Power Switch PACKAGE MECHANICAL DATA A A1 A2 B B1 C D E E1 e L E2 Dimensions In Millimeters Min Max 3.710 5.334 0.381 2.921 4.953 0.350 0.650 1.524 (BSC) 0.200 0.360 9.000 10.160 6.096 7.112 7.320 8.255 2.540 (BSC) 2.921 3.810 7.620 10.920 O n- Symbol Br ig ht co nf id en tia lt o 汇 誉 达 8-Pin Plastic DIP ©On-Bright Electronics Confidential -8- Dimensions In Inches Min Max 0.146 0.210 0.015 0.115 0.195 0.014 0.026 0.06 (BSC) 0.008 0.014 0.354 0.400 0.240 0.280 0.288 0.325 0.1 (BSC) 0.115 0.150 0.300 0.430 Datasheet OB_DOC_DS_2338A0 OB2338 High Performance Current Mode PWM Power Switch IMPORTANT NOTICE RIGHT TO MAKE CHANGES On-Bright Electronics Corp. reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 誉 达 WARRANTY INFORMATION On-Bright Electronics Corp. warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with its standard warranty. Testing and other quality control techniques are used to the extent it deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. On-Bright Electronics Corp. assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using On-Bright’s components, data sheet and application notes. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. tia lt o 汇 LIFE SUPPORT On-Bright Electronics Corp.’s products are not designed to be used as components in devices intended to support or sustain human life. On-bright Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in medical applications. O n- Br ig ht co nf id en MILITARY On-Bright Electronics Corp.’s products are not designed for use in military applications. On-Bright Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in military applications. ©On-Bright Electronics Confidential -9- Datasheet OB_DOC_DS_2338A0