OB2001WKCPA

OB2001xK High Performance synchronous rectifier GENERAL DESCRIPTION FEATURES OB2001xK is a high performance and tightly integrated secondary side synchronous rectifier for switch mode power supply system. It combines a much lower voltage drop N-channel MOSFET to emulate the traditional diode rectifier at the secondary side of Flyback converter, which can reduce heat dissipation, increases output current capability and efficiency and simplify thermal design. OB2001xK can support low system output voltage down to 2V at constant current mode. It is suitable for multiple mode applications including discontinuous conduction mode and quasi-resonant mode. With its versatility and optimization, OB2001xK can be used in various switch mode power supply topologies including secondary-side control topology and primary-side control topology. From the information on the secondary side of the isolation transformer, OB2001xK generates a driving signal with dead time with respect to the primary side PWM signal to turn the integrated Nchannel SR switch on and off in proximity of the zero current transition. It is optimized for 5V output voltage. The externally adjustable minimum on time and property off time control scheme effectively avoid the ring impact induced by parasitic elements so that a reliable and noise free operation of the SR system is insured. OB2001xK is offered in SOP8 package. ■ 一 ■ ■ ■ ■ 派 ■ ■ Secondary-side synchronous rectifier optimized for 5V output system Suitable for DCM, QR operation Accurate secondary side MOSFET Vds sensing Low cost small size CC/CV mode support Up to 200kHz operation frequency Output voltage overshoot control VDD UVLO protection APPLICATIONS lt o AC/DC 5V adaptors Cell phone charger 5V Bias supply Low voltage rectification circuits ht co nf id en tia ■ ■ ■ ■ O n- Br ig TYPICAL APPLICATION ©On-Bright Electronics Confidential 1 Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier GENERAL INFORMATION Absolute Maximum Ratings Parameter Value Vin pin -0.6V to 7V VDD pin -0.6V to 7V VD pin -2.5V to 50V Note2 VS pin -0.6V to 7V RT pin -0.6V to 7V Drain pin -0.6V to BVdss Note3 Min/Max Operating -40 to 150 ℃ Junction Temperature TJ Operating Ambient -20 to 85 ℃ Temperature TA Min/Max Storage -55 to 150 ℃ Temperature Tstg Lead Temperature 260 ℃ (Soldering, 10secs) lt o 派 一 Pin Configuration The OB2001xK is offered in SOP8 package, shown as below. en tia Note1: Stresses beyond 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 under “recommended operating conditions” is not implied. Exposure to absolute maximum-rated conditions for extended periods may affect device reliability. Note2: -2.5V applies to minimum duty cycle during normal operation only. Note3: -0.6V is self-clamped Br ig ht co nf Package Dissipation Rating Package RJA(℃/W) SOP8 90 id Ordering Information Part Number Description OB2001WKCP SOP8, Halogen-free in Tube OB2001WKCPA SOP8, Halogen-free in T&R OB2001xK X Package C:SOP8 X X Package Pb-free P:Green (Halogen-free) Packing Blank:Tube A: Tape/Reel O n- High Performance Synchronous Rectifier Recommended Operating Range Symbol Parameter Min/Max VDD VDD Supply Voltage 4V to 5.5V ©On-Bright Electronics Confidential 2 Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier S en tia lt o Y:Year Code WW:Week Code(01-52) ZZZ:Lot Code C:SOP8 Package P:Halogen-free Package K:Character Code S:Internal Code(Optional) 派 YWWZZZ OB2001WCP K 一 Marking Information TERMINAL ASSIGNMENTS nf id Description This pin is connected to external n-channel MOSFET source This pin is connected to external n-channel MOSFET drain SR Mosfet drain pin. This pin is connected to secondary-side winding of transformer Ground. Power Supply System output voltage detection Minimum on time control pin. A resistor is connected from this pin to GND co I/O I I I/O P P I O O n- Br ig ht Pin Name VS VD Drain GND VDD Vin RT ©On-Bright Electronics Confidential -3- Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier O n- Br ig ht co nf id en tia lt o 派 一 BLOCK DIAGRAM ©On-Bright Electronics Confidential 4 Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier ELECTRICAL CHARACTERISTICS (TA = 25℃, VDD=5V, unless otherwise noted) Symbol Parameter Supply Voltage (VDD) Test Conditions I_VDD_operation Operation current Frequency@VD=6 5KHz,VDD=5V Frequency@VD=2 KHz,VDD=5V lt o RT Section Max Unit 一 2.0 mA 0.7 mA 4.2 V 2.8 3.0 3.2 V 2.9 3.1 3.3 V -350 mV -5 mV 100 ns 75 ns RT=25KΩ 1.9 Voltage reference at RT pin 0.95 nf Vrt 0.5 en tia SR MOSFET minimum on time id T_minimum_on 1.5 派 VDD_regulation_ Minimum VDD regulation voltage mini UVLO(ON) VDD Under Voltage Lockout Entry VDD Under Voltage Lockout Exit UVLO(OFF) (Recovery) VD Detection Section SR MOSFET turn on threshold voltage Vth_SR_act detection at VD SR MOSFET turn off threshold voltage Vth_SR_deact detection at VD Tdelay_on SR MOSFET turn-on propagation delay Tdelay_off SR MOSFET turn-off propagation delay Min Typ. Br ig ht co Overshoot Control Section System output 1st overshoot clamp control Vin_High_clamp_ trigger voltage at Vin with SR frequency 1st lower than 7.5KHz Vin_High_clamp_ System output 2nd overshoot clamp control 2nd trigger voltage at Vin System output overshoot clamp current at IVin_High_clamp Vin 1 us 1.05 V 5.65 V 6.15 V 70 mA n- SR Mosfet Section O Parameter Product OB2001WK ©On-Bright Electronics BVdss(V) MOSFET Drain-Source Breakdown Voltage Min Typ. Max 40 Rds,on(mΩ) On resistance Min Typ. Max 15 Confidential 5 Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier CHARACTERIZATION PLOTS UVLO(OFF)(V) vs Tem perature UVLO(ON)(V) vs Tem perature 3.5 3.10 2.90 2.70 2.50 3.3 3.1 2.9 一 3.30 2.7 2.5 -40 -10 20 50 80 110 140 -40 -10 50 80 110 140 Temperature(℃) VRT(V) vs Tem perature en tia 1.05 1.03 VRT(V) 20 lt o Temperature(℃) 派 UVLO(ON)(V) UVLO(OFF)(V) 3.50 1.01 0.99 0.97 -40 -10 20 50 80 110 140 O n- Br ig ht co nf Temperature(℃) id 0.95 ©On-Bright Electronics Confidential 6 Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier Operation Description Adjustable minimum on time OB2001xK offers adjustable minimum on time control. This timer can avoid effectively false turnoff due to high frequency interference caused by parasitic element at the start of secondary-side demagnetization. Tonmin=8*RT*10E(-11) 一 OB2001xK is a high performance and versatile synchronous rectifier. It can emulate the behavior of Schottky diode rectifier which directly reduces power dissipation of the traditional rectifiers and indirectly reduces primary-side loss due to compounding of efficiency gains. Adaptive minimum off time At the end of demagnetization, SR MOSFET will be turn off. The remaining current will flow through body diode again, which may result in negative voltage (about -700mV) appears at drain and SR MOSFET will turn on again. In addition, the resonance oscillation between the magnetization inductance and parasitic capacitance after demagnetization may cause negative drain voltage. These may turn on SR MOSFET by mistake. To avoid above mis-turn-on of SR MOSFET, constant minimum off time can be used to screen it. But it may disturb SR MOSFET operation. For reliable SR operation, proprietary adaptive minimum off time control is implemented in OB2001xK, which can guarantee reliable synchronous rectification operation in DCM, QR. lt o 派 Startup and under voltage lockout(UVLO) OB2001xK implements UVLO function during startup. When VDD rises above UVLO(off), the IC wakes up from under voltage lock out state and enter normal operation. When VDD drops below UVLO(on), the IC enter under voltage lock out state again and the SR gate is pulled low by 10K resistor on chip. In addition, there is a hysteresis window between UVLO(off) and UVLO(on) to make system work reliably. Br ig ht co nf id en tia Synchronization rectifier OB2001xK controls the turn-on and turn-off of synchronization rectifier MOSFET (SR MOSFET) by detection of drain-source voltage. When demagnetization of transformer starts, the secondary-side current will flow through the body diode of SR MOSFET and the voltage at the drain will drop to about -700mV. As soon as OB2001xK detects this negative voltage, the driver voltage is pulled high to turn on the SR MOSFET after very short delay time about 100nS, refer to Fig.1. After the SR MOSFET is turned on, the drain voltage of SR MOSFET begins to rise based on its Rdson and secondary-side current. The drain voltage becomes higher with demagnetization going on. When the drain voltage rises above 5mV, the driver voltage will be pulled down to ground very quickly, refer to Fig.1 O n- PCB Layout Consideration The following rules should be followed in OB2001xK PCB Layout: The Area of Power Loop: The area of the secondary current loop including the OB2001xK and the output capacitor should be as small as possible to reduce EMI radiation. And the PCB trace must be wide and short for thermal consideration. Ground Path: The VS pin should be shorted directly to the GND pin under the bottom of OB2001xK before single point connected to the negative node of the output capacitor (Pink region as shows in Fig.3). This increases the copper area at the bottom of OB2001xK for heat dissipation and reduce the impedance between VS pin and GND pin. Bypass Capacitor: The bypass capacitor on VDD should be placed as close as possible to the VDD Fig.1 SR MOSFET turn-on and turn-off timing ©On-Bright Electronics Output overshoot clamp For poor system design, there is usually output overshoot during startup and load transient. To facilitate system design, OB2001xK can detect output overshoot condition and prevent overshoot happen. When output voltage rises to meet the inner threshold, OB2001xK will open a discharge path from Vin to ground to clamp the system output voltage, so the system output overshoot can be prevented. Confidential 7 Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier 派 一 pin. And the negative node of VDD capacitor should be connected directly to the GND pin (White region as shows in Fig.3). VD pin and Drain pin: The resistor in the Fig.3 is recommended to be placed between the VD pin and the Drain pin for improving the ESD ability. The recommended value of the resistor is 10ohm with package type of 0805. No trace under this resistor is required (Green region as shows in Fig.3). en tia lt o Fig.3 Recommend PCB Layout of OB2001xK O n- Br ig ht co nf id Fig.2 Proper Loop at the Secondary Side of the Flyback with OB2001xK ©On-Bright Electronics Confidential 8 Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier Br ig ht co nf id en tia lt o 派 一 PACKAGE MECHANICAL DATA O n- Symbol A A1 A2 b c D E E1 e L θ ©On-Bright Electronics Dimensions In Millimeters Min Max 1.350 1.750 0.050 0.250 1.250 1.650 0.310 0.510 0.170 0.250 4.700 5.150 3.800 4.000 5.800 6.200 1.270 (BSC) 0.400 1.270 0º 8º Confidential 9 Dimensions In Inches Min Max 0.053 0.069 0.002 0.010 0.049 0.065 0.012 0.020 0.006 0.010 0.185 0.203 0.150 0.157 0.228 0.244 0.05 (BSC) 0.016 0.050 0º 8º Datasheet OB_DOC_DS_2001xKA1 OB2001xK W High Performance Synchronous Rectifier IMPORTANT NOTICE 一 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. lt o 派 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 application 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. en tia 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 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 10 Datasheet OB_DOC_DS_2001xKA1