OB2004AZCPA-C

OB2004Ax High Performance Synchronous Rectifier GENERAL DESCRIPTION FEATURES OB2004Ax 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. It can support wide range of system output voltage 3V~12V. It is suitable for multiple mode applications including discontinuous conduction mode (DCM), quasi-resonant mode (QR) and continuous conduction mode (CCM). Specially for CCM, to guarantee system reliability, innovative property prediction algorithm is used in SR turn-off control. In addition, to balance reliability and efficiency, OB2004Ax generates a driving signal with optimized dead time with respect to the primary side PWM signal from the information on the secondary side of the isolation transformer with the help of innovative property dead time control algorithm. The innovative property off time control effectively avoid the ring impact induced by parasitic elements so that a reliable and noise free operation of the SR system is insured. OB2004Ax is offered in SOP8 package. ■ ■ ■ p lc om ■ sa ■ ■ ■ ■ Secondary-side synchronous rectifier for 3V~12V output system Suitable for DCM, QR and CCM operation Prediction algorithm for CCM Internal Power MOSFET Accurate secondary side MOSFET Vds sensing SR turn on/off dead-time control for high efficiency and low thermal with immunity of interference Adaptive off time control effectively avoid the ring impact induced by parasitic elements VDD UVLO protection APPLICATIONS to AC/DC 3V~12V chargers/adaptors Low voltage rectification circuits on fid en tia l ■ ■ O nB rig ht c TYPICAL APPLICATION ©On-Bright Electronics Confidential 1 Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier GENERAL INFORMATION Absolute Maximum Ratings Parameter Value Vin pin -0.6V to 24V VDD pin -0.6V to 8V Drain pin -2.5V to 60V 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) sa lc om p Pin Configuration The OB2004Ax is offered in SOP8 package, shown as below. 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. en tia l Output Power Table Part Number OB2004AWCP OB2004AZCP rig ht c Recommended Operating Range Symbol Parameter Min/Max VDD VDD Supply Voltage 4.2V to 5V OB2004Ax Output X Package C:SOP8 X X Green Package P: Green (Halogen-free) Packing Blank:Tube A: Tape/Reel O nB High Performance Synchronous Rectifier Maximum Current 2A 3A Note: Maximum practical continuous power in a charger designed with sufficient drain pattern as a heat sink, at 40℃ ambient. on fid Package Dissipation Rating Package RJA(℃/W) SOP8 85 to Ordering Information Part Number Description OB2004AZCP SOP8, Halogen-free in Tube OB2004AZCPA SOP8, Halogen-free in T&R OB2004AWCP SOP8, Halogen-free in Tube OB2004AWCPA SOP8, Halogen-free in T&R ©On-Bright Electronics Confidential 2 Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier YWWZZZ OB2004WCP A S Y:Year Code WW:Week Code(01-52) ZZZ:Lot Code C:SOP8 Package P:Halogen-free Package A:Character Code S:Internal Code(Optional) Y:Year Code WW:Week Code(01-52) ZZZ:Lot Code C:SOP8 Package P:Halogen-free Package A:Character Code S:Internal Code(Optional) to sa lc om YWWZZZ OB2004ZCP A S TERMINAL ASSIGNMENTS I Description Ground Power Supply System output voltage detection SR Mosfet drain pin. This pin is connected to secondary-side winding of transformer en tia l I/O P P I O nB rig ht c on fid Pin Name GND-(1,2pin) VDD-(3pin) Vin-(4pin) Drain(5,6,7,8pin) p Marking Information ©On-Bright Electronics Confidential -3- Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier BLOCK DIAGRAM VDD Vin p Drain lc om Regulator1 Bias System Output Detection PG AVDD UVLO sa Regulator2 to AVDD 200mV Drain Min on time R SR en tia l HV Switch Logic Control Driver S on fid VS Ring Detection ht c Demag_Det Prdiction O nB rig GND ©On-Bright Electronics Confidential 4 Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier ELECTRICAL CHARACTERISTICS (TA = 25℃, VDD=5V, unless otherwise noted) Symbol Parameter Test Conditions Min Typ. Max Unit Supply Voltage (VDD) VDD_regulation_min VDD regulation voltage VDD_regulation_max VDD regulation voltage VDD Under Voltage Lockout Entry VDD Under Voltage Lockout UVLO(ON) Exit (Recovery) VDrain Detection Section SR MOSFET turn on threshold Vth_SR_act voltage detection at VDrain Adjustable SR MOSFET turn Vth_SR_deact off threshold voltage detection at VDrain SR MOSFET fast path turn-on propagation delay Tdelay_on SR MOSFET slow path turn-on propagation delay SR MOSFET turn-off Tdelay_off propagation delay Voltage level at Vin when SR is Vin_sr_disable disable CCM Prediction Section en tia l p mA 0.8 mA 4.2 V 5 V 3.0 V 2.4 V -150 -200 -250 mV on fid ht c Tsr_on_max 1.6 -1 mV 70 ns 200 ns 75 ns 1.9 2.1 2.3 V No sub-harmonic condition 63 66 69 % With sub-harmonic condition 12 15 18 % 35 40 45 us rig Prediction ratio 0.6 to UVLO(OFF) Rpre 1.2 lc om Operation current sa I_VDD_operation Frequency@VDrain=65KHz,V DD=5V, 1nF Cap load at GATE. Frequency@VDrain=2KHz, VDD=5V, No load at GATE. Frequency@VDrain=50KHz, Duty=25%, High level @VDrain=20V Vin5.5V Maximum SR turn-on time nB Dead-time Control Section Maximum SR turn-off dead time 0.8 us O Tdt_off_max ©On-Bright Electronics Confidential 5 Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier Product BVdss(V) MOSFET Drain-Source Breakdown Voltage Min Typ. Max Rds,on(mΩ) On resistance Min Typ. Max OB2004AZCP 60 8 OB2004AWCP 60 16 O nB rig ht c on fid en tia l to sa CHARACTERIZATION PLOTS lc om Note1：Suggesting primary side controller operating at 65kHz frequency p Parameter ©On-Bright Electronics Confidential 6 Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier Operation Description p OB2004Ax 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. sa lc om Startup and under voltage lockout (UVLO) Whether OB2004Ax can operate normally or not depends on UVLO function implemented on chip and system output voltage. When power system is plugged in, VDD cap is charged from transformer secondary winding. When VDD rises above UVLO(off), the IC wakes up from under voltage lock out state and monitors the system output voltage through Vin pin. OB2004Ax will output SR gate based on correct timing after VDD rises above 3.0V(typical). Refer to the following timing diagram. to Fig.3 System output SCP timing diagram en tia l Additionally, there is a pull down on-chip 15Kohm resistor to avoid the misconducting by VDrain pulse coupling. Besides, a hysteresis window between UVLO(off) and UVLO(on) makes system work reliably. Synchronization rectifier OB2004Ax controls the turn-on and turn-off of synchronization rectifier MOSFET (SR MOSFET) by detection of drain-source voltage and prediction control. 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 below -200mV (typical). As soon as OB2004Ax detects this negative voltage, the driver voltage is pulled high to turn on the SR MOSFET after variable delay time depending on input line voltage and loading condition, refer to Fig.4.This variable delay time can improve system immunity to noise． 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 1mV, the driver voltage will be pulled down to ground very quickly, refer to Fig.4 O nB rig ht c on fid Fig.1 System start up timing diagram With enough high Vin, OB2004Ax would be powered from VDD and system output (Vin), which can lead to better system efficiency. When VDD drops below UVLO(on),SR would be disable. Refer to the following timing diagram. For system reliability, the SR gate would be pulled low when VDD is lower than 2.4V (typical). Refer to the following timing diagram. Fig.2 System shut down timing diagram ©On-Bright Electronics Confidential 7 Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier primary side to be 0.8uS in stable CCM operation to further improve the efficiency while ensure the safe operation. Primary-side PWM p Vp lc om VDrain Tdemag(n) Tdemag(n+1) Demag sa Prediction Tsr_on(n) SR Tsr_on(n+1) Tsr_on(n+1) = Tdemag(n) * 66% Fig.5 Prediction in stable CCM to Fig.4 SR MOSFET turn-on and turn-off timing on fid en tia l Prediction control in CCM When system works in CCM mode, drain voltage can not rise above -1mV when primary side turns on. In this case the property prediction algorithm implemented in OB2004Ax turns off the SR. OB2004Ax would detect the demagnetization time of current cycle and use this information to turn off SR in next cycle. For stable CCM, there is little variation between consecutive demagnetization phase, so the next cycle SR can be turn off predictively with pre-set prediction ratio, such as 66%. This means the next SR turn-on would last 66% of current demagnetization time before turn off. However when sub-harmonic switching happens, there is risk of short-circuit of transformer if both primary side and secondary side switch controllers are in turn-on phase. To avoid this risk, OB2004Ax would detect the primary side turn on time. If the primary side turn on time of current cycle is 500ns (typical) longer than the previous cycle, the pre-set prediction ratio would be changed from 66% to 15% so that the SR turn-on time is significantly reduced to avoid the risk of short-circuit of transformer. Fig.5 and Fig.6 illustrates the control scheme. In the next consecutive cycles, the SR on-time will be gradually increased that improve the efficiency. Fig.6 Prediction in CCM with sub-harmonic O nB rig ht c Dead time control For efficiency and thermal issue, the demagnetization current flowing through SR MOSFET body diode after SR turn off should be as small as possible, i.e the dead time between SR turn off and demagnetization ending is as short as possible. But when SR MOSFET Rdson is too small or interference riding on Vds, SR maybe turn off prematurely. In this case, an adaptive dead time control algorithm used in OB2004Ax can correct the dead time to 0.8uS (typical) for good efficiency and thermal performance. In addition, a adaptive dead time control is implemented (described in next section). It regulates the time period (dead time) between the SR tune off instance and turn on instance of the ©On-Bright Electronics Confidential 8 Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier PACKAGE MECHANICAL DATA ht c on fid en tia l to sa lc om p SOP8 PACKAGE OUTLINE DIMENSIONS Symbol Dimensions In Inches Min Max Min Max 1.350 1.750 0.053 0.069 A1 0.050 0.250 0.002 0.010 A2 1.250 1.650 0.049 0.065 b 0.310 0.510 0.012 0.020 c 0.100 0.250 0.004 0.010 D 4.700 5.150 0.185 0.203 E 3.800 4.000 0.150 0.157 E1 5.800 6.200 0.228 0.244 nB rig A O Dimensions In Millimeters e 1.270 (BSC) 0.050 (BSC) L 0.400 1.270 0.016 0.050 θ 0º 8º 0º 8º ©On-Bright Electronics Confidential 9 Preliminary Datasheet OB_DOC_DS_2004Ax03 OB2004Ax W High Performance Synchronous Rectifier IMPORTANT NOTICE p 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. sa lc om 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 l to 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 nB rig ht c on fid 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 Preliminary Datasheet OB_DOC_DS_2004Ax03