OB2502PCPA

OB2502P High Precision CC/CV Primary-Side Power Switch FEATURES OB2502P is a high performance offline PSR power switch for low power AC/DC charger and adapter applications. It operates in primary-side sensing and regulation. Consequently, opto-coupler and TL431 could be eliminated. Proprietary Constant Voltage (CV) and Constant Current (CC) control is integrated as shown in the figure below. In CC control, the current and output power setting can be adjusted externally by the sense resistor Rs at CS pin. In CV control, multi-mode operations are utilized to achieve high performance and high efficiency. In addition, good load regulation is achieved by the built-in cable drop compensation. Device operates in PFM in CC mode at large load condition and it operates in PWM with frequency reduction at light/medium load. The chip consumes very low operation current. It achieves less than 75mW standby power to meet strict standby power standard. OB2502P offers comprehensive protection coverage with auto-recovery feature including Cycle-by-Cycle current limiting, VDD over voltage protection, feedback loop open protection, short circuit protection, built-in leading edge blanking, VDD under voltage lockout (UVLO), OTP etc. OB2502P is offered in SOP8 packages.  Primary-side sensing and regulation without TL431 and opto-coupler  High precision constant voltage and current regulation at universal AC input  Multi-mode PWM/PFM operation for efficiency improving  Integrated 2A 650V MOSFET  Good dynamic response with synchronous rectifier application  Programmable CV and CC regulation  Built-in primary winding inductance compensation  Programmable cable drop compensation  No need for control loop compensation  Audio noise free operation  Built-in leading edge blanking (LEB)  Ultra low start-up current and low operating current  Comprehensive protection coverage with auto-recovery  On-chip OTP  VDD over voltage protection  VDD under voltage lockout with hysteresis (UVLO)  Cycle-by-Cycle current limiting  Feedback loop open protection  Output short circuit protection fid en tia lt o 华 能 宏 业 GENERAL DESCRIPTION tc on APPLICATIONS n- Br ig h Low Power AC/DC offline SMPS for  Cell Phone Charger  Digital Cameras Charger  Small Power Adapter  Auxiliary Power for PC, TV etc.  Linear Regulator/RCC Replacement O Figure.1. Typical CC/CV Curve TYPICAL APPLICATION ©On-Bright Electronics Confidential -1- Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch GENERAL INFORMATION Pin Configuration The pin map is shown as below for SOP8. VDD 1 8 Drain GND 2 7 Drain FB 3 6 Drain CS 4 5 Drain Absolute Maximum Ratings Parameter Drain Voltage (off state) VDD Voltage FB Input Voltage CS Input Voltage Min/Max Operating Junction Temperature TJ Operating Ambient Temperature TA Min/Max Storage Temperature Tstg Lead Temperature (Soldering, 10secs) 业 Ordering Information Part Number Description OB2502PCP SOP8, Pb-free, Tube OB2502PCPA SOP8, Pb-free in T&R Value -0.3V to Bvdss -0.3 to 28.5V -0.3 to 7V -0.3 to 7V -40 to 150 ℃ -20 to 85 ℃ -55 to 150 ℃ 260 ℃ 能 宏 Note: 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. 华 Package Dissipation Rating Package RθJA (℃/W) SOP8 90 fid en tia lt o Recommended Operating Condition Symbol Parameter Range VDD VDD Supply Voltage 8 to 25V X X X tc on OB2502P Package Package Pb free C:SOP8 P:Pb-free Packing Blank:Tube A: Tape/Reel O n- Br ig h High Precision CC/CV Primary-Side PWM Power Switch ©On-Bright Electronics Confidential -2- Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch Marking Information YWWZZZ OB2502PCP 华 能 宏 Y:Year Code WW:Week Code(01-52) ZZZ:Lot Code C:SOP8 Package P:Pb-free Package S:Internal Code(Optional) 业 S lt o TERMINAL ASSIGNMENTS Pin Name I/O Description 1 VDD P Power Supply 2 GND P Ground 3 FB I The voltage feedback from auxiliary winding. Connected to resistor divider from auxiliary winding reflecting output voltage. 4 CS I 5/6/7/8 Drain tc on fid en tia Pin Num. ig h Power MOSFET source Drain of internal power MOSFET O n- Br O ©On-Bright Electronics Confidential -3- Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch O n- Br ig h tc on fid en tia lt o 华 能 宏 业 BLOCK DIAGRAM ©On-Bright Electronics Confidential -4- Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch ELECTRICAL CHARACTERISTICS (TA = 25℃, VDD=15V, if not otherwise noted) Symbol Parameter Supply Voltage (VDD) Section I start-up Start up current Min VDD=UVLO_OFF-1V Max 485 Unit uA 0.68 1.0 mA 18.2 7.0 27.0 20.5 7.5 28.5 V V V 25 V 300 500 590 515 135 ns mV mV mV o 华 能 宏 业 16.0 6.5 26.0 2.475 2.500 2.525 V 2.0 305 340 us Hz KHz 45 50 uA 2048 V cycle 3.15 V 270 110 40 1.55 1024 2.85 3.0 O n- Br ig h tc on fid en tia UVLO(OFF) VDD under voltage lockout exit UVLO(ON) VDD under voltage lockout enter VDD_OVP VDD over voltage protection Max. Operating Voltage Current Sense Input Section TLEB LEB time Vth_ocp_min Minimum over current threshold Vth_ocp_max Maximum over current threshold Vcs_min CS minimum threshold FB Input Section Reference voltage for feedback Vref_FB threshold Tpause_min Minimum Toff F_min Minimum frequency F_max Maximum frequency Maximum cable compensation Icomp_cable current Vth_cc_shutdown CC mode shut down threshold Td_cc_shutdown CC mode shut down debounce Output Over Voltage Protection V_OVP Output Over voltage threshold MOSFET Section Mosfet Drain-Source Breakdown BVdss Voltage Static drain to source on Rdson resistance Typ. 5 Static current lt I static Test Conditions ©On-Bright Electronics Confidential -5- 650 V 4 Ώ Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch CHARACTERIZATION PLOTS Istatic(uA) VDD vs Istatic 800 700 600 500 400 300 200 100 0 2 4 6 8 10 12 14 16 18 20 22 业 VDD(V) 能 宏 7.50 7.30 华 7.10 6.50 -40 -10 20 50 80 110 140 tia lt o 6.90 6.70 en UVLO_7(ON)(V) UVLO_7(ON)(V) vs Tem perature on fid Temperature(℃) tc Vocp(V) vs Tem perature Br Vocp(V) ig h 2.600 2.540 2.480 n- 2.420 2.360 2.300 O Vref(V) Vref(V) vs Temperature -40 -10 20 50 80 0.480 0.440 0.400 -40 110 140 -10 20 50 80 110 140 Temperature(℃) Temperature(℃) ©On-Bright Electronics 0.600 0.560 0.520 Confidential -6- Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch Icable(uA) vs Temperature Ic a b le ( u A ) 48 46.4 44.8 43.2 41.6 40 -40 -10 20 50 80 110 140 Temperature(℃) MOSFET turn-on time, the load current is supplied from the output filter capacitor, Co, and the current in the primary winding ramps up. When MOSFET turns off, the energy stored in the primary winding is transferred to the secondary side and the current in the secondary winding is 能 宏 华 NP  IP NS o (1) The auxiliary voltage reflects the output voltage as shown in Figure.2 and it is given by fid en tia Startup Current and Start up Control Startup current of OB2502P 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. IS  lt OB2502P is a cost effective PSR power switch optimized for off-line low power AC/DC applications including battery chargers. It operates in primary side sensing and regulation, thus opto-coupler and TL431 are not required. Proprietary built-in CV and CC control can achieve high precision CC/CV control meeting most charger application requirements. 业 OPERATION DESCRIPTION V AUX  N AUX  (VO  V ) NS (2) tc on Where V indicates the voltage drop of the output Diode. O n- Br ig h Operating Current The operating current of OB2502P is as low as 680uA (typical). Good efficiency and les than 75mW standby power is achieved with the low operating current. CC/CV Operation OB2502P is designed to produce good CC/CV control characteristic as shown in the Figure. 1. In charger applications, a discharged battery charging starts in the CC portion of the curve until it is nearly full charged and smoothly switches to operate in CV portion of the curve. The CC portion provides output current limiting. In CV operation, the output voltage is regulated through the primary side control. In CC operation mode, OB2502P will regulate the output current constant regardless of the output voltage drop. Figure.2. Auxiliary voltage waveform Via a resistor divider connected between the auxiliary winding and FB (pin 2), the auxiliary voltage is sampled at the middle of the de-magnetization and it is hold until the next sampling. The sampled voltage is compared with reference voltage Vref (typical 2.5V) and the difference is amplified. The error amplifier output reflects the load condition and controls the switching off time to regulate the output voltage, thus constant output voltage can be achieved. When the sampled voltage is below Vref and the error amplifier output reaches its minimum, the switching frequency is controlled by the sampled Principle of Operation To support OB2502P series proprietary CC/CV control, system needs to be designed in DCM mode for flyback system (Refer to Typical Application Diagram in page1). In the DCM flyback converter, the output voltage can be sensed via the auxiliary winding. During ©On-Bright Electronics Confidential -7- Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch voltage to regulate the output current, thus the constant output current can be achieved. output current limit at higher AC voltage. In OB2502P , a proprietary OCP compensation block is integrated and no external components are needed. The OCP threshold in OB2502P series is a function of the switching ON time. For the ON time between 1.6us to 6.4us (typical), the OCP threshold changes linearly from 500mV to 590mV. For the ON time larger than 6.4us, the OCP threshold is clamped to 590mV, as shown in Figure 4. 华 能 宏 业 Adjustable CC Point and Output Power In OB2502P series, the CC point and maximum output power can be externally adjusted by external current sense resistor Rs at CS pin as illustrated in the typical application diagram. The larger Rs, the smaller CC point is, and the smaller output power becomes, and vice versa as shown in Figure.3. Figure.4. On time OCP compensation Figure.3. Adjustable output power by changing Rs lt o Programmable Cable Drop Compensation In OB2502P , cable drop compensation is implemented to achieve good load regulation. An offset voltage is generated at FB pin by an internal current flowing into the resister divider. The current is proportional to the switching off time, as a result, it is inversely proportional to the output load current, and the drop due to the cable loss can be compensated. As the load current decreases from full-load to no-load, the offset voltage at INV will increase. It can also be programmed by adjusting the resistance of the divider to compensate the drop for various cable lines used. The percentage of maximum compensation is Icomp _ cable  ( R1 // R2) 10 6 V  100% 2.5 Vout V is load compensation voltage and Vout is output voltage; For example: R1//R2=6.2Kohm, the percentage of maximum compensation is 1 LP FSW I p2 2 on (3) tc Po MAX  fid en tia Operation Switching Frequency The switching frequency of OB2502P is adaptively controlled according to the load conditions and the operation modes. For flyback operating in DCM, the maximum output power is given by O n- Br ig h Where Lp indicate the inductance of primary winding and Ip is the peak current of primary winding. Refer to the equation 3, the change of the primary winding inductance results in the change of the maximum output power and the constant output current in CC mode. To compensate the change from variations of primary winding inductance, the switching frequency is locked by an internal loop and the switching frequency is FSW  1 2TDemag (4) ∆V 45  6200 10 6  100%  11.16% Vout 2.5 Since TDemag is inversely proportional to the inductance, as a result, the product Lp and fsw is constant, thus the maximum output power and constant current in CC mode will not change as primary winding inductance changes. Up to ±7% variation of the primary winding inductance can be compensated. On Time OCP Compensation The variation of max output current in CC mode can be rather large if no compensation is provided. The OCP threshold value is self adjusted higher at higher AC voltage. This OCP threshold slope adjustment helps to compensate the increased ©On-Bright Electronics Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2502P . The switch current is detected by a Confidential -8- Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch sense resistor into the CS pin. An internal leading edge blanking circuit chops off the sensed voltage spike at initial power MOSFET on state so that the external RC filtering on sense input is no longer needed. controller will shut down. Protection Control Good power supply system reliability is achieved with its rich protection features including precise on-chip OTP, cycle-by-cycle current limiting (OCP), output over voltage protection, VDD over voltage protection, short circuit protection, under voltage lockout on VDD (UVLO). VDD is supplied by transformer auxiliary winding output. The output of OB2502P is shut down when VDD drops below UVLO (ON) and the power converter enters power on start-up sequence thereafter. O n- Br ig h tc on fid en tia lt o 华 能 宏 业 CC mode shutdown function In OB2500N, to prevent the controller operating under abnormal conditions, the minimum output voltage of CC mode is limited to predetermined voltage. The CC output voltage is sampled through FB pin from auxiliary winding at the middle of the de-magnetization. When the FB sampled voltage is below 1.55V and last 1024-2048 cycle, the ©On-Bright Electronics Confidential -9- Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side Power Switch Br ig h tc on fid en tia lt o 华 能 宏 业 PACKAGE MECHANICAL DATA A A1 A2 b c D E E1 e L θ Dimensions In Millimeters Min Max 1.350 1.750 0.050 0.250 1.250 1.650 0.310 0.510 0.100 0.250 4.700 5.150 3.800 4.000 5.800 6.200 1.270 (BSC) 0.400 1.270 0º 8º nO Symbol ©On-Bright Electronics Confidential - 10 - Dimensions In Inches Min Max 0.053 0.069 0.002 0.010 0.049 0.065 0.012 0.020 0.004 0.010 0.185 0.203 0.150 0.157 0.228 0.244 0.050 (BSC) 0.016 0.050 0º 8º Preliminary datasheet OB_DOC_DS_2502P01 OB2502P High Precision CC/CV Primary-Side 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. 能 宏 业 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. lt o 华 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 h tc on fid en tia 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 - 11 - Preliminary datasheet OB_DOC_DS_2502P01