OB2281AMP

OB2281A High Performance Current Mode PWM Controller GENERAL DESCRIPTION FEATURES OB2281A is a highly integrated current mode PWM control IC optimized for high performance, low standby power and cost effective offline flyback converter applications. PWM switching frequency at normal operation is internally fixed and is trimmed to tight range. At no load or light load condition, the IC operates in extended ‘burst mode’ to minimize switching loss. Lower standby power and higher conversion efficiency is thus achieved. VCC low startup current and low operating current contribute to a reliable power on startup and low standby design with OB2281A. OB2281A offers comprehensive protection coverage with auto-recovery including Cycle-byCycle current limiting (OCP), over load protection (OLP), VCC under voltage lockout (UVLO), over temperature protection (OTP), and over voltage protection (OVP). Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique. The tone energy at below 25KHz is minimized in the design and audio noise is eliminated during operation. OB2281A is offered in SOT23-6 package. ■ ■ ■ nf id en tia lt o 纽 莱 克 ■ ■ ■ Power on soft start reducing MOSFET Vds stress Frequency shuffling for EMI Extended burst mode control for improved efficiency and low standby power design Audio noise free operation Over Load operation with increased frequency Comprehensive protection coverage o VCC Under Voltage Lockout with hysteresis (UVLO) o VCC Over Voltage Protection (VCC OVP) o Cycle-by-cycle over current threshold setting for constant output power limiting over universal input voltage range o Over Load Protection (OLP) with autorecovery o External (if NTC resistor is connected at PRT pin)or internal Over Temperature Protection (OTP) o Output Over Voltage Protection(Output OVP) and the OVP triggered voltage can be adjusted by the resistor connected between auxiliary winding and PRT pin o Output diode short protection with autorecovery APPLICATIONS rig ht co Offline AC/DC flyback converter for ■ Printer, Storage power supply ■ Power Adapter O nB TYPICAL APPLICATION AC IN EMI Filter DC Out Vaux OB2281A GND GATE FB PRT ©On-Bright Electronics VCC CS Confidential -1- Datasheet OB_DOC_DS_2281AA0 OB2281A High Performance Current Mode PWM Controller Absolute Maximum Ratings Parameter Value GENERAL INFORMATION Pin Configuration GND 1 6 Gate FB 2 5 VCC PRT 3 4 CS Ordering Information Part Number Description OB2281AMP SOT23-6, Pb-free in T&R VCC DC Supply Voltage VOVP-1V FB Input Voltage -0.3 to 7V CS Input Voltage -0.3 to 7V PRT Input Voltage -0.3 to 7V Min/Max Operating Junction Temperature TJ -40 to 150 ℃ Operating Ambient Temperature TA -40 to 85 ℃ Min/Max Storage Temperature Tstg -55 to 150 ℃ 克 Lead Temperature 260 ℃ (Soldering, 10secs) Note: Stresses beyond those listed under 莱 Package Dissipation Rating Package RJA(℃/W) SOT23-6 200 nB rig ht tia lt co nf id en Recommended operating condition Symbol Parameter Range VCC VCC Supply Voltage 12 to 26V o 纽 “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. M:SOT23-6 P:Pb-free O Marking Information Y:Year Code WW:Week Code(01-52) ZZZ: Lot code A:Character Code S: Internal code ©On-Bright Electronics Confidential -2- Datasheet OB_DOC_DS_2281AA0 OB2281A High Performance Current Mode PWM Controller TERMINAL ASSIGNMENTS I/O Description GND P Ground FB I Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and the current-sense signal at Pin CS. PRT I Dual functions pin. Connecting a NTC resistor to ground for OTP detection. Connecting a resistor from Vaux can adjust OVP trigger voltage. If both OTP and OVP are needed, a diode should be connected between PRT pin and the NTC resistor. CS I Current sense input VCC P Power Supply Gate O Totem-pole gate driver output for power MOSFET O nB rig ht co nf id en tia lt o 纽 莱 克 Pin Name ©On-Bright Electronics Confidential -3- Datasheet OB_DOC_DS_2281AA0 OB2281A High Performance Current Mode PWM Controller FUNCTIONAL BLOCK DIAGRAM S VCC Vref& Iref AVDD Diode short Internal blocks OSC Diode short OCP Comparator OLP GND GATE o Temp sense tia lt Timer OTP OVP Diode short Slope compensation LEB CS AVDD 纽 PWM Comparator PK/Green/ Burst EX OTP Vocp 克 UVLO Soft Driver R OVP 莱 OVP Logic Control Q OLP FB Auto recovery nf id en PRT O nB rig ht co EX OVP ©On-Bright Electronics Confidential -4- Datasheet OB_DOC_DS_2281AA0 OB2281A High Performance Current Mode PWM Controller ELECTRICAL CHARACTERISTICS (TA = 25℃, VCC=18V, unless otherwise noted) Symbol Parameter Supply Voltage (VDD) Istartup VCC Start up Current I_VCC_Operation Operation Current I_VCC_Burst Burst Current UVLO(OFF) VCC Under Voltage Lockout Enter VCC Under Voltage Lockout Exit (Recovery) Pull-up PMOS active 6.5 Typ. Max Unit 2 5 uA 2.5 3 mA 0.55 0.75 mA 7.3 V 8.1 14.7 16.2 17.7 V V 莱 10 FB=3V,CS=0V. Slowly VCC Over Voltage Protection OVP ramp VCC, until no 26.5 28 threshold voltage gate switching. Feedback Input Section(FB Pin) VFB_Open VFB Open Loop Voltage 5.1 Avcs PWM input gain ∆VFB/∆VCS 3.5 Maximum duty Max duty cycle @ 75 80 cycle VCC=18V,VFB=3V,VCS=0V Vref_green The threshold enter green mode 2.1 Vref_burst_H The threshold exits burst mode 1.33 The threshold enters burst Vref_burst_L 1.23 mode Short FB pin to GND IFB_Short FB pin short circuit current 0.21 and measure current Open loop protection, FB VTH_OLP 4.4 Threshold Voltage Open loop protection, Td_OLP 15 Debounce Time ZFB_IN Input Impedance 30 Current Sense Input(CS Pin) SST_CS Soft start time for CS peak 4 T_blanking Leading edge blanking time 300 From Over Current Over Current Detection and Occurs till the Gate Td_OC 90 Control Delay driver output start to turn off Internal Current Limiting VTH_OC Threshold Voltage with zero 0.43 0.45 duty cycle VTH_OC_Clamp OCP CS voltage clamper 0.72 Over Current protection Td_OCP 60 debounce Time PRT pin IRT Output current for external OTP 92 100 29.5 V V V/V 85 rig ht V nB mA V O ©On-Bright Electronics Confidential -5- % V V co nf id en tia lt o 纽 Vpull-up Min VCC=UVLO(OFF)-1V, measure leakage current into VCC VDD=18V,CS=4V, FB=3.5V,measure I(VCC) CS=0V,FB=0.5V, measure I(VCC) 克 UVLO(ON) Test Conditions ms KΩ ms ns ns 0.47 V V ms 108 uA Datasheet OB_DOC_DS_2281AA0 OB2281A High Performance Current Mode PWM Controller VOTP Ioutput_ovp Td_output_ovp In-chip OTP OTP enter detection Threshold voltage for external OTP Current threshold for adjustable output OVP Output OVP debounce time 0.95 1 OTP exit Oscillator Normal Oscillation Frequency Fosc_PK Peak frequency SST_freq Soft start time of frequency ᇞf_OSC Frequency jittering F_shuffling Shuffling frequency ᇞf_Temp Frequency Stability ᇞf_VCC Frequency Voltage Stability F_Burst Gate driver Burst Mode Switch Frequency VOH V_clamping T_r T_f 60 莱 纽 o tia lt Output low level @ VDD=18V, Io=5mA Output high level @ VCC=18V, Io=20mA Output clamp voltage Output rising time 1.2V ~ 10.8V @ CL=1000pF Output falling time 10.8V ~ 1.2V @ CL=1000pF ©On-Bright Electronics Confidential -6- V 60 uA 5 Cycles 150 ℃ 130 ℃ 65 70 KHz 130 KHz 30 ms +/-6 % 32 Hz 1 % 1 % 25 KHz nB rig ht co nf id en Temperature O VOL VDD=18V,FB=3V, CS=0V VDD=18V,FB=4.5V, CS=0V 克 FOSC 1.05 1 6 V V 11.5 V 150 ns 50 ns Datasheet OB_DOC_DS_2281AA0 OB2281A High Performance Current Mode PWM Controller CHARACTERIZATION PLOTS VDD = 18V, TA = 25℃ condition applies if not otherwise noted. UVLO(ON)(V) vs Tem perature UVLO(OFF)(V) vs Tem perature 27 UVLO(OFF)(V) UVLO(ON)(V) 9 8.8 8.6 8.4 8.2 25.2 23.4 21.6 19.8 8 18 -40 -10 20 50 80 110 140 -40 -10 80 110 140 Temperature(℃) Fosc_nom (Khz) vs Tem perature 莱 Vref_otp(V) vs Tem perature 73 Vref_otp(V) 1.06 1.02 tia lt o 67.8 纽 1.1 70.4 65.2 62.6 60 -40 -10 20 50 80 nf id en Fosc_nom(Khz) 50 克 Temperature(℃) 20 0.98 0.94 0.9 -40 110 140 20 50 80 110 140 Temperature(℃) co Temperature(℃) -10 0.5 nB 104 98 Vth_oc(V) 110 92 O IRT(uA) Vth_oc(V) vs Tem perature rig ht IRT(uA) vs Tem perature 86 80 0.48 0.46 0.44 0.42 0.4 -40 -10 20 50 80 110 140 -40 Temperature(℃) ©On-Bright Electronics -10 20 50 80 110 140 Temperature(℃) Confidential 7 Datasheet OB_DOC_DS_2281AA0 OB2281A High Performance Current Mode PWM Controller OPERATION DESCRIPTION OB2281A is a highly integrated current mode PWM control IC optimized for high performance, low standby power and cost effective offline flyback converter applications. The ‘extended burst mode’ control greatly reduces the standby power consumption and helps the design easier to meet the international power conservation requirements. supply is from switching loss of the MOSFET, the core loss of the transformer and the loss of 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 frequency reduces at light/no load condition to improve the conversion efficiency. At light load or no load condition, the FB input drops below Vref_burst_L (the threshold enter burst mode) and device enters Burst Mode control. The Gate drive output switches when FB input rises back to Vref_burst_H (the threshold exit burst mode). Otherwise the gate drive remains at off state to minimize the switching loss and reduces the standby power consumption to the greatest extend. 莱 克  Startup Current and Start up Control Startup current of OB2281A is designed to be very low so that VCC 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. o 纽  Operating Current The Operating current of OB2281A is low at 2.5mA (typical). Good efficiency is achieved with OB2281A low operation current together with the ‘extended burst mode’ control features. tia lt  Oscillator Operation During the full load power operation, OB2281A operates at a 65KHz (typical) fixed frequency. The efficiency and system cost is controlled at an optimal level. In over load mode, frequency is increased from 65KHz (typical) to 130KHz (typical). At light load levels, OB2281A enters the light load mode, where the output current is reduced. The switching losses are reduced by lowering the switching frequency. rig ht co nf id en  Soft Start OB2281A 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 VCC reaches UVLO(OFF), the CS peak voltage is gradually increased from 0.05V to the maximum level. Every restart up is followed by a soft start. O nB  Frequency shuffling for EMI improvement The frequency shuffling (switching frequency modulation) is implemented in OB2281A. 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.  Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2281A current mode PWM control. The switch current is detected by a sense resistor into the CS 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 power MOSFET. The current limiting comparator is disabled and cannot turn off the internal power MOSFET during the blanking period. The PWM  Extended Burst Mode Operation At light load or no load condition, most of the power dissipation in a switching mode power ©On-Bright Electronics Confidential 8 Datasheet OB_DOC_DS_2281AA0 OB2281A High Performance Current Mode PWM Controller duty cycle is determined by the current sense input voltage and the FB input voltage. On-Bright proprietary dual function of external OTP and output OVP provides feasible and accurate detection of external OTP through NTC resistor and output OVP. The dual function is realized through time-division technology as shown in the figure. For external OTP detection, when switch control signal S1= “1”, about 20uA (typical) current flows out from PRT pin. When switch control signal S0= “1”,about 120uA (typical) current flows out from PRT pin. The PRT pin voltage difference △Votp at phase S0 and S1 phase is equal to RT  ROVP VOTP   100uA . ROVP  RT When △Votp