LESHAN RADIO COMPANY, LTD. LR2257 AC/DC Current Mode PWM power management controller The LR2257 AC—DC is a high efficiency current-mode PWM power supply controller that drives an internal NPN transistor for high voltage switching. Apply with BiCMOS technology, the device consist of Bandgap reference voltage, Oscillator, High voltage switching transistor and build in safety features of over current and over voltage protection mechanisms Delivering up to 3W yet consumes, the typical application of the device will include: z z z z ¾ Lowest Total Cost Solution ¾ Low Power for Green Environments Protection, as lower as 0.3W ¾ Current Mode PWM ¾ Over-Current Protection, Over and Under-voltage Protection ¾ Emitter Drive of Internal Power Transistor ¾ 65kHz Switching Frequency Battery Charger, such as handset phone Power Adapter Offline Power Generator Etc. Absolute Maxim Ratings Item Symbol Typical Unit Power Supply VDD 9～12 V FB Start Voltage Vs 5 V FB Under-voltage Threshold Vu 3.5 V FB Clamp Voltage Vo 5.5 V FB input current IFB <1 mA Switching Frequency Fs 65 KHz Maximum Duty Cycle DMAX 75 ％ FB－SW Current Gain GF 0.3 A/V Current Limit ILIM 400 mA SW Break Down Voltage Vsw >400 V Stand By Current PS <0.3W W System Efficiency (Full Load) η >70 % 1/8 LESHAN RADIO COMPANY, LTD. LR2257 Pin Name 1：Feedback ： FB 5：Power Output : SW 2：Test Pin ： NC 6：Power Output : SW 3：Test Pin ： NC 7：Ground : Gnd 4：Power ： VDD 8：Ground: Gnd Pin Description Pin Symbol Pin Description 1 FB Feedback input 2,3 NC Test Pin * 4 VDD Power Supply 5,6 SW Power Transistor output 7,8 GND Ground *Note: Test2 should connect to Test3 while in application 2/9 LESHAN RADIO COMPANY, LTD. LR2257 Working Principle HI HI HV DC 6.2V DC 100uF T=8 10V 1 2 - 1 T=114 1M LO LO + 1N5817 1 2 T=24 2 1N4148 2 4 3 2 1N4148 D6 5.1V 2% 1 1 FB 8 GND 7 LR2257 SW 6 VDD 5 PC817A IC2 10uF 10V 22uF 35V Block Diagram VDD SW T1 T2 FB STARTER OSCILLATOR PROTECTION CIRCUIT R1 + + + R2 GATE DRIVER S Q R R3 VOLTAGE REFERENCE GND 3/8 LESHAN RADIO COMPANY, LTD. LR2257 Electrical Characteristics（Test condition：TA=25C,VFB＝4V ） Parameter Symbol Power Supply Test condition Min Typ Max Unit VDD 8.5 12 V FB Start Voltage Vs 5 FB Under-voltage Threshold Vu FB Clamp Voltage Vo FB input current V 3.25 3.5 3.65 10mA 5.2 5.5 5.8 V IFB - - 0.7 1 mA Switching Frequency Fs - - 70 - KHz Maximum Duty Cycle DMAX VFB =4V, ISW=10mA 70 75 80 % Minimum Duty Cycle DMIN VFB=4.6V, ISW=100mA 3.5 5.5 % Current Limit ILIM VFB=VUV+0.1V - 400 - mA FB to SW Current Gain GFB - -0.29 - A/V FB Dynamic Impedance RFB/VFB - 9 - KΩ SW Break Down Voltage Vsw >400 V Stand By Power PS <0.3 W System Efficiency (Full Load) η 74 % 4/8 LESHAN RADIO COMPANY, LTD. LR2257 Application 800mA R3 F1 L1 2.5mH C2 R 16 HI + 1k 4.7uF/400V 1M AC1 - R1 C1 200K 85-265VAC HI AC2 4.7uF/400V 100k 100 5 6 7 8 LR2257 4 C4 1N4007 D5 3 2 1 R5 4700pF/1KV R 5A 10uF/50V 220 C5 T=114 R7 T=24 T=8 680uF/10V 220 R9 510 R4 C7 1N5817 FR107 D6 C3 500pF 220 C6 10uF/50V R6 D7 1N4148 10nF PC817A C5 Q1 10nF C10 RT1 15 R8D 6.2 R8A 6.2 D 10 R 10 390 1uF 1K R 18 10k 5.1k C11 R12 IC2 TL431 5.6k R 13 L2 6u R 14 330uF/10V C13 L3 65u HI HI DC+ DC- 5/8 LESHAN RADIO COMPANY, LTD. LR2257 Characteristics Curve (%) 转η换效率 效 率与输出功率(VAC=110V) η VS Po (VAC=110V) 80% 70% 60% 50% 40% 30% 20% 10% 0% CV CC 0 1 2 3 4 5 6 Po (W) 输出功率（W） η (%) 转换效率 η效率与输出功率(VAC=220V) VS Po (VAC=220V) 80% 70% 60% 50% 40% 30% 20% 10% 0% CC CV 0 1 2 3 4 5 6 Po输出功 (W) 率（W） 6/8 LESHAN RADIO COMPANY, LTD. LR2257 EMI dBuV 80 70 60 EN55022A 50 40 30 20 10 150KHz Recommended 1MHz 10MHz 30MHz PCB LAYOUT 7/8 LESHAN RADIO COMPANY, LTD. LR2257 SO-8 Dimension Top View Right side View G A 8 7 6 5 I C B H D2257 J Front View Part A Part A A B C D E F G H 3 4 N M O inch Min. 0.1909 0.1515 0.2283 0.0480 0.0145 0.1472 0.0570 0.1889 2 L F DIM 1 K E D Max. 0.2007 0.1555 0.2441 0.0519 0.0185 0.1527 0.0649 0.2007 mm Min. 4.85 3.85 5.80 1.22 0.37 3.74 1.45 4.80 Max. 5.10 3.95 6.20 1.32 0.47 3.88 1.65 5.10 DIM I J K L M N O inch Min. 0.0019 0.0118 0.0074 0.0145 0.0118 0.0031 0.0000 Max. 0.0078 0.0275 0.0098 0.0204 0.0197 0.0051 0.0059 Min. 0.05 0.30 0.19 0.37 0.30 0.08 0.00 *Typical mm Max. 0.20 0.70 0.25 0.52 0.50 0.13 0.15 8/8