SG6848D

Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 FEATURES Green-Mode PWM Supports the “Blue Angel” Standard Low Start-up Current (5uA) Low Operating Current (2mA) Leading-Edge Blanking Constant Output Power Limit Universal Input Built-in Synchronized Slope Compensation Current Mode Operation Cycle-by-cycle Current Limiting Under Voltage Lockout (UVLO) Programmable PWM Frequency Gate Output Voltage Clamped at 15V Low Cost Few External Components Required Small SOT-26 Package DESCRIPTION This highly-integrated PWM controller provides several special enhancements designed to meet the low standby-power needs of low-power SMPS. To minimize standby power consumption, the proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. This green-mode function enables the power supply to easily meet even the strictest power conservation requirements. The BiCMOS fabrication process enables reducing the start-up current to 5uA, and the operating current to 2mA. To further improve power conservation, a large start-up resistance can be used. Built-in synchronized slope compensation ensures the stability of peak current mode control. Proprietary internal compensation provides a constant output power limit over a universal AC input range (90VAC to 264VAC). Pulse-by-pulse current limiting ensures safe operation even during short-circuits. To protect the external power MOSFET from being damaged by supply over voltage, the SG6848’s output driver is clamped at 15V. SG6848 controllers can be used to improve the performance and reduce the production cost of power supplies. The SG6848 is the best choice for replacing linear and RCC-mode power adapters. It is available in 8-pin DIP and 6-pin SOT-26 packages. APPLICATIONS General-purpose switching mode power supplies and flyback power converters, such as Battery chargers for cellular phones, cordless phones, PDAs, digital cameras, and power tools Power adapters for ink jet printers, video game consoles, and portable audio players Open-frame SMPS for TV/DVD standby and other auxiliary supplies, home appliances, and consumer electronics Replacements for linear transformers and RCC SMPS PC 5V standby power. TYPICAL APPLICATION From bridge rectifier 120~ 380VDC From auxiliary winding RIN 1.5M VDD FB C6 472p OUTPUT CIN 10u R7 100 SG6848 SENSE R9 95k RI GND RS 4.7 © System General Corp. Version 1.2(IRO33.0010.B0) -1- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 MARKING DIAGRAMS PIN CONFIGURATION SOT-26 MAYWW M: Mask Version Y: Year; WW: Work Week GND FB 1 8 XXXXXXX: Wafer Lot YY: Year; WW: Week V: Assembly Location GATE VDD NC 1 SENSE 1 2 3 4 RI 1 2 3 6 5 4 GATE VDD SENSE DIP-8 8 7 6 5 GND FB NC RI XXXXXXXYYWWV SG6848D ORDERING INFORMATION Part Number SG6848T SG6848D PWM Frequency 70kHz 70kHz Package 6-Pin SOT-26 8-pin DIP-8 PIN DESCRIPTIONS Name GATE VDD NC SENSE Pin No. DIP-8 / (SOT-26) Type Driver Output Supply Function The totem-pole output driver for driving the power MOSFET. Power supply. NC pin. Current sense. This pin senses the voltage across a resistor. When the voltage reaches 1 / (6) 2 / (5) 3 4 / (4) Analog Input the internal threshold, PWM output is disabled. This activates over-current protection. This pin also provides current amplitude information for current-mode control. A resistor connected from the RI pin to ground will generate a constant current source for the SG6848. This current is used to charge an internal capacitor, to determine the switching frequency. Increasing the resistance will reduce the amplitude of the current source and reduce the switching frequency. A 95kΩ r esistor Ri r esults in a 50uA constant current Ii and a 70kHz switching frequency. NC pin. RI 5 / (3) Analog Input/Output NC FB GND 6 7 / (2) 8 / (1) Analog Input Supply Feedback. The FB pin provides the output voltage regulation signal. It provides feedback to the internal PWM comparator, so that the PWM comparator can control the duty cycle. Ground. © System General Corp. Version 1.2(IRO33.0010.B0) -2- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 BLOCK DIAGRAM GND 8 (1) RI 5 (3) ON/OFF Driver Internal Bias VDD 1 (6) GATE VDD 2 (5) OSC SQ R OCP Comp Vlimit ramp Blanking Circuit 4 (4) SENSE + _ UVLO 16.3V/11.7V Green Mode Controller Slope Compensation PWM Comp 4.8V 7 (2) FB ABSOLUTE MAXIMUM RATINGS Symbol VDD Parameter DC Supply Voltage * Zener Clamp Zener Current Value 25 26 10 -0.3 to 6 V -0.3 to 6V 300 150 SOT-26 DIP-8 20 sec 10 sec SOT-26 DIP-8 208.4 82.5 -55 to +150 220 260 3.0 300 Unit V V mA V V mW ℃ °C/W °C/W ℃ °C kV V VFB VSense Pd TJ RθJA Tstg TL Input Voltage to FB Pin Input Voltage to Sense Pin P ower Dissipation Operating Junction Temperature Thermal Resistance (Junction to Air) Storage Temperature Range Lead Temperature (Soldering) ESD Capability, HBM Model ESD Capability, Model * All voltage values, except differential voltages, are given with respect to the network ground terminal. © System General Corp. Version 1.2(IRO33.0010.B0) -3- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 RECOMMENDED OPERATING CONDITIONS Symbol VDD Ta Parameter DC Supply Voltage Operating Ambient Temperature Value ≦ 20 -30 to +85 Unit V ℃ ELECTRICAL CHARACTERISTICS (TA = 25°C, VDD=15V) Feedback Input Section Symbol Ioz Vop Parameter Zero Duty Cycle Input Current Open Loop Voltage Test Condition Min. Typ. 1.3 4.5 Max. 2.0 Unit mA V Current Sense Section Symbol Zcs TPD VTH,FLT VTH,VALLEY Parameter Input Impedance D elay to Output Current Limit Flatten Threshold Voltage Current Limit Valley Threshold Voltage Test Condition Min. 10 Typ. 150 1.0 Max. 200 0.90 Unit kΩ nsec V V 0.80 0.85 Oscillator Section Symbol Fosc Fosc-green Ig In Sg Fdv Fdt Parameter Frequency Green-Mode Frequency Green-Mode FB Input Current Green-Mode Start Threshold FB Input Current In = 0.3mA for a Maximum Duty Cycle Green-Mode Modulation Slope Frequency Variation versus VDD D eviation Frequency Variation versus Temp. Deviation Test Condition RI=95kΩ RI=95kΩ Min. 65 Typ. 70 13 1.16 1 Max. 75 15 Unit kHz kHz mA mA Hz/uA RI=95kΩ VDD=12 to 20V TA=-30 to 85 ℃ 300 0.02 2 2 % % PWM Section Symbol DC (MAX) DC (MIN) Bnk Parameter Maximum Duty Cycle Minimum Duty Cycle Leading-Edge Blanking Time Test Condition Min. 70 - Typ. 75 1 250 Max. 80 2 Unit % % nsec Output Section Symbol Vol Voh tr tf VCLAMP Parameter Output Voltage Low Output Voltage High Rising Time Falling Time Output Clamp Voltage Test Condition VDD=15V, Io=20mA VDD=15V, Io=20mA VDD=15V, CL=1nF VDD=15V, CL=1nF VDD=20V Min. 8 Typ. Max. 1.5 Unit V V nsec nsec V 50 30 15 200 150 17 © System General Corp. Version 1.2(IRO33.0010.B0) -4- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 Under Voltage Lockout Section Symbol VTH(ON) VDD(min) Parameter Start Threshold Voltage Min. Operating Voltage Test Condition TA=25°C TA=25°C Min. 15.3 10.9 Typ. 16.3 11.7 Max. 17.3 12.5 Unit V V Total Standby Current Section Symbol IDD ST IDD OP Parameter Start-up Current Operating Supply Current Test Condition VDD=15V VDD=15V Min. Typ. 5 2 Max. 30 5 Unit uA mA © System General Corp. Version 1.2(IRO33.0010.B0) -5- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 TYPICAL CHARACTERISTICS Start-up Threshold Voltage (V TH(ON)) vs Tem perature 17.0 12.2 12.0 16.5 11.8 M in. Operating Voltage (V DD (min)) vs Temperature VDD (min) (V) -40 -25 -10 5 20 35 50 65 80 95 110 125 VTH(ON) (V) 16.0 11.6 11.4 11.2 11.0 10.8 15.5 15.0 14.5 10.6 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (℃ ) TEMPERATURE ( ℃ ) Start-up Crrent (IDD ST) vs Tem perature 30 74.0 25 72.5 20 PWM Oscillator Frequency (FOSC) vs Tem perature FOSC (KHz) -40 -25 -10 5 20 35 50 65 80 95 110 125 IDD ST (uA) 71.0 69.5 68.0 66.5 65.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 15 10 5 0 TEMPERATURE ( ℃ ) TEMPERATURE (℃ ) Frequency in green m ode (FOSC-green) vs Tem perature 15 14 80 79 78 M ax. Duty Cycle (DC(MAX)) vs Tem perature FOSC-green (KHz) DC (MAX) (%) 13 12 11 10 9 8 -40 -25 -10 5 20 35 50 65 80 95 110 125 77 76 75 74 73 72 71 70 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE ( ℃ ) TEMPERATURE ( ℃ ) © System General Corp. Version 1.2(IRO33.0010.B0) -6- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 PWM Oscillator Frequency (FOSC) vs. FB 80 70 60 F OSC (KHz) 50 40 30 20 10 0 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 FB (mA) © System General Corp. Version 1.2(IRO33.0010.B0) -7- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 OPERATION DESCRIPTION SG6848 devices integrate many useful designs into one controller for low-power switch-mode power supplies. The following descriptions highlight some of the features of the SG6848 series. switching frequency. Increasing the resistance will reduce the amplitude of the input current and reduce the switching frequency. A 95kΩ resistor Ri results in a 50uA constant current Ii and a 70kHz switching frequency. The relationship between Ri and the switching frequency is: fPWM = 6650 R I (k Ω ) ( kHz ) Start-up Current The start-up current is only 5uA. Low start-up current allows a start-up resistor with a high resistance and a low-wattage to supply the start-up power for the controller. A 1.5 MΩ, 0.25W, start-up resistor and a 10uF/25V VDD hold-up capacitor would be sufficient for an AC-to-DC power adapter with a wide input range (100VAC to 240VAC). The range of the oscillation frequency is designed to be within 50kHz ~ 100kHz. Leading-Edge Blanking Each time the power MOSFET is switched on, a turn-on spike will inevitably occur at the sense-resistor. To avoid premature termination of the switching pulse, a 250 nsec leading-edge blanking time is built in. Conventional RC filtering can therefore be omitted. During this blanking period, the current-limit comparator is disabled and it cannot switch off the gate driver. Operating Current The operating current has been reduced to 2mA. The low operating current results in higher efficiency and reduces the Vcc hold-up capacitance requirement. Constant Output Power Limit Green-Mode Operation The proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. On-time is limited to provide stronger protection against brownouts and other abnormal conditions. The feedback current, which is sampled from the voltage feedback loop, is taken as the reference. Once the feedback current exceeds the threshold current, the switching frequency starts to decrease. This green-mode function dramatically reduces power consumption under light-load and zero-load conditions. Power supplies using the SG6848 can easily meet even the strictest regulations regarding standby power consumption. When the SENSE voltage across the sense resistor Rs reaches the threshold voltage (around 1.0V), the output GATE drive will be turned off following a short propagation delay tD. This propagation delay will introduce an additional current proportional to tD*Vin/Lp. The propagation delay is nearly constant regardless of the input line voltage VIN. Higher input line voltages will result in larger additional currents. At high input line voltages, the output power limit will be higher than at low input line voltages. To compensate for this output power limit variation across a wide AC input range, the threshold voltage is adjusted by adding a positive ramp. This ramp signal rises from 0.85V to 1.0V, and then flattens out at 1.0V. A smaller threshold voltage forces the output GATE drive to terminate earlier. This reduces the total PWM turn-on time and makes the output power equal to that of low line input. This proprietary internal compensation ensures a constant output power limit for a wide AC input voltage range (90VAC to 264VAC). Oscillator Operation A resistor connected from the RI pin to ground will generate a constant current source for the SG6848. This current is used to charge an internal capacitor. The charge-time determines the internal clock speed and the © System General Corp. Version 1.2(IRO33.0010.B0) -8- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 Under Voltage Lockout (UVLO) The turn-on and turn-off thresholds of the SG6848 are fixed internally at 16.3V/11.7V. During start-up, the hold-up capacitor must be charged to 16.3V through the start-up resistor, so that the SG6848 will be enabled. The hold-up capacitor will continue to supply VDD until power can be delivered from the auxiliary winding of the main transformer. VDD must not drop below 11.7V during this start-up process. This UVLO hysteresis window ensures that hold-up capacitor will be adequate to supply VDD during start-up. Built-in Slope Compensation The sensed voltage across the current sense resistor is used for current mode control and pulse-by-pulse current limiting. Built-in slope compensation will improve stability and prevent sub-harmonic oscillations due to peak-current mode control. The SG6848 has a synchronized, positively-sloped ramp built-in at each switching cycle. The slope of the ramp is: 0.33 × Duty Duty(max) Gate Output The SG6848 BiCMOS output stage is a fast totem pole gate driver. Cross conduction has been avoided to minimize heat dissipation, increase efficiency, and enhance reliability. The output driver is clamped by an internal 15V Zener diode in order to protect power MOSFET transistors against undesired over-voltage gate signals. Noise Immunity Noise from the current sense or the control signal can cause significant pulse width jitter, particularly in continuous-conduction mode. While slope compensation helps alleviate these problems, further precautions should still be taken. Good placement and layout practices should be followed. Avoiding long PCB traces and component leads, locating compensation and filter components near the SG6848, and increasing the power MOS gate resistance is advised. © System General Corp. Version 1.2(IRO33.0010.B0) -9- www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 REFERENCE CIRCUIT Circuit 1 L F1 CX1 2- 1 L1 2 BD1 +4 C1 + R1 C2 1 C3 R5 R3 R4 10 T1 1,2 2 D4 1 1 L2 2 N VO 3 R2 22 D1 9 R10 8 5 C7 C8 + 1 U1 1 2 GND FB RI GATE VDD SENSE 6 5 4 R7 D5 2 + C9 1 3 Q1 7 3,4 C6 3 GND R6 R8 + R9 D2 1 2 C4 U2 4 3 1 2 R11 R13 R14 C10 U3 1 CY1 3 R12 2 BOM Reference BD1 CX1 CY1 C2 C1 C3 C4 C6 C7 C8 C9 C10 D1 D2 D4 D5 F1 L1 Component BD 1A/500V Reference L2 Q1 R1,R2 R4,R3 R5 R6 R7 R8 R10 R9 R11 R12 R13 R14 T1 U1 U2 U3 Component 10uH 6mm MOSFET 1A/600V R 750KΩ 1206 R 47KΩ 1206 R 47Ω 1206 R 4.7Ω 1206 R 100Ω 0805 R 10Ω 1206 (Optional) YC 472P/400V (Y1) (Optional) YC 102P/400V (Y1) EC 10uF/400V 105℃ CC 103P/500V CC 1000P/500V EC 10u/50V CC 472P 0805 (Optional) CC 102P/100V 1206 EC 470u/10V 105℃ EC 220u/10V 105℃ CC 222P 0805 Diode FRI07 Diode FR102 Diode SB360 (Optional) ZD 6.8V 0.5W R 1Ω/0.5W 20mH 6*8mm (Optional) R 10Ω 1206 R 100KΩ 0805 R 100Ω 1/8W R 33KΩ 0805 R 33KΩ 1/8W R 4.7KΩ 0805 EE-16 IC SG6848 (Green PWM IC) PC817 TL431 © System General Corp. Version 1.2(IRO33.0010.B0) - 10 - www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 PACKAGE INFORMATION 8 PINS -- DIP (D) D 8 5 Θ° E1 E e B 1 4 A1 A2 L b1 b e Dimensions Millimeters Min. Typ. 0.381 3.175 3.302 1.524 0.457 9.017 6.223 2.921 8.509 0˚ 9.271 7.620 6.350 2.540 3.302 9.017 7˚ 3.810 9.525 15˚ 0.115 0.335 0˚ 6.477 0.245 10.160 0.355 3.429 A Symbol A A1 A2 b b1 D E E1 e L eB θ˚ Max. 5.334 Inches Min. 0.015 0.125 Typ. Max. 0.210 0.130 0.060 0.018 0.365 0.300 0.250 0.100 0.130 0.355 7˚ 0.135 0.400 0.255 0.150 0.375 15˚ © System General Corp. Version 1.2(IRO33.0010.B0) - 11 - www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 SOT-26 (S) D b 6 4 Detail A E1 E 1 e1 e 3 c 1 R A2 A L A1 L1 1 Detail A Dimensions Symbol A A1 A2 b c D E E1 e e1 L L1 L2 R R1 θ˚ θ1˚ Millimeters Min. Typ. Max. 1.45 0.15 Inches Min. Typ. 0.90 0.30 0.08 1.15 1.30 0.50 0.22 0.036 0.011 0.003 0.045 2.90 2.80 1.60 0.95 1.90 0.30 0.45 0.60 0.25 0.10 0.10 0˚ 5˚ 4˚ 10˚ 0.25 8˚ 15˚ 0.004 0.004 0˚ 5˚ 0.60 0.020 0.114 0.110 0.063 0.037 0.075 0.018 0.024 0.010 0.010 4˚ 10˚ 8˚ 15˚ 0.024 © System General Corp. Version 1.2(IRO33.0010.B0) - 12 - θ L2 1 R θ θ Max. 0.057 0.006 0.051 0.020 0.009 www.sg.com.tw May.06, 2003 Product Specification Low Cost Green-Mode PWM Controller for Flyback Converters SG6848 DISCLAIMERS LIFE SUPPORT System General’s products are not designed to be used as components in devices intended to support or sustain human life. Use of System General’s products in components intended for surgical implant into the body, or other applications in which failure of System General’s products could create a situation where personal death or injury may occur, is not authorized without the express written approval of System General’s Chief Executive Officer. System General will not be held liable for any damages or claims resulting from the use of its products in medical applications. MILITARY System General's products are not designed for use in military applications. Use of System General’s products in military applications is not authorized without the express written approval of System General’s Chief Executive Officer. System General will not be held liable for any damages or claims resulting from the use of its products in military applications. RIGHT TO MAKE CHANGES System General reserves the right to change this document and/or this product without notice. Customers are advised to consult their System General sales representative before ordering. © System General Corp. Version 1.2(IRO33.0010.B0) - 13 - www.sg.com.tw May.06, 2003