SG6858 Low-Cost, Green-Mode, PWM Controller for Flyback Converters Features 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 greenmode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. This green-mode function enables the power supply to meet even the strictest power conservation requirements. Green-Mode PWM Supports the ”Blue Angel” Standard Low Startup Current: 10µA (Maximum) Low Operating Current: 2.5mA Leading-Edge Blanking (LEB) Constant Output Power Limit Built-in Synchronized Slope Compensation Current-Mode Operation Cycle-by-Cycle Current Limiting Under-Voltage Lockout (UVLO) Programmable PWM Frequency VDD Over-Voltage Protection with Auto-Restart Gate Output Voltage Clamped at 17V Few External Components Required SSOT-26 and DIP-8 Packages Available Applications 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, PC 5V standby power, and consumer electronics Replacements for linear transformers and RCC SMPS Offline High Brightness (HB) LED drivers The BiCMOS fabrication process enables reducing the startup current to 10µA and the operating current to 2.5mA. To further improve power conservation, a large startup resistance can be used. Built-in synchronized slope compensation ensures the stability of peakcurrent-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 output driver is clamped at 17V. SG6858 controllers can improve the performance and reduce the production cost of power supplies. The SG6858 replaces linear and RCC-mode power adapters. It is available in 8-pin DIP and 6-pin SSOT-26 packages. Ordering Information Part Number Operating Temperature Range Eco Status Package Packing Method SG6858TZ -40 to +125°C RoHS 6-Pin SSOT-26 Tape & Reel SG6858DZ -40 to +125°C RoHS 8-Pin DIP-8 Tube For Fairchild’s definition of Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html. © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 www.fairchildsemi.com SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters September 2009 Bridge Rectifier Diode L EMI AC Input Filter + N RSN2 CSN2 CSN CBulk RSN RStart DVDD NP NS VO + DR + CO1 CO2 ZDO DSN + CVDD VO- NA 5 VDD GATE 6 3 RI RRI RG SG6858 2 FB SENSE 4 GND CFB CLF 1 RLF RSENSE Rd R1 PC817 CF RF TL431 R2 Figure 1. Typical Application Block Diagram GND RI 1(8) 3(5) VDD OVP Soft Driver 25V OSC S SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Typical Application 6(1) GATE Q R VDD 5(2) Internal BIAS Vlimit ramp + UVLO Slope Compensation 16.5V/11.5V 3R Green Mode Controller Blanking Circuit 4(4) SENSE 5V 2(7) FB 2R SOT(DIP) Figure 2. Block Diagram © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 www.fairchildsemi.com 2 XXX:AAI=SG6858 TT: Die run code ●: Year code — : Week code Figure 3. SSOT-26 F: Fairchild Logo Z: Assembly Plant Code X: Year Code Y: Week Code TT: Die Run Code T: N=DIP P: Y=Green Package M: Manufacture flow code Figure 4. DIP-8 Pin Configuration GND 1 6 GAT E FB 2 5 VDD RI 3 4 GATE 1 8 GND VDD 2 7 FB NC 3 6 NC SE NSE 4 5 RI SENSE SOT - 26 DIP-8 Figure 5. Pin Configurations SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Marking Information Pin Definitions Pin # Name Description DIP-8 SSOT-26 1 6 GATE 2 5 VDD Power supply. NC No connection. 3 4 5 Totem-pole output driver for the power MOSFET. 4 Current sense. This pin senses the voltage across a resistor. When the voltage SENSE reaches the internal threshold, PWM output is disabled. This activates over-current protection. This pin provides current amplitude information for current-mode control. 3 RI A resistor connected from the RI pin to ground generates a constant current source. This current is used to charge an internal capacitor to determine the switching frequency. Increasing the resistance reduces the amplitude of the current source and reduces the switching frequency. A 95kΩ resistor, RI, results in a 50µA constant current, II, and a 70kHz switching frequency. NC No connection. Feedback. The FB pin provides the output voltage regulation signal, and feedback to the internal PWM comparator, so the PWM comparator can control the duty cycle. 6 7 2 FB 8 1 GND © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 Ground. www.fairchildsemi.com 3 Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. All voltage values, except differential voltages, are given with respect to GND pin. Symbol Parameter Min. Max. Unit VDD Supply Voltage 30 V VFB Input Voltage to FB Pin -0.3 7.0 V Input Voltage to SENSE Pin -0.3 7.0 V VSENSE RΘJC TJ TSTG TL ESD Thermal Resistance (Junction-to-Case) SSOT 208.4 DIP 82.5 °C/W Operating Junction Temperature -40 +125 °C Storage Temperature Range -55 +150 °C 260 °C Lead Temperature, Wave Soldering, 10 Seconds Electrostatic Discharge Capability Human Body Model, JESD22-A114 3.0 Machine Model, JESD22-A115 0.2 kV Recommended Operating Conditions The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to Absolute Maximum Ratings. Symbol Parameter VDD DC Supply Voltage TA Operating Ambient Temperature © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 Min. -40 Max. Unit 22 V +125 °C SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Absolute Maximum Ratings www.fairchildsemi.com 4 VDD=15V, TA=-40°C ~+125°C (TA= TJ), unless otherwise specified. Symbol Parameter Test Condition Min. Typ. Max. Unit 22 V VDD Section VDD-OP Continuously Operating Voltage VDD-ON Turn-On Threshold Voltage 15.5 16.5 17.5 V VDD-OFF Turn-Off Voltage 10.5 11.5 12.5 V IDD-ST Startup Current VDD=VDD-ON – 0.1V 10 15 µA IDD-OP Operating Supply Current VDD=15V, GATE with 1nF to GND 2.5 3.5 mA 23 25 26 V 50 125 200 µsec VDD-OVP VDD Over-Voltage Protection Level tD-VDDOVP VDD OVP Debounce Time VDD-G OFF VDD Low Threshold Voltage to Exit Green Off Mode VDD-OFF VDD-OFF VDD-OFF + 0.95 + 1.10 + 1.25 V 2/5 V/V 5 kΩ Feedback Input Section AV FB Input to Current Comparator Attenuation ZFB Input Impedance VFB-OPEN FB Pin Open High Voltage 4.5 5.0 5.5 V VFB-N Green Mode Entry FB Voltage 2.85 V VFB-G Green Mode Ending FB Voltage 2.20 V 75 Hz/mV SG Green Mode Modulation Slope RI=95kΩ Current Sense Section ZSENSE Input Impedance tPD Delay to Output VSTHFL Flat Threshold Voltage for Current Limit VSTHVA Valley Threshold Voltage for Current Limit tLEB DCYSAW 10 kΩ 60 110 0.96 Leading-Edge Blanking Time V 0.75 0.80 0.85 V 240 300 360 ns Maximum Duty Cycle Duty Cycle of SAW Limit ns 45 SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Electrical Characteristics % Oscillator Section fOSC Frequency RI=95kΩ Green Mode Frequency RI=95kΩ fDV Frequency Variation vs. VDD Deviation VDD=13.5V to 22V fDT Frequency Variation vs. Temperature Deviation TA=-40°C ~+125°C fOSC-G 65 70 75 22 0 0.02 kHz kHz 2.00 % 2 % 80 % 1.5 V Output Section DCYMAX Maximum Duty Cycle VGATE-L Output Voltage Low VDD=15V, IO=20mA Output Voltage High VDD=13.5V, IO=20mA tR Rising Time VDD=13.5V, CL=1nF 100 170 240 ns tF Falling Time VDD=13.5V, CL=1nF 35 55 75 ns Output Clamp Voltage VDD=13.5V, TA=25°C 16 17 18 V VGATE-H VGATE-CLAMP © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 70 75 8 V www.fairchildsemi.com 5 Turn-On Threas hold Voltage (V DD-O N ) v s Turn-off Thres hold Voltage (V DD-OF F ) v s Tem perature Tem perature 17.5 12.5 12.1 V DD-O FF (V) V DD-O N (V) 17.0 16.5 16.0 11.7 11.3 10.9 15.5 10.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 Tem perature (℃) Figure 6. Turn-On Threshold Voltage (VDD-ON) vs. Temperature -10 5 35 50 65 80 95 110 125 Operating Supply Current (IDD-O P ) v s Tem perature 3.5 15 3.0 IDD-O P (m A) 20 10 5 2.5 2.0 0 1.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature (℃) Temperature (℃) Figure 8. Startup Current (IDD-ST) vs. Temperature Figure 9. Operating Supply Current (IDD-OP) vs. Temperature Frequenc y (F O S C ) v s Tem perature M ax im um Duty Cy c le (DCY MA X ) v s Tem perature 75 80 73 78 DCY MA X (%) F O S C (KHz ) 20 Tem perature (℃) Figure 7. Turn-Off Threshold Voltage (VDD-OFF) vs. Temperature Startup Current(IDD-S T ) v s Temperature IDD-S T (uA) -25 SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Typical Performance Characteristics 71 69 67 76 74 72 65 70 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 Temperature (℃) -10 5 20 35 50 65 80 95 110 125 Temperature (℃) Figure 10. Frequency (fOSC) vs. Temperature © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 -25 Figure 11. Maximum Duty Cycle (DCYMAX) vs. Temperature www.fairchildsemi.com 6 Green-M ode Entry FB Voltage(V FB -N ) v s Green-M ode Ending FB Voltage (V FB -G ) v s Temperature Tem perature 3.2 2.50 3.1 2.40 V FB -G (V) V FB -N (V) 3.0 2.9 2.8 2.7 2.6 2.30 2.20 2.10 2.00 VDD=15V VDD=15V 1.90 2.5 -40 -25 -10 5 20 35 50 65 80 95 110 -40 125 -25 -10 5 35 50 65 80 95 110 125 Tem perature (℃) Tem perature (℃) Figure 12. Green Mode Entry FB Voltage (VFB-N) vs. Temperature Figure 13. Green Mode Ending FB Voltage (VFB-G) vs. Temperature Operation Current (IDD-OP ) vs VDD Voltage Leading-Edge Blank ing Time (t L E B ) v s Tem perature 3.5 350 330 3.0 IDD-OP (m A) t L E B (ns ec ) 20 310 290 270 2.5 2.0 VDD=15V 250 1.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 12 13 14 Tem perature (℃) 16 17 18 19 20 21 22 23 VDD Voltage (V) Figure 14. Leading-Edge Blanking Time (tLEB) vs. Temperature © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 15 Figure 15. Operating Current (IDD-OP) vs. Temperature 24 SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Typical Performance Characteristics (Continued) www.fairchildsemi.com 7 SG6858 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 SG6858 series. Startup Operation The startup current is only 10µA. Low startup current allows a startup resistor with a high resistance and low wattage to supply the startup power for the controller. A 1.5MΩ, 0.25W, startup resistor and a 10µF/25V VDD hold-up capacitor would be sufficient for an AC-to-DC power adapter with a wide input range (100VAC to 240VAC). Operating Current The operating current has been reduced to 2.5mA. The low operating current results in higher efficiency and reduces the VDD hold-up capacitance requirement. Figure 16. Current Sense R-C Filter Constant Output Power Limit When the SENSE voltage across the sense resistor RS reaches the threshold voltage (around 0.96V), the output GATE drive is turned off following a short propagation delay tPD. 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 zeroload conditions. Power supplies using the SG6858 meet the strictest regulations regarding standby power consumption. This propagation delay introduces an additional current proportional to tPD•VIN/LP. The propagation delay is nearly constant regardless of the input line voltage VIN. Higher input line voltages result in larger additional currents. At high input line voltages, the output power limit is 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 (VLIMIT_RAMP). This ramp signal rises from 0.80V to 0.96V, then flattens out at 0.96V. 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 generates a constant current source for the SG6858. This current is used to charge an internal capacitor. The charge-time determines the internal clock speed and the switching frequency. Increasing the resistance reduces the amplitude of the input current and reduces the switching frequency. A 95kΩ resistor RI results in a 50µA constant current II and a 70kHz switching frequency. The relationship between RI and the switching frequency is: f PWM = 6650 R I (k Ω ) (kHz ) Under-Voltage Lockout (UVLO) The turn-on and turn-off thresholds are fixed internally at 16.5V/11.5V. During startup, the hold-up capacitor must be charged to 16.5V through the startup resistor, so that the SG6858 is enabled. The hold-up capacitor continues to supply VDD until power can be delivered from the auxiliary winding of the main transformer. VDD must not drop below 11.5V during this startup process. This UVLO hysteresis window ensures that the hold-up capacitor is adequate to supply VDD during startup. (1) Leading-Edge Blanking (LEB) Each time the power MOSFET is switched on, a turn-on spike occurs at the sense-resistor. To avoid premature termination of the switching pulse, a 300ns leadingedge 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. © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Operation Description www.fairchildsemi.com 8 Built-in Slope Compensation Integrated VDD over-voltage protection prevents damage due to over-voltage conditions. When the VDD exceeds the internal threshold due to abnormal conditions, PWM output is turned off until the VDD voltage drops below the UVLO, then starts again. Over-voltage conditions are usually caused by open feedback loops. The sensed voltage across the current sense resistor is used for current mode control and pulse-by-pulse current limiting. Built-in slope compensation improves stability and prevents sub-harmonic oscillations due to peak-current mode control. The SG6858 has a synchronized, positively-sloped ramp built-in at each switching cycle. The slope of the ramp is: Gate Output 0.36 × Duty Duty (max .) The 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 17V Zener diode to protect power MOSFET transistors against undesired over-voltage gate signals. © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 (2) Noise Immunity Noise from the current sense or the control signal can cause significant pulsewidth jitter, particularly in continuous-conduction mode. While slope compensation helps alleviate this problem, further precautions should be taken. Good placement and layout practices should be followed. Avoiding long PCB traces and component leads, locating compensation and filter components near the SG6858, and increasing the power MOS gate resistance are advised. SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters VDD Over-Voltage Protection (OVP) www.fairchildsemi.com 9 Application Fairchild Devices Input Voltage Range Output Adapter SG6858 90~264VAC 12V/1.25A (15W) F1 L IN4007*4 1A/250V R XC1 XC 1MΩ AC Input RXC2 0.22µF/300V 1MΩ + RSN 66kΩ CBulk RStart 1.5MΩ N RVDD NA 1.2Ω 10nF/1KV CSN 22µF/400V FR103 10µF/50V DVDD + CVDD NP 47Ω 1nF RSN2 CSN2 470µF/16V DR + + NS MBR10100CT CO1 CO2 VO- 47Ω RSN 680µF/16V DSN UF1003 10Ω SSP2N60 RG 5 100kΩ VDD 3 RI RRI RSENSE GATE 6 VO + 1.5Ω 38.3kΩ R1 Rd 560Ω SG6858 2 FB PC817 SENSE 4 GND RF 1 CY 2.2nF Figure 17. TL431 1% CF 20kΩ 2.2nF 10kΩ R2 Schematic of Application Circuit Transformer - Core: EF-20 - Primary-Side Inductance: 2mH (Pin1 to Pin3) 1 N1 105Turns 3 4 0.27Φ*1 N2 18Turns 0.3Φ*2 SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Typical Application Circuit (Flyback Converter for Printer Application) TP+ Shielding lead to Pin 2 N3: 2-4 Shielding lead to Pin 2 N2: TP – - TP+ Shielding lead to Pin 2 N1: 1-3 TP– N3 22Turns 0.25Φ*1 2 Figure 18. © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 Transformer Structure www.fairchildsemi.com 10 SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Physical Dimensions Figure 19. 6-Pin, SSOT-6 Package Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/. © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 www.fairchildsemi.com 11 SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters Physical Dimensions (Continued) 9.83 9.00 6.67 6.096 8.255 7.61 3.683 3.20 5.08 MAX 7.62 0.33 MIN 3.60 3.00 (0.56) 2.54 0.56 0.355 0.356 0.20 9.957 7.87 1.65 1.27 7.62 NOTES: UNLESS OTHERWISE SPECIFIED A) THIS PACKAGE CONFORMS TO JEDEC MS-001 VARIATION BA B) ALL DIMENSIONS ARE IN MILLIMETERS. C) DIMENSIONS ARE EXCLUSIVE OF BURRS, MOLD FLASH, AND TIE BAR EXTRUSIONS. D) DIMENSIONS AND TOLERANCES PER ASME Y14.5M-1994 E) DRAWING FILENAME AND REVSION: MKT-N08FREV2. Figure 20. 8-Pin, Dual-Inline Package (DIP-8) Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/. © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 www.fairchildsemi.com 12 SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters © 2008 Fairchild Semiconductor Corporation SG6858 • Rev. 1.2.4 www.fairchildsemi.com 13