SG6858DZ资料

Product Specification

SG6858

Low-Cost, Green-Mode PWM Controller for Flyback Converters FEATURES

󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄 󰂄

Green-mode PWM

Supports the “Blue Angel” standard Low start-up current (10µA) Low operating current (2.5mA) 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

VDD over-voltage protection (auto restart) Gate output voltage clamped at 17V Low cost

Few external components required Small SOT-26 and DIP-8 packages

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 meet even the strictest power conservation requirements. The BiCMOS fabrication process enables reducing the start-up current to 10µA and the operating current to 2.5mA. 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 2VAC). 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 events, the SG6858’s output driver is clamped at 17V. SG6858 controllers can be used to improve the performance and reduce the production cost of power supplies and can replace 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

auxiliary supplies, home appliances, and consumer electronics

󰂄 Replacements for linear transformers and RCC SMPS 󰂄 PC 5V standby power

TYPICAL APPLICATION

© System General Corp.

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Product Specification SG6858 Low-Cost, Green-Mode PWM Controller for Flyback Converters MARKING DIAGRAMS PIN CONFIGURATION ORDERING INFORMATION Part Number SG6858TZ SG6858DZ XXXXXXXXYWWV AAImw AAI: SG6858 m: Mask Version w: Week code A~Z=W1~W26 A~Z=W27~W52 : Lead Free Package SOT-26 GND FBRIDIP-8 GATE VDD SENSE SG6858DP D: D=DIP P: Z=Lead Free Null=Regular Package XXXXXXXX: Wafer Lot Y: Year; WW: Week V: Assembly Location GATEVDDNCSENSEGND FB NC RI Pb-Free Package 6-pin SOT-26 8-pin DIP-8 PIN DESCRIPTIONS Name GATE VDD Type Function DIP-8 SOT-26 1 2 6 5 Driver Output Supply The totem-pole output driver for driving the power MOSFET. Power supply. Pin No. NC 3 SENSE 4 4 No Connection NC pin. Analog Input Current sense. This pin senses the voltage across a resistor. When the voltagereaches 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 generates a constant current source used to charge an internal capacitor and determines the switching frequency. Increasing the resistance reduces the amplitude of the current source and reduce the switching frequency. A 95kΩ resistor, RI, results in a 50µA constant current II and a 70kHz switching frequency. RI 5 3 Analog Input/Output NC 6 FB 7 2 GND 8 1 No Connection NC pin. Feedback. The FB pin provides the output voltage regulation signal. It provides Analog Input feedback to the internal PWM comparator, so that the PWM comparator cancontrol the duty cycle. Supply Ground. © System General Corp.

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Product Specification

SG6858

Low-Cost, Green-Mode PWM Controller for Flyback Converters BLOCK DIAGRAM

© System General Corp.

Version 1.2.1 (IAO33.0045.B2)

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Product Specification SG6858 Low-Cost, Green-Mode PWM Controller for Flyback Converters ABSOLUTE MAXIMUM RATINGS Symbol Parameter VVDD VFB VSENSE TJ RθJA TSTG TL VESD-HBM VESD-MM DC Supply Voltage* Input Voltage to FB Pin Input Voltage to Sense Pin Operating Junction Temperature Thermal Resistance (Junction-to-Air) Storage Temperature Range Lead Temperature (Wave Soldering or Infrared, 10 Seconds) Electrostatic Discharge Capability, Human Body Model Electrostatic Discharge Capability, Machine Model Value 30 -0.3 to 7.0 -0.3 to 7.0 -40 to +125 Unit V V V °C SOT 208.4 °C/W DIP 82.5 °C/W -55 to +150 260 3.0 200 °C °C kV V * All voltage values, except differential voltages, are given with respect to GND pin. * Stresses beyond those listed under \"absolute maximum ratings\" may cause permanent damage to the device. RECOMMENDED OPERATING CONDITIONS Symbol Parameter VDD DC Supply Voltage TA Operating Ambient Temperature Value -20 to +85 Unit °C ≦22 V * For proper operation. ELECTRICAL CHARACTERISTICS VDD=15V, TA = 25°C, unless otherwise noted. VDD Section Symbol Parameter VDD-OP VDD-OFF Continuously Operation Voltage Turn-off Threshold Voltage VDD-ON Turn-on Threshold Voltage IDD-ST Start-up Current IDD-OP Operating Supply Current VDD-OVP tD-VDDOVP VDD-G OFF VDD Over-Voltage Protection Level VDD Low Threshold Voltage to Exit Green-off Mode Test Condition VDD=VDD-ON – 0.1V VDD=15V, GATE with 1nF to GND Min. Typ. Max. Unit 10.5 11.5 10 22 12.5 15 V V µA 15.5 16.5 17.5 V 2.5 3.5 mA 24 25 26 V 50 VDD-OFF + 0.95 125 200 µs V VDD-OFF + VDD-OFF + 1.10 1.25 VDD Over-Voltage Protection Debounce © System General Corp.

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Product Specification SG6858 Low-Cost, Green-Mode PWM Controller for Flyback Converters Feedback Input Section Symbol Parameter AV VFB-OPEN VFB-N VFB-G SG =FB Input to Current Comparator Attenuation Test Condition Min. Typ. Max. Unit 4.5 2/5 5.0 2.85 2.20 5.5 V/V V V V Hz/mV 5 KΩ ZFB Input Impedance FB Output High Voltage Green-Mode Entry FB Voltage Green-Mode Ending FB Voltage Green-Mode Modulation Slope == = = RI=95kΩ 75 Current-Sense Section Symbol Parameter ZSENSE Input Impedance tPD VSTHFL VSTHVA tLEB DCYSAW Delay to Output Flat Threshold Voltage for Current Limit Valley Threshold Voltage for Current Limit Leading-edge Blanking Time Duty Cycle of SAW Limit Test Condition Min. Typ. Max. Unit Max. Duty Cycle 10 kΩ 0.75 250 60 0.96 0.80 300 45 100 0.85 350 ns V V ns % Oscillator Section Symbol Parameter FOSC Frequency FOSC-G FDV FDT Green-Mode Frequency Frequency Variation vs. VDD Deviation Frequency Variation vs. Temperature Deviation Test Condition Min. Typ. Max. Unit RI=95kΩ 65 70 75 kHz RI=95kΩ VDD=13.5V to 22V 0 22 0.02 2.00 kHz % TA= -20 to 85°C 2 % Output Section Symbol Parameter DCYMAX Maximum Duty Cycle VGATE-L Output Voltage Low VGATE-H Output Voltage High tR Rising Time tF Falling Time VGATE-CLAMP Output Clamp Voltage Test Condition Min. Typ. Max. Unit 70 75 80 % V VDD=15V, Io20mA VDD=13.5V, Io-20mA 8 1.5 V VDD=15V, CL1nF 150 200 250 ns VDD=15V, CL1nF 35 55 75 ns VDD22V 16 17 18 V © System General Corp.

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Product Specification SG6858 Low-Cost, Green-Mode PWM Controller for Flyback Converters TYPICAL CHARACTERISTICS Turn-On Threashold Voltage (VDD-ON) vsTemperature17.512.512.1 Turn-off Threshold Voltage (VDD-OFF) vsTemperature17.0VDD-ON (V)VDD-OFF (V)-40-25-10520355065809511012511.711.310.910.5-40-25-10520355065809511012516.516.015.5Temperature (℃)Temperature (℃)Startup Current(IDD-ST) vs Temperature20 3.5Operating Supply Current (IDD-OP) vs Temperature153.0IDD-ST (uA)10IDD-OP(mA)2.552.0VDD=15V 0-40-25-1052035506580951101251.5-40-25-1052035506580VDD=15V 95110125Temperature (℃)Temperature (℃) Frequency (FOSC) vs Temperature7573716967 8078Maximum Duty Cycle (DCYMAX) vs TemperatureDCYMAX(%)FOSC(KHz)767472VDD=15V 65-40-25-10520355065809511012570-40-25-1052035506580VDD=15V 95110125Temperature (℃)Temperature (℃) © System General Corp.

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Product Specification SG6858 Green-Mode Ending FB Voltage (VFB-G) vsTemperature2.502.40 Low-Cost, Green-Mode PWM Controller for Flyback Converters Green-Mode Entry FB Voltage(VFB-N) vsTemperature3.23.13.02.92.82.72.62.5-40-25-105203550658095110125 VFB-G(V)VFB-N(V)2.302.202.102.001.90-40-25-105203550658095110125VDD=15V VDD=15V Temperature (℃)Temperature (℃)Leading-Edge Blanking Time (tLEB) vs Temperature350330310290270 3.53.0Operation Current (IDD-OP) vs VDD VoltageIDD-OP (mA)tLEB (nsec)2.52.0VDD=15V 250-40-25-1052035506580951101251.512131415161718192021222324Temperature (℃)VDD Voltage (V) © System General Corp.

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Product Specification

SG6858

Low-Cost, Green-Mode PWM Controller for Flyback Converters OPERATION DESCRIPTION

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.

frequency. The relationship between RI and the switching frequency is:

fPWM =

6650RI (kΩ)

(kHz)

Start-up Current

The start-up current is only 10µA, which allows a start-up resistor with a high resistance and a low-wattage to supply the start-up power for the controller. A 1.5MΩ, 0.25W, start-up resistor and a 10µF/25V VDD hold-up capacitor are sufficient for an AC-to-DC power adapter with a wide input range (100VAC to 240VAC).

(1)

Leading-Edge Blanking

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 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 cannot switch off the gate driver.

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.

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.

This propagation delay introduces 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 2VAC).

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 SG6858 can meet even the strictest regulations regarding standby power consumption.

Oscillator Operation

A resistor connected from the RI pin to ground generates a constant current source 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 the switching frequency. A 95kΩ resistor, RI, results in a 50µA constant current, II, and a 70kHz switching

© System General Corp.

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Product Specification

SG6858

Low-Cost, Green-Mode PWM Controller for Flyback Converters Under-Voltage Lockout (UVLO)

The turn-on and turn-off thresholds of the SG6858 are fixed internally at 16.5V/11.5V. During start-up, the hold-up capacitor must be charged to 16.5V through the start-up resistor to enable SG6858. 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 start-up process. This UVLO hysteresis window ensures that hold-up capacitor is 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 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:

0.36×DutyDuty(max.)

(2)

VDD Over-Voltage Protection

VDD over-voltage protection has been built in to prevent damage due to over-voltage conditions. When the voltage VDD exceeds the internal threshold due to abnormal conditions, PWM output is turned off until the VDD voltage drops below the UVLO, then starts up again. Over-voltage conditions are usually caused by open-feedback loops.

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 SG6858, and increasing the power MOS gate resistance improves performance.

Gate Output

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.

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Product Specification SG6858 Low-Cost, Green-Mode PWM Controller for Flyback Converters REFERENCE CIRCUIT 1LF1BD1CX124R1C1C2R531NR2R4109D1U1GNDFBRIGATEVDDSENSE285Q1373,42GND2R10C7C8D5C91T11,22D411L221L12C3R3VO123C6R96R71R15C11R6R8C41D22R11R134U2R1432C103U31R122CY1 BOM Reference Component BD1 BD 1A/500V CX1 (Optional) XC 0.1µF CY1 (Optional) YC 1000pF/400V (Y1) C1 C2 C3 C4 C6 C8 C9 C10 C11 D1 D2 D4 CC 10nF/500V EC 10µF/400V 105℃ CC 1000pF/500V EC 10µF/50V CC 1000pF 0805 EC 470µF/10V 105℃ EC 220µF/10V 105℃ CC 2200pF 0805 N.C. Diode FRI07 Diode FR102 Diode SB360 Reference L2 Q1 R1,R2 R4,R3 R5 R6 R7 R8 R9 R11 R12 R13 R14 R15 T1 U1 U2 U3 C7 (Optional) CC 1000pF/100V 1206 R10 (Optional) R 10Ω 1206 R 100Ω 1/8W R 33KΩ 0805 R 33KΩ 1/8W R 4.7KΩ 0805 R 0Ω 0805 Transformer EE-16 IC SG6858 IC PC817 IC TL431 D5 (Optional) ZD 6.8V 0.5W F1 R 1Ω/0.5W L1 Inductor 20mH 6x8mm © System General Corp.

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1Component Inductor 10µH 6mm MOSFET 1A/600V R 750KΩ 1206 R 47KΩ 1206 R 47Ω 1206 R 4.7Ω 1206 R 100Ω 0805 R 10Ω 1206 R 100KΩ 0805 www.sg.com.tw • www.fairchildsemi.com

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Product Specification SG6858 Low-Cost, Green-Mode PWM Controller for Flyback Converters PACKAGE INFORMATION 8 PINS - DIP (D) D85Θ¢XE1EeB14A1A2Lb1beDimensions Symbol Millimeters Inches Min. Typ. Max. Min. Typ. Max. A 5.334 0.210 A1 0.381 0.015 A2 3.175 3.302 3.429 0.125 0.130 0.135 b 1.524 0.060 b1 0.457 0.018 D E1 L eB θ˚ 9.017 9.271 10.160 0.355 0.365 0.400 6.223 6.350 6.477 0.245 0.250 0.255 2.921 3.302 3.810 0.115 0.130 0.150 8.509 9.017 9.525 0.335 0.355 0.375 0˚ 7˚ 15˚ 0˚ 7˚ 15˚ E 7.620 0.300 e 2.0 0.100 © System General Corp.

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Product Specification SG6858 Low-Cost, Green-Mode PWM Controller for Flyback Converters 6 PINS - SOT (T) DbDetail AE1E1e1e3c1RA2ALA1L11Detail ADimensions Symbol Millimeters Inches Min. Typ. Max. Min. Typ. Max. A 1.45 0.057 A1 0.15 0.006 A2 0.90 1.15 1.30 0.036 0.045 0.051 b 0.30 0.50 0.011 0.020 c 0.08 0.22 0.003 0.009 D 2.90 0.114 E 2.80 0.110 E1 1.60 0.063 e 0.95 0.037 e1 1.90 0.075 L 0.30 0.45 0.60 0.020 0.018 0.024 L1 0.60 0.024 L2 0.25 0.010 R 0.10 0.004 R1 0.10 0.25 0.004 8° 0° 4° 0.010 8° θ° θ1° 0° 4° 5° 10° 15° 5° 10° 15° © System General Corp.

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Product Specification

SG6858

Low-Cost, Green-Mode PWM Controller for Flyback Converters

© System General Corp.

Version 1.2.1 (IAO33.0045.B2)

- 13 -

www.sg.com.tw • www.fairchildsemi.com

September 25, 2007