SG6840 S G6 8 40 D at a S h e et DESCRIPTION FEATURES OVERVIEW This ●Green-mode PWM to support “Blue Angle”Norm high-integrated PWM controller provides several special enhancements to satisfy the ●Low start up current 30uA needs for low power standby and protection ●Low operation current 3mA features. In standby mode, PWM frequency ●Leading-edge blanking reduction is used to lower the power consump- ●Built-in synchronized slope compensation tion and support a stable output voltage. Due to ●Totem pole output includes soft driving Bi-CMOS process, the SG6840 reduces start- ●Constant output power up and operation current to achieve a higher efficiency power conversion. Start-up current ●Current mode operation has been reduced to 30uA typical and operating ●Cycle-by-cycle current limiting current has been shrunk to 3mA. The SG6840 ●Under voltage lockout (UVLO) is a fixed frequency PWM controller in normal ●Short circuit protection operation; its patented green-mode function will ●Programmable over-temperature protection decrease the PWM frequency in response to ●Few external components & low cost solution the decrease of the load. This green function dramatically reduces the power loss in no load and light load conditions that assist the power supply to meet the power conservation requirement. The proprietary synchronized slope compensation ensures the stability of the current PIN CONFIGURATION loop for continuous-mode operation. Built-in line -voltage compensation maintains an identical output power for a wide input range. An NTC thermistor is applied to sense the temperature for over-temperature protection. The SG6840 is available in 8-pin DIP and SO packages. APPLICATIONS General-purpose switching mode power supplies and flyback power converters, and ●Power Adapter ●Open-frame SMPS ●Battery Charger Adapter - 1 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 PIN DESCRIPTIONS Name Pin No. Type Function Supply Power supply. VDD 7 VIN 3 The start-up current input. A start-up resistor is connected from the Analog inline-input to this pin, such as 1.5MΩ for off-line converter. Adjust the put start-up resistor to vary the line voltage compensation for constant FB 2 Analog in- Feedback. The FB pin provides the information of the regulation, it put effects to the internal PWM comparator to control the duty cycle. Current sense. It senses the voltage developed on a sensed resistor. Analog in- When it reaches the internal threshold, the PWM output is disabled. put Therefore, the over-current protection is realized. Besides, the current information is providing for the current mode control. For over-temperature protection. A constant current is output. Analog in- An NTC thermistor is connected from this pin to ground to sense the put/output temperature. When the voltage in this pin is lower than the limit, which will enable the over-temperature protection. Sense 6 RT 5 Gate 8 Driver out- The totem-pole output driver to drive the power MOSFET. Ri 4 Program- Reference setting. Connect a resistor to ground to generate a con- GND 1 Supply Ground. BLOCK DIAGRAM Ri 4 VDD Soft ON/OFF Driver 0.8V VIN Gate 6 Sense 2 FB + 3 _AI Internal BIAS VDD 8 + 7 UVLO Q S OSC Green Mode Controller R _ 16V/10V Comp Slope Compensation 5V I RT RT + 5 _ Comp 0.7V 1 GND - 2 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 ABSOLUTE MAXIMUM RATINGS Symbol Parameter Value Unit VDD DC Supply Voltage – note 1 20 V Iout Gate Output Current 500 mA VFB Input Voltage to FB Pin -0.3 to 7 V V VSense Input Voltage to Sense Pin -0.3 to 7V V Pd Power Dissipation 1 W TJ Operating Junction Temperature 150 。C TA Operating Ambient Temperature -25 to 85 。C Tstg Storage Temperature Range -55 to +150 。C Note: All voltage values, except differential voltage, are with respect to network ground terminal. ELECTRCIAL CHARACTERISTICS(VDD=15V, TA=25) Feedback Input Section Symbol Av Parameter Input-voltage to current-sense attenuation Test Condition Min. 1/4.5 Typ. 1/5 3 4.5 Max. 1/5.5 Unit V/V Zfb Input impedance 6 KΩ Ifb Bias current 2 mA Voz Input voltage for zero duty cycle 1.2 V Typ. Max. Unit 8 12 16 KΩ 150 200 nS 0.8 0.85 0.9 V -0.09 -0.15 -0.21 V Min. 60 Typ. 65 10 Current Sense Section Symbol Parameter Zcs Test Condition Input impedance TPD Delay to Output Vth Threshold voltage for current limit The change of threshold voltage versus the input current of the Vin ∆Vth @ Iin Iin = 220 uA Min. Oscillator Section Symbol Fosc Fosc-green Parameter Frequency Frequency in green mode Vg Green mode voltage (Vg = Vfb - Vd) Normal mode voltage (Vn = Vfb - Vd) Vn = 4 V for maximum duty cycle Vn Test Condition Ri=26KOhms Ri=26KOhms Max. 70 15 1.3 Unit KHz KHz V 1.7 2 2.3 50 80 120 V Sg Slope for green mode modulation Ri=26KOhms Fdv Frequency variation versus VDD deviation Frequency variation versus Temp. deviation VDD=10 to 20V 5 Hz/ mV % TA=-25 to 85 ℃ 5 % Fdt - 3 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 PWM Section Symbol DC (MAX) Parameter Maximum Duty Cycle Test Condition Min. 75 Typ. 80 Max. 90 Unit % DC (MIN) Minimum Duty Cycle - - 0 % Bnk Leading edge blanking time 200 270 350 nsec Output Section Symbol Vol Parameter Output Voltage Low Test Condition VDD= 12V, Io = 150mA Min. Typ. Max. 1.5 Unit V Voh Output Voltage High VDD= 12V, Io = 50mA 8V tr tf Rising Time Falling Time VDD=13V, CL=1nF VDD=13V, CL=1nF 150 30 250 50 350 90 NS NS Min. 15 Typ. 16 Max. 17 Unit V 9 10 11 V Test Condition Ri=26KOhms Min. 92 0.665 Typ. 100 0.7 Max. 108 0.735 Unit uA V Test Condition Min. Typ. 30 Max. 40 Unit uA V Under-voltage Lockout Section Symbol VTH(ON) Parameter Start Threshold Voltage VDD(min) Min. Operating Voltage Test Condition Over-temperature Protection Section Symbol Irt Vtov Parameter Output current of pin RT Threshold voltage for over-temperature protection Total Standby Current Section Symbol IDD ST Parameter Start-up Current IDD OP Operating Supply Current - - 3 5 mA - 4 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 Start-up Current (IDD ST) vs VDD Voltage Start-up Current (IDD ST) vs Tem perature 35 Start-up Current (uA) Start-up Current (uA) 25.5 25.0 24.5 24.0 23.5 23.0 22.5 22.0 30 25 20 15 10 5 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 0 2 4 6 TEMPERATURE (℃ ) 8 10 12 14 16 VDD VOLTAGE (V) FB Voltage vs Frequency Frequency in green m ode (Fosc-green) vs Tem perature 60 10.55 Fosc-green (KHz) Frequency (KHz) 70 50 40 30 20 10 0 10.50 10.45 10.40 10.35 10.30 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 -40 -25 -10 5 FB VOLTAGE (V) PWM Oscillator Frequency (Fosc) vs Tem perature Max. Duty Cycle (%) Fosc (KHz) 64.3 64.2 64.1 64.0 63.9 63.8 63.7 -25 -10 5 20 35 50 65 35 50 65 80 95 110 125 Maxim um Duty Cycle DC( MAX.)vs Tem perature 64.4 -40 20 TEMPERATURE (℃ ) 80 95 110 84.80 84.70 84.60 84.50 84.40 84.30 84.20 -40 125 TEMPERATURE (℃ ) -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (℃ ) - 5 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 Start Threshold Voltage (V TH(ON)) vs Tem perature 16.60 10.20 10.15 10.10 10.05 10.00 9.95 9.90 9.85 9.80 9.75 9.70 16.55 VTH(ON) (V) VDD(min) (V) Min. Operating Voltage (V DD(min)) vs Tem perature 16.50 16.45 16.40 16.35 16.30 16.25 16.20 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 TEMPERATURE (℃ ) 20 35 50 65 80 95 110 125 110 125 TEMPERATURE (℃ ) Output Current of pin RT (IRT) vs Tem perature RT Voltage vs Ton 12 101.5 10 101.0 8 I RT (uA) Ton (uS) 14 6 4 2 100.5 100.0 99.5 99.0 0 98.5 -2 0.620 0.628 0.636 0.644 0.652 -40 0.660 -25 -10 5 20 35 50 65 80 95 TEMPERATURE (℃ ) RT VOLTAGE (V) V OTP, STOP vs Tem perature 0.63 VOTP, STOP (V) 0.62 0.62 0.61 0.61 0.60 0.60 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (℃ ) - 6 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 OPERATION DESCRIPTION Current sensing and PWM current limiting Start-up Current SG6840 consists of two feedback loops: voltage loop and current loop, to control the load regulation. SG6840’s current sense input is designed for the current-mode control. A current-to-voltage conversion is done externally through a current-sense resistor Rs. Under normal operation, the FB voltage VFB controls the peak voltage across the sense resistor Rs, hence the PWM duty cycle, as follows: Typical start-up current is only 30uA This ultra low start-up current allows users to use a high resistance, and lowwattage, start-up resistor to supply the start-up power required by SG6840. Take a wide input-range (100VAC~240VAC) of AC-to-DC power adapter as an example, an 1.5 MΩ, 0.25W, start-up resistor and a 10uF/25V VDD hold-up Ipk = (VFB – 1.4) / 5Rs; Operating Current where Operating current has been reduced to 3mA. The low operating current enables a better efficiency and reduces the VFB is the voltage on pin FB When the DC output voltage of secondary side decreases due to heavy load conditions, the FB voltage VFB will increase such that the PWM duty cycle increases to regulate the output voltage of secondary side back to its normal voltage. The inverting input to SG6840’s current-sense comparator is internally clamped to a variable voltage around 0.85V (note: see Constant Output Power Limit section). The current limiting occurs if the voltage of SENSE pin reaches this 0.85V threshold value, such as Ipk (max) = 0.85V/Rs. The value of sense resistor Rs decides the maximum power limit. Larger Rs, whose Ipk is smaller, results in a smaller power limit Green Mode Operation The patented green-mode function provides an off-time modulation to reduce the switching frequency in the light load and no load conditions. The feedback voltage, which is derived from the voltage feedback loop, is taken as the reference. Once the feedback voltage is lower than the threshold voltage, switching frequency will linearly decrease until the minimum green mode frequency around 10kHz (Ri =26kΩ). We can find that all of the losses are in proportional to the switching frequency, such as the switching loss of the transistor, the core loss of the transformer and inductors, and the power loss of the snubber, etc. The off-time modulation in the PWM controller can reduce the power consumption of the power supply in light load and no load conditions. In normal load and high load conditions, the PWM frequency is at its maximum frequency around 65kHz (Ri =26kΩ) and not affected by the off-time modulation. Leading Edge Blanking Each time when the power MOSFET is switched on, a leading spike is generated due to parasitic capacitance. To avoid premature termination of the switching pulse, this leading edge spike is blanked out with a time constant 270 nsec. During this time period, the current-limit comparator is disabled and cannot switch off the gate drive regardless how big the SENSE voltage is. Oscillator Operation An external resistor Ri determines the PWM oscillation frequency. A 26kΩ resistor Ri creates a 50uA constant current Ii and generates 65kHz switching frequency. Under-voltage lockout (UVLO) The UVLO Under-Voltage Lockout (UVLO) function ensures the supply voltage VDD for SG6840 is adequate to fully function before enabling the output stage. The turn-on and turn-off threshold voltages are fixed internally at 16V/10V. The hysteresis voltage between turn-on and turn-off prevents VDD from being unstable during power on/off sequencing. Start-up current is typically 30uA for efficient bootstrapping from the rectified input for an off-line converter. During the normal operation, VDD is developed from an auxiliary winding of the transformer. At the moment of start-up, VDD hold-up capacitor CIN must be charged up to 16V through the start-up resistor RIN before enabling the output switch. With an ultra small start-up current of 30uA, RIN can be as large as 1.5 MΩ and still be able to charge up the hold-up capacitor CIN even when VAC = 90Vrms. Power dissipation of this large resistance RIN would then be less than 70mW (0.07W) even under high line (VAC = Ii (mA) = 1.3V / Ri (kΩ); fPWM = 1690 RI (kΩ ) (kHz ) (1) - 7 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 Gate Output / Soft Driving Noise immunity The SG6840 BiCMOS output stage is a fast totem pole gate driver, which is designed to avoid cross conduction current. This minimizes heat dissipation, increases efficiency and enhances reliability. The output driver is clamped by an internal 18V Zener diode in order to improve the control of the power MOSFET transistors and protect them against undesirable gate over-voltage. By controlling the rising time of the switch-on waveform and falling shape of the switch-off waveform, the output stage is optimized to reduce switching noise, improve EMI, and to provide a stable MOSFET gate drive. Noise on the current sense or control signal can cause significant pulse width jitter, particularly with the continuousmode operation. While slope compensation helps alleviate this problem. Note that the SG6840 has a single ground pin. High sink current in the output therefore cannot be returned separately. Good high frequency or RF layout practices should be followed. Avoid long PCB traces and component leads. Locate components such as Ri, Rt and VDD capacitor near to the SG6840. The noise, which often causes the problem, is caused by the output (pin 8) being pulled below ground at turn-off by external parasitic. This is particularly true when driving MOSFET. A resistor (10 ~ 20 ohms) series connected from the output (pin 8) to the gate of MOSFET will prevent such output noise. Built-in Slope Compensation Current mode control regulates the peak transformer/inductor current via the current control loop. In a continuous mode operation, the current is the average current, and composed of both AC and DC components. Since the output is proportional to the average, not the peak current, this causes oscillation when input voltage is changed. Adding the slope compensation to the current loop (reduce the current loop gain) to correct the problem is a simple approach. The SG6840 inserts a synchronized 0.33V positive-going ramp at every switching cycle to stabilize the current loop. Vs-comp = 0.33V. Constant Output Power Limit Every time when the SENSE voltage, across the sense resistor Rs, is larger than the threshold voltage around 0.85V, the output GATE drive is turned off after a small propagation delay tD. Since the propagation delay is constant regardless the input line voltage VIN, the output power would not be equal for the wide input voltage VIN of 90Vrms to 265Vrms. To compensate the different output power limit between high line voltage and low line voltage, the internal threshold voltage is adjusted dependent on the input line voltage VIN through the VIN pin. The threshold voltage is decreased from 0.85V to a smaller voltage when input line voltage VIN increases. Smaller threshold voltage, at higher input line voltage, forces the output GATE drive to terminate earlier, thus reduce the total PWM turn-on time and make the output power equal to that of low input line voltage. Thermal Protection A constant current IRT is output from pin RT. The resistor in pin Ri decides the current IRT. IRT = 2 x (1.3V / Ri); An NTC thermistor Rntc in series with a resistor Ra can be connected from pin RT to ground. The over-temperature - 8 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 APPLICATION CIRCUIT BOM Reference Component Reference BD1 BD 1A/600V Q2 MOS 2A/600V C1 XC 0.22u C2 EC 0.1u 250V R3 R 47ohm 1/4W YC 222p R4 R 22ohm 1/4W C4 EC 68u/400V R5 R 4.7Kohm 1/4W C5 CC 102p/1KV R6 R 0.5ohm 1W C8 EC 1200u/16V R8,R12 C9 EC 680u/16V R9 R 20Kohm 1/8W 1% C10 EC 10u/25V R10 R 100ohm 1/8W D1 LED D3 ZD 12V T1 Transformer EI28 F1 FUSE 2A/250V U1 IC SG6840 L1 UU10.5 U2 IC 4N35D L2 L04 U3 IC TL431 Q1 DIODE VZ1 VZ 9G C3,C6,C7 R1,R2 Component THER1 R 470Kohm 1/4W R 510Kohm 1/4W Thermistor SCK054 - 9 2002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 MECHANICAL DIMENSIONS 8 PINS – PLASTIC DIP (D) 8 5 E 1 4 D b A A1 A2 b2 e Symbol Min. A b1 Millimeter Typ. 3.4 A1 A2 b b1 b2 d d Max. Min. d H Inch Typ. 0.134 4.5 3.0 0.4 0.25 0∘ 0.177 0.118 1.5 0.5 0.3 0.6 0.4 15∘ 0.016 0.010 0∘ 0.059 0.020 0.012 D 9.3 0.366 E e H 6.5 2.54 7.6 0.256 0.100 0.299 2.29 Max. 2.79 0.090 0.024 0.016 15∘ 0.110 -102002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification SG6840 MECHANICAL DIMENSIONS 8 PINS – PLASTIC SMD (S) Dimension: b 8 5 E H d L 4 1 Detail D A2 A c e A1 L1 See Detail Symbol A A1 A2 b c d D E e H L L1 Y Min. 1.35 0.10 1.30 0.33 0.19 0∘ 4.80 3.80 5.80 0.40 - Millimeter Typ. 1.63 0.15 1.40 0.41 4.90 3.90 1.27 6.00 0.64 1.07 - Max. 1.75 0.25 1.50 0.51 0.25 8∘ 5.00 4.00 6.20 1.27 0.10 Min. 0.053 0.004 0.051 0.013 0.007 0∘ 0.189 0.150 0.228 0.016 - Inch Typ. 0.064 0.006 0.055 0.016 0.193 0.154 0.050 0.236 0.025 0.042 - Max. 0.069 0.010 0.059 0.020 0.010 8∘ 0.197 0.157 0.244 0.050 0.004 -112002 System General Corporation Ver1.0 http://www.sg.com.tw High-integrated Green Mode PWM Controller - SG6840 Product Specification