FAN6862R

FAN6862R/L — Highly Integrated Green-Mode PWM Controller January 2010 FAN6862R / FAN6862L Highly Integrated Green-Mode PWM Controller Features Low Startup Current: 8µA Low Operating Current in Green Mode: 3mA Peak-Current-Mode Operation with Cycle-by-Cycle Current Limiting PWM Frequency Continuously Decreasing with Burst Mode at Light Loads VDD Over-Voltage Protection (OVP) Constant Output Power Limit (Full AC Input Range) Over-Temperature Protection (OTP) Fixed PWM Frequency (65KHz) with Frequency Hopping Feedback Open-Loop Protection with 56ms Delay Soft Start Time: 5ms 400mA Driving Capability Description A highly integrated PWM controller, FAN6862R/L provides several features to enhance the performance of flyback converters. To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency under light-load conditions. Under zero-load conditions, the power supply enters burst mode, which completely shuts off PWM output. Output restarts just before the supply voltage drops below the UVLO lower limit. This green-mode function enables power supplies to meet international power conservation requirements. The FAN6862R/L is designed for SMPS and integrates a frequency-hopping function that helps reduce EMI emission of a power supply with minimum line filters. The built-in synchronized slope compensation is proprietary sawtooth compensation for constant output power limit over universal AC input range. The gate output is clamped at 18V to protect the external MOSFET from over-voltage damage. Other protection functions include VDD over-voltage protection, over-temperature protection, and overload protection. For over-temperature protection, an external NTC thermistor can be applied to sense the ambient temperature. When OVP, OTP, or OLP is activated, an internal protection circuit switches off the controller. Applications General-purpose switch-mode power supplies and flyback power converters, including: Power Adapters Open-Frame SMPS SMPS with Surge-Current Output, such as for Printers, Scanners, and Motor Drivers Part Number FAN6862LTY OVP Latch OTP Latch OLP Latch FAN6862RTY Auto Restart Auto Restart Auto Restart Ordering Information Part Number FAN6862RTY FAN6862LTY Operating Temperature Range -40 to +105°C -40 to +105°C Eco Status Green Green Package 6-Pin SSOT-6 6-Pin SSOT-6 Packing Method Tape & Reel Tape & Reel For Fairchild’s definition of Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html. © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com FAN6862R/L — Highly Integrated Green-Mode PWM Controller Typical Application Figure 1. Typical Application Block Diagram Figure 2. Block Diagram © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 2 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Marking Information •••• ABxTT --Figure 3. Top Mark ABx: TT: : _ _ _: ABA: FAN6862LTY ABC: FAN6862RTY Wafer Lot Code Year Code Week Code Pin Configuration Figure 4. Pin Assignments Pin Definitions Pin # Name 1 2 GND FB Function Ground Feedback Description Ground The FB pin provides the output voltage regulation signal. It provides feedback to the internal PWM comparator for control of the duty cycle. This pin also provide for OLP: if VFB is larger than the trigger level and remains for a long time, the controller stops and restarts. 3 RT An external NTC thermistor is connected from this pin to GND for over-temperature Temperature protection. The impedance of the NTC decreases at high temperatures. Once the Detection voltage of the RT pin drops below a threshold, PWM output is disabled. Current Sense This pin senses the voltage across a resistor. When the voltage reaches the internal threshold, PWM output is disabled. This activates over-current protection. This pin also provides current amplitude information for current-mode control. 4 5 6 SENSE VDD GATE Power Supply Power supply Driver Output The totem-pole output driver for driving the power MOSFET. © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 3 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Absolute Maximum Ratings 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 VDD VL PD ΘJC TJ TSTG TL ESD Supply Voltage Parameter Input Voltage to FB, SENSE, RT Pin Power Dissipation at TA51% Duty=0% Duty=DCYMAX 360 0.5 0.44 0.273 5 VFB>VFB-N VFB≥VFB-N VFB=VFB-G VFB≥VFB-N VFB=VFB-G 62 65 ±4.2 ±2.9 4.4 11.5 22.5 2.5 2.1 1.7 VDD=11.5V to 20V TA= -40 to +105°C 0 0.02 2.00 2 ms ms kHz V V V % % 68 kHz Oscillator Section fOSC thop-1 thop-3 fOSC-G VFB-N VFB-G VFB-ZDC fDV fDT Normal PWM Frequency Hopping Range Hopping Range Hopping Period 1 Hopping Period 3 Green Mode Minimum Frequency FB Threshold Voltage For Frequency Reduction FB Voltage at fOSC-G FB Threshold Voltage for Zero Duty Frequency Variation vs. VDD Deviation Frequency Variation vs. Temperature Deviation Continued on the following page… © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 5 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Electrical Characteristics (Continued) VDD = 15V and TA = 25°C unless otherwise noted. Symbol PWM Output Section DCYMAX VOL VOH tR tF VCLAMP IRT VOTP tDOTP VOTP2 tDOTP2 Parameter Maximum Duty Cycle Output Voltage Low Output Voltage High Rising Time Falling Time Gate Output Clamping Voltage Output Current of RT Pin Threshold Voltage for Over-Temperature Protection Over-Temperature Debounce Time 2 Threshold Voltage for OverTemperature Protection 2 nd nd Test Condition Min. Typ. 70 Max. Unit % VDD=15V, IO=50mA VDD=8V, IO=50mA CL=1nF CL=1nF VDD=20V 15.0 6 150 35 16.5 100 TA=25°C VFB=VFB-N VFB=VFB-G TA=25°C 0.60 0.97 1.02 17 51 0.70 100 1.5 200 18.0 V V ns ns V μA Over-Temperature Protection (OTP) Section 1.07 V ms 0.75 V μs Over-Temperature Debounce Time © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 6 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Typical Performance Characteristics 17 9.5 16.6 9.1 VDD-OFF (V) -40 -30 -15 0 25 50 75 85 100 125 VDD-ON (V) 16.2 8.7 15.8 8.3 15.4 7.9 15 7.5 -40 -30 -15 0 25 50 75 85 100 125 Temperature (ºC) Temperature (ºC) Figure 5. Turn-On Threshold Voltage (VDD-ON) vs. Temperature Figure 6. Turn-Off Threshold Voltage (VDD-OFF) vs. Temperature 4.5 26 4.1 25.6 IDD-OP (mA) 3.7 VDD-OVP (V) -40 -30 -15 0 25 50 75 85 100 125 25.2 3.3 24.8 2.9 24.4 2.5 24 -40 -30 -15 0 25 50 75 85 100 125 Temperature (ºC) Temperature (ºC) Figure 7. Operating Current (IDD-OP) vs. Temperature Figure 8. VDD Over-Voltage Protection (VDD-OVP) vs. Temperature 68 67 66 2.7 2.6 fOSC (KHz) VFB-N (V) 2.5 65 64 63 62 -40 -30 -15 0 25 50 75 85 100 125 2.4 2.3 2.2 -40 -30 -15 0 25 50 75 85 100 125 Temperature (ºC) Temperature (ºC) Figure 9. Center Frequency (fOSC) vs. Temperature Figure 10. FB Threshold Voltage for Frequency Reduction (VFB-N) vs. Temperature © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 7 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Typical Performance Characteristics (Continued) 2.3 4.9 4.8 4.7 4.6 4.5 4.4 4.3 -40 -30 -15 0 25 50 75 85 100 125 -40 -30 -15 0 25 50 75 85 100 125 2.2 2.1 2 1.9 1.8 Temperature (ºC) VFB-OLP (V) VFB-G (V) Temperature (ºC) Figure 11. FB Voltage at fOSC-G (VFB-G) vs. Temperature Figure 12. Threshold Voltage for Open-Loop Protection (VFB-OLP) vs. Temperature 59 58 57 56 55 54 53 -40 -30 -15 0 25 50 75 85 100 125 0.6 0.56 tD-OLP (mS) VSTHFL (V) 0.52 0.48 0.44 0.4 -40 -30 -15 0 25 50 75 85 100 125 Temperature (ºC) Temperature (ºC) Figure 13. Open-Loop Protection Delay Time (tD-OLP) vs. Temperature Figure 14. Flat Threshold Voltage for Current Limit (VSTHFL) vs. Temperature 0.55 7 0.51 6 0.47 tSOFT-START (mS) VSTHVA (V) 5 0.43 4 0.39 3 0.35 -40 -30 -15 0 25 50 75 85 100 125 2 -40 -30 -15 0 25 50 75 85 100 125 Temperature (ºC) Temperature (ºC) Figure 15. Valley Threshold Voltage for Current Limit (VSTHVA) vs. Temperature Figure 16. Period during Startup (tSOFT-START) vs. Temperature © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 8 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Typical Performance Characteristics (Continued) 72 180 71 160 DCYMAX (%) 69 tR (nS) -40 -30 -15 0 25 50 75 85 100 125 70 140 120 68 100 67 80 -40 -30 -15 0 25 50 75 85 100 125 Temperature (ºC) Temperature (ºC) Figure 17. Maximum Duty Cycle (DCYMAX) vs. Temperature Figure 18. Rising Time (tR) vs. Temperature 70 120 60 112 40 IRT (μA) -40 -30 -15 0 25 50 75 85 100 125 tF (nS) 50 104 96 30 88 20 80 -40 -30 -15 0 25 50 75 85 100 125 Temperature (ºC) Temperature (ºC) Figure 19. Falling Time (tF) vs. Temperature Figure 20. Output Current of RT Pin (IRT) vs. Temperature © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 9 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Operation Description Startup Operation Figure 21 shows a typical startup circuit and transformer auxiliary winding for a typical application. Before FAN6862R/L begins switching operation, it consumes only startup current (typically 8μA) and the current supplied through the startup resistor charges the VDD capacitor (CDD). When VDD reaches the turn-on voltage of 16V (VDD-ON), FAN6862R/L begins switching and the current consumed increases to 3mA. Then the power required is supplied from the transformer auxiliary winding. The large hysteresis of VDD (8.5V) provides more holdup time, which allows using a small capacitor for VDD. The startup resistor is typically connected to AC line for a fast reset of latch protection. Frequency PWM Frequency +4.2kHz 65kHz -4.2kHz +2.9kHz 22.5kHz -2.9kHz VFB-ZDC VFB -G VFB -N VFB Figure 22. PWM Frequency Vo VFB VFB.ZDC (1.7V) Ids Figure 21. Startup Circuit Switching Disabled Switching Disabled Figure 23. Burst-Mode Operation Green-Mode Operation The FAN6862R/L uses feedback voltage (VFB) as an indicator of the output load and modulates the PWM frequency, as shown in Figure 22, such that the switching frequency decreases as load decreases. In heavy-load conditions, the switching frequency is 65KHz. Once VFB decreases below VFB-N (2.5V), the PWM frequency starts to linearly decrease from 65KHz to 22.5kHz to reduce the switching losses. As VFB decreases below VFB-G (2.1V), the switching frequency is fixed at 22.5kHz and FAN6862R/L enters “deep” green mode, where the operating current decreases to 2.5mA (maximum), further reducing the standby power consumption. As VFB decreases below VFB-ZDC (1.7V), FAN6862R/L enters burst-mode operation. When VFB drops below VFB-ZDC, switching stops and the output voltage starts to drop, which causes the feedback voltage to rise. Once VFB rises above VFB-ZDC, switching resumes. Burst mode alternately enables and disables switching, thereby reducing switching loss in standby mode, as shown in Figure 23. Frequency Hopping EMI reduction is accomplished by frequency hopping, which spreads the energy over a wider frequency range than the bandwidth measured by the EMI test equipment. An internal frequency hopping circuit changes the switching frequency between 60.8kHz and 69.2kHz with a period of 4.4ms, as shown in Figure 24. Figure 24. Frequency Hopping © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 10 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Protections Self-protective functions include VDD Over-Voltage Protection (OVP), Open-Loop / Overload Protection (OLP), Over-Current Protection (OCP), Short-Circuit Protection, and Over-Temperature Protection (OTP). FAN6862R uses auto-restart mode protections and FAN6862L uses latch-mode protections. Auto-Restart Mode Protection: Once a fault condition is detected, switching is terminated and the MOSFET remains off. This causes VDD to fall because no more power is delivered from auxiliary winding. When VDD falls to VDD-OFF (8.5V), the protection is reset and the operating current reduces to startup current, which causes VDD to rise. FAN6862R resumes normal operation when VDD reaches VDD-ON (16V). In this manner, the auto-restart can alternately enable and disable the switching of the MOSFET until the fault condition is eliminated (see Figure 25). Latch-Mode Protection: Once this protection is triggered, switching is terminated and the MOSFET remains off. The latch is reset only when VDD is discharged below 4V by unplugging AC power line. VDS Power On Protection Triggers Fault Removed Open-Loop / Overload Protection (OLP) W hen the upper branch of the voltage divider for the shunt regulator (KA431 shown) is broken, as shown in Figure 26, no current flows through the opto-coupler transistor, which pulls up the feedback voltage to 5.2V. When the feedback voltage is above 4.6V longer than 56ms, OLP is triggered. This protection is also triggered when the SMPS output drops below the nominal value longer than 56ms due to the overload condition. VFB 5.2V VFB-OLP (4.6V) VDD 16V OLP Shutdown Delay Time OLP Triggers Figure 26. OLP Operation VDD Over-Voltage Protection (OVP) VDD over-voltage protection prevents IC damage caused by over voltage on the VDD pin. The OVP is triggered when VDD reaches 25V. A debounce time (typically 30µs) prevents false triggering by switching noise. Over-Temperature Protection (OTP) The OTP circuit is composed of current source and voltage comparators. Typically, an NTC thermistor is connected between the RT and GND pins. Once the voltage of this pin drops below a threshold of 1.02V, PWM output is disabled after tDOTP debounce time. If this pin drops below 0.7V, it triggers the latch-off protection immediately after tDOTP2 debounce time. 8.5V Operating Current 3mA 8uA Normal Operation Fault Situation Normal Operation Figure 25. Auto-Restart Operation Over-Current Protection (OCP) FAN6862R/L has over-current protection thresholds. It is for pulse-by-pulse current limit, which turns off the MOSFET for the remainder of the switching cycle when the sensing voltage of MOSFET drain current reaches the threshold. The other threshold is for the over-current protection, which shuts down the MOSFET gate when the sensing voltage of MOSFET drain current is above the threshold longer than the shutdown delay (56ms). © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 11 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Constant Output Power Limit FAN6862R/L has saw-limiter for pulse-by-pulse current limit, which guarantees almost constant power limit over different line voltages of universal input range. The conventional pulse-by-pulse current limiting scheme has a constant threshold for current limit comparator, which results in a higher power limit for high line voltage. FAN6862R/L has a sawtooth current limit threshold that increases progressively within a switching cycle, which provides lower current limit for high line and makes the actual power limit level almost constant over different line voltages of universal input range, as shown in Figure 27. Leading-Edge Blanking (tLEB) Each time the power MOSFET is switched on, a turn-on spike occurs across the sense-resistor caused by primary-side capacitance and secondary-side rectifier reverse recovery. To avoid premature termination of the switching pulse, a leading-edge blanking time is built in. During this blanking period (360ns), the PWM comparator is disabled and cannot switch off the gate driver. Thus, RC filter with a small RC time constant is enough for current sensing. Figure 28. Current Sense R-C Filter Figure 27. Sawtooth Current Limiter Soft-Start The FAN6862R/L has an internal soft-start circuit that increases pulse-by-pulse current-limit comparator inverting input voltage slowly after it starts. The typical soft-start time is 5ms. The pulsewidth to the power MOSFET is progressively increased to establish the correct working conditions for transformers, rectifier diodes, and capacitors. The voltage on the output capacitors is progressively increased with the intention of smoothly establishing the required output voltage. It also helps prevent transformer saturation and reduces the stress on the secondary diode during startup. © 2009 Fairchild Semiconductor Corporation FAN6862R/L • Rev. 1.0.0 www.fairchildsemi.com 12 FAN6862R/L — Highly Integrated Green-Mode PWM Controller Typical Application Circuit (Netbook Adapter by Flyback) Application Netbook Adapter Fairchild Devices FAN6862R/L Input Voltage Range 90~265VAC Output 19V/2.1A (40W) Features High efficiency (>85.3% at full load) meeting EPS regulation with enough margin Low standby (Pin