FAN7602CN

FAN7602C — Green Current Mode PWM Controller April 2009 FAN7602C Green Current Mode PWM Controller Features Green Current Mode PWM Controller Random Frequency Fluctuation for Low EMI Internal High-Voltage Startup Switch Burst Mode Operation Line Voltage Feedforward to Limit Maximum Power Line Under-Voltage Protection Latch Protection & Internal Soft-Start (10ms) Function Overload Protection Over-Voltage Protection Over-Temperature Protection Low Operation Current: 1mA Typical 8-Pin DIP/SOP Description The FAN7602C is a green current-mode PWM controller. It is specially designed for off-line adapter applications; DVDP, VCR, LCD monitor applications; and auxiliary power supplies. The internal high-voltage startup switch and the burst mode operation reduce the power loss in standby mode. As a result, the input power is lower than 1W when the input line voltage is 265VAC and the load is 0.5W. At noload condition, input power is under 0.15W. The maximum power can be limited constantly, regardless of the line voltage change, using the power limit function. The switching frequency is not fixed and it has random frequency fluctuation. The FAN7602C includes various protections for the system reliability and the internal soft-start prevents the output voltage over-shoot at startup. Applications Adapter LCD Monitor Power Auxiliary Power Supply Related Resources AN-6014- Green Current Mode PWM Controller (Except for frequency fluctuation part in AN-6014) Ordering Information Part Number FAN7602CN FAN7602CM FAN7602CMX -40°C to +150°C RoHS Operating Junction Temperature Eco Status Package 8-DIP 8-SOP Packing Method Rail Rail Tape and Reel Top Mark FAN7602C FAN7602C FAN7602C For Fairchild’s definition of Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html. © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com FAN7602C — Green Current Mode PWM Controller Typical Application Diagram LUVP Latch/ Plimit CS/FB GND VSTR NC FAN7602C VCC Out Figure 1. Typical Flyback Application Internal Block Diagram VSTR 8 6 VCC LUVP 1 2V/1.5V LUVP OLP TSD OVP Latch Auto Restart Protection SS End OVP 19V 5V Ref Latch Protection Reset Circuit Vcc UVLO 12V/8V 10ms Soft Start SS End PWM Block Delay Circuit Driver Circuit Plimit Offset 5 OUT OSC Random Latch/ 2 Plimit 4V Plimit Offset Generator Plimit Offset Soft Start Latch OLP 3 CS/FB 0.95V/0.88V PWM+ Soft Start Power Limit Plimit Offset OLP 4 GND Figure 2. Functional Block Diagram © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 2 FAN7602C — Green Current Mode PWM Controller Pin Configuration Figure 3. Pin Configuration (Top View) Pin Definitions Pin # 1 2 Name LUVP Latch/Plimit Description Line Under-Voltage Protection Pin. This pin is used to protect the set when the input voltage is lower than the rated input voltage range. Latch Protection and Power Limit Pin. When the pin voltage exceeds 4V, the latch protection works. The latch protection is reset when the VCC voltage is lower than 5V. For the power limit function, the OCP level decreases as the pin voltage increases. Current Sense and Feedback Pin. This pin is used to sense the MOSFET current for the current mode PWM and OCP. The output voltage feedback information and the current sense information are added using an external RC filter. Ground Pin. This pin is used for the ground potential of all the pins. For proper operation, the signal ground and the power ground should be separated. Gate Drive Output Pin. This pin is an output pin to drive an external MOSFET. The peak sourcing current is 450mA and the peak sinking current is 600mA. For proper operation, the stray inductance in the gate driving path must be minimized. Supply Voltage Pin. IC operating current and MOSFET driving current are supplied using this pin. No Connection. Startup Pin. This pin is used to supply IC operating current during IC startup. After startup, the internal JFET is turned off to reduce power loss. 3 4 5 6 7 8 CS/FB GND OUT VCC NC VSTR © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 3 FAN7602C — Green Current 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. Symbol VCC IO VCS/FB VLUVP VLatch VSTR TJ TSTG PD ESD Supply Voltage Output Current CS/FB Input Voltage LUVP Input Voltage Latch/Plimit Input Voltage VSTR Input Voltage Junction Temperature Parameter Min. -600 -0.3 -0.3 -0.3 Max. 25 +450 20 10 10 600 +150 Unit V mA V V V V °C °C W kV Recommended Operating Junction Temperature Storage Temperature Range Power Dissipation Electrostatic Discharge Capability Human Body Model, JESD22-A114 Charged Device Model, JESD22-C101 -40 -55 +150 +150 1.2 3.5 2.0 Thermal Impedance Symbol θJA (1) Parameter Thermal Resistance , Junction-to-Ambient 8-DIP Value 100 Unit °C/W Note: 1. Regarding the test environment and PCB type, please refer to JESD51-2 and JESD51-10. © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 4 FAN7602C — Green Current Mode PWM Controller Electrical Characteristics VCC = 14V, TA = -25°C~125°C, unless otherwise specified. Symbol Startup Section ISTR Parameter Condition Min. Typ. Max. Unit VSTR Startup Current VSTR = 30V, TA = 25°C 0.7 1.0 1.4 mA Under Voltage Lock Out Section Vth(start) Vth(stop) HY(uvlo) Start Threshold Voltage Stop Threshold Voltage UVLO Hysteresis VCC Increasing VCC Decreasing 11 7 3.6 12 8 4.0 13 9 4.4 V V V Supply Current Section IST ICC Startup Supply Current Operating Supply Current TA = 25°C Output Not Switching 250 1.0 320 1.5 µA mA Soft-Start Section tSS Soft-Start Time (2) 5 10 15 ms PWM Section fOSC ᅀfOSC VCS/FB1 tD DMAX DMIN Operating Frequency Frequency Fluctuation (2) VCS/FB = 0.2V, TA = 25°C 59 65 ±3 73 kHz kHz CS/FB Threshold Voltage Propagation Delay to Output Maximum Duty Cycle Minimum Duty Cycle (2) TA = 25°C 0.9 1.0 100 1.1 150 80 0 V ns % % 70 75 Burst Mode Section VCS/FB2 VCS/FB3 Burst On Threshold Voltage Burst Off Threshold Voltage TA = 25°C TA = 25°C 0.84 0.77 0.95 0.88 1.06 0.99 V V Power Limit Section KPlimit Offset Gain VLatch/Plimit = 2V, TA = 25°C 0.12 0.16 0.20 Output Section VOH VOL tR tF Output Voltage High Output Voltage Low Rising Time (2) (2) TA = 25°C, Isource = 100mA TA = 25°C, Isink = 100mA TA = 25°C, CL = 1nF TA = 25°C, CL= 1nF 11.5 12.0 1.0 45 35 14.0 2.5 150 150 V V ns ns Falling Time Continued on the following page… © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 5 FAN7602C — Green Current Mode PWM Controller Electrical Characteristics (Continued) VCC = 14V, TA = -25°C~125°C, unless otherwise specified. Symbol Protection Section VLATCH tOLP tOLP_ST VOLP VLUVPoff VLUVPon VOVP TSD HYS Parameter Condition Min. Typ. Max. Unit Latch Voltage Overload Protection Time (2) 3.6 20 30 4.0 22 37 0 4.4 24 44 0.1 2.1 1.6 20 V ms ms V V V V °C °C Overload Protection Time at Startup Overload Protection Level Line Under-Voltage Protection On to Off Line Under-Voltage Protection Off to On Over-Voltage Protection Shutdown Temperature (2) TA = 25°C TA = 25°C TA = 25°C 1.9 1.4 18 2.0 1.5 19 170 60 Note: 2. These parameters, although guaranteed, are not 100% tested in production. © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 6 FAN7602C — Green Current Mode PWM Controller Typical Performance Characteristics 1. 20 1. 15 1. 10 1. 05 1. 00 0. 95 0. 90 0. 85 0. 80 -50 -25 0 25 50 75 100 125 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0 .80 -50 -25 0 25 50 75 100 125 Temperature [°C] Figure 4. Start Threshold Voltage vs. Temperature Figure 5. Stop Threshold Voltage vs. Temperature 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0 .80 -50 -25 0 25 50 75 100 125 1.40 1.30 1.20 1.10 1.00 0.90 0.80 0.70 0.60 -50 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 6. UVLO Hysteresis vs. Temperature Figure 7. Startup Threshold Current vs. Temperature 1.50 1.40 1.30 1.20 1.15 1.10 1.05 1.00 Normalized 1.20 1.10 1.00 0.90 0.80 -50 -25 0 25 50 75 100 125 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 8. Operating Supply Current vs. Temperature Figure 9. VSTR Startup Current vs. Temperature © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 7 FAN7602C — Green Current Mode PWM Controller Typical Performance Characteristics (Continued). 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 CSFB2 CSFB3 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 10. Burst On/Off Voltage vs. Temperature Figure 11. Operating Frequency vs. Temperature 1.20 1.15 1.10 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Normalized 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Temperature [°C] Figure 12. Offset Gain vs. Temperature Figure 13. Maximum Duty Cycle vs. Temperature 1.20 1.15 1.10 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Normalized 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Temperature [°C] Figure 14. OVP Voltage vs. Temperature Figure 15. Latch Voltage vs. Temperature © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 8 FAN7602C — Green Current Mode PWM Controller Typical Performance Characteristics (Continued) 1.20 1.15 1.10 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Normalized 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Temperature [°C] Figure 16. LUVP On-to-Off Voltage vs. Temperature Figure 17. LUVP Off-to-On Voltage vs. Temperature 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 -50 -25 0 25 50 75 100 125 Temperature [°C] Figure 18. CS/FB Threshold Voltage vs. Temperature © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 9 FAN7602C — Green Current Mode PWM Controller Application Information 1. Startup Circuit and Soft-Start Block The FAN7602C contains a startup switch to reduce the power loss of the external startup circuit of the conventional PWM converters. The internal startup circuit charges the VCC capacitor with 0.9mA current source if the AC line is connected. The startup switch is turned off 15ms after IC starts up, as shown in Figure 19. The soft-start function starts when the VCC voltage reaches the start threshold voltage of 12V and ends when the internal soft-start voltage reaches 1V. The internal startup circuit starts charging the VCC capacitor again if the VCC voltage is lowered to the minimum operating voltage, 8V. The UVLO block shuts down the output drive circuit and some blocks to reduce the IC operating current and the internal soft-start voltage drops to zero. If the VCC voltage reaches the start threshold voltage, the IC starts switching again and the soft-start block works as well. During the soft-start, pulse-width modulated (PWM) comparator compares the CS/FB pin voltage with the soft-start voltage. The soft-start voltage starts from 0.5V and the soft-start ends when it reaches 1V and the softstart time is 10ms. The startup switch is turned off when the soft-start voltage reaches 1.3V. Figure 20. Frequency Fluctuation Waveform 3. Current Sense and Feedback Block The FAN7602C performs the current sensing for the current mode PWM and the output voltage feedback with only one pin, pin 3. To achieve the two functions with one pin, an internal LEB (leading-edge blanking) circuit to filter the current sense noise is not included because the external RC filter is necessary to add the output voltage feedback information and the current sense information. Figure 21 shows the current sense and feedback circuits. RS is the current sense resistor to sense the switch current. The current sense information is filtered by an RC filter composed of RF and CF. According to the output voltage feedback information, IFB charges or stops charging CF to adjust the offset voltage. If IFB is zero, CF is discharged through RF and RS to lower the offset voltage. VCC Plimit Offset Power Limit 3 RFB CS/FB CF RS IFB RF Isw Figure 19. Startup Current and VCC Voltage PWM Comparator PWM+ Soft-Start 2. Oscillator Block The oscillator frequency is set internally and FAN7602C has a random frequency fluctuation function. Fluctuation of the switching frequency of a switched power supply can reduce EMI by spreading the energy over a wider frequency range than the bandwidth measured by the EMI test equipment. The amount of EMI reduction is directly related to the range of the frequency variation. The range of frequency variation is fixed internally; however, its selection is randomly chosen by the combination of external feedback voltage and internal free-running oscillator. This randomly chosen switching frequency effectively spreads the EMI noise nearby switching frequency and allows the use of a cost-effective inductor instead of an AC input line filter to satisfy the world-wide EMI requirements. Figure 21. Current Sense and Feedback Circuits Figure 22 shows typical voltage waveforms of the CS/FB pin. The current sense waveform is added to the offset voltage, as shown in the Figure 22. The CS/FB pin voltage is compared with PWM that is 1V - Plimit offset. If the CS/FB voltage meets PWM+, the output drive is shut off. If the feedback offset voltage is LOW, the switch on-time is increased. If the feedback offset voltage is HIGH, the switch on-time is decreased. In this way, the duty cycle is controlled according to the output load condition. Generally, the maximum output power increases as input voltage increases because the current slope during switch on-time increases. © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 www.fairchildsemi.com 10 FAN7602C — Green Current Mode PWM Controller To limit the output power of the converter constantly, the power limit function is included in FAN7602C. Sensing the converter input voltage through the Latch/Plimit pin, the Plimit offset voltage is subtracted from 1V. As shown in Figure 22, the Plimit offset voltage is subtracted from 1V and the switch on-time decreases as the Plimit offset voltage increases. If the converter input voltage increases, the switch on-time decreases, keeping the output power constant. The offset voltage is proportional to the Latch/Plimit pin voltage and the gain is 0.16. If the Latch/Plimit voltage is 1V, the offset voltage is 0.16V. 1V PWM+ CS/FB Power Limit Offset 5.1 Overload Protection (OLP) The FAN7602C contains the overload protection function. If the output load is higher than the rated output current, the output voltage drops and the feedback error amplifier is saturated. The offset of the CS/FB voltage representing the feedback information is almost zero. As shown in Figure 24, the CS/FB voltage is compared with 50mV reference when the internal clock signal is HIGH and, if the voltage is lower than 50mV, the OLP timer starts counting. If the OLP condition persists for 22ms, the timer generates the OLP signal. The protection is reset by the UVLO. The OLP block is enabled after the soft-start finishes. FB Offset GND On Time (a) Low Power Limit Offset Case Figure 24. Overload Protection Circuit 5.2 Line Under-Voltage Protection If the input voltage of the converter is lower than the minimum operating voltage, the converter input current increases too much, causing components failure. Therefore, if the input voltage is LOW, the converter should be protected. The LUVP circuit senses the input voltage using the LUVP pin and, if this voltage is lower than 2V, the LUVP signal is generated. The comparator has 0.5V hysteresis. If the LUVP signal is generated, the output drive block is shut down, the output voltage feedback loop is saturated, and the OLP works if the LUVP condition persists more than 22ms. 1V PWM+ CS/FB Power Limit Offset FB Offset GND On Time (b) High Power Limit Offset Case Figure 22. CS/FB Pin Voltage Waveforms 4. Burst Mode Block The FAN7602C contains the burst-mode block to reduce the power loss at a light load and no load. A hysteresis comparator senses the offset voltage of the Burst+ for the burst mode, as shown in Figure 23. The Burst+ is the sum of the CS/FB voltage and Plimit offset voltage. The FAN7602C enters the burst mode when the offset voltage of the Burst+ is higher than 0.95V and exits the burst mode when the offset voltage is lower than 0.88V. The offset voltage is sensed during the switch off time. − + Figure 25. Line UVP Circuit 5.3 Latch Protection The latch protection is provided to protect the system against abnormal conditions using the Latch/Plimit pin. The Latch/Plimit pin can be used for the output overvoltage protection and/or other protections. If the Latch/ Plimit pin voltage is made higher than 4V by an external circuit, the IC is shut down. The latch protection is reset when the VCC voltage is lower than 5V. 5.4 Over-Voltage Protection (OVP) If the VCC voltage reaches 19V, the IC shuts down and the OVP protection is reset when the VCC voltage is lower than 5V. + − Figure 23. Burst Mode Block 6. Output Drive Block The FAN7602C contains a single totem-pole output stage to drive a power MOSFET. The drive output is capable of up to 450mA sourcing current and 600mA sinking current with typical rise and fall time of 45ns and 35ns, respectively, with a 1nF load. www.fairchildsemi.com 11 5. Protection Block The FAN7602C contains several protection functions to improve system reliability. © 2009 Fairchild Semiconductor Corporation FAN7602C • Rev. 1.0.0 FAN7602C — Green Current Mode PWM Controller Typical Application Circuit Application Adaptor Output Power 48W Input Voltage Universal input (85 ~ 265 VAC) Output Voltage 12V Features Low stand-by power (