FAN7602N

FAN7602 Green Current Mode PWM Controller November 2006 FAN7602 Green Current Mode PWM Controller Features Green Current Mode PWM Control Fixed 65kHz Operation with Frequency Modulation Internal High-Voltage Start-up Switch Burst Mode Operation Line Voltage Feed Forward to Limit Maximum Power Line Under-Voltage Protection Latch Protection & Internal Soft-Start (10ms) Function Overload Protection Over-Voltage Protection Low Operation Current: Typical 1mA 8-pin DIP/SOP Description The FAN7602 is a green current mode PWM controller. It is specially designed for off-line adapter application, DVDP, VCR, LCD monitor application, and auxiliary power supplies. The internal high-voltage start-up switch and the burstmode operation reduce the power loss in standby mode. Because of the internal start-up switch and the burst mode, it is possible to supply 0.5W load, limiting the input power to under 1W when the input line voltage is 265VAC. On no-load condition, the input power is under 0.3W. The maximum power can be limited constantly, regardless of the line voltage change, using the power limit function. The switching frequency is internally fixed at 65kHz and the frequency modulation technique reduces EMI. The FAN7602 includes various protections for the system reliability and the internal soft-start prevents the output voltage overshoot at start-up. Applications Adapter LCD Monitor Power Auxiliary Power Supply Related Application Notes AN6014 - Green Current Mode PWM Controller FAN7602 Ordering Information Part Number FAN7602N FAN7602M FAN7602MX -25°C to +125°C Yes Operating Temp. Range Pb-Free Package 8-DIP 8-SOP Packing Method Rail Rail Tape & Reel Marking Code FAN7602 FAN7602 FAN7602 © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Typical Application Diagram FAN7602 FAN7602 Rev. 02 Figure 1. Typical Flyback Application Internal Block Diagram Vstr 8 6 VCC LUVP 1 2V/1.5V LUVP OLP OVP Latch Auto Restart Protection Latch Protection Reset Circuit VCC OVP SS End 19V 5V Ref UVLO 12V/8V 10ms Soft Start SS End 65kHz Clock with Frequency Modulation PWM Block Driver Circuit Plimit Offset Delay Circuit 5 OUT 3 CS/FB 0.95V/0.88V Latch/ Plimit 2 4V Latch OLP Plimit Offset Soft-Start PWM+ SoftStart Power Limit Plimit Offset Plimit Offset Generator OLP 4 GND FAN7602 Rev. 03 Figure 2. Functional Block Diagram of FAN7602 © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 2 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Pin Assignments Vstr 8 NC 7 VCC 6 OUT 5 FAN7602 YWW 1 LUVP 2 Latch/ Plimit 3 CS/FB 4 GND FAN7602 Rev. 03 Figure 3. Pin Configuration (Top View) Pin Definitions Pin Number 1 2 Pin Name LUVP Latch/Plimit Pin Function 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 Over-Current Protection (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. Start-up Pin. This pin is used to supply IC operating current during IC start-up. After start-up, the internal JFET is turned off to reduce power loss. 3 CS/FB 4 5 GND OUT 6 7 8 VCC NC Vstr © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 3 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Absolute Maximum Ratings The “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. The device should not be operated at these limits. The parametric values defined in the Electrical Characteristics tables are not guaranteed at the absolute maximum ratings. Symbol VCC IOH, IOL VCS/FB VLUVP VLatch Vstr TJ TA Tstg PD VESD_HBM VESD_MM VESD_CDM Supply Voltage Parameter Peak Drive Output Current CS/FB Input Voltage LUVP Input Voltage Latch/Plimit Input Voltage Vstr Input Voltage Operating Junction Temperature Operating Temperature Range Storage Temperature Range Power Dissipation ESD Capability, Human Body Model ESD Capability, Machine Model ESD Capability, Charged Device Model Value 20 +450/-600 -0.3 to 20 -0.3 to 10 -0.3 to 10 600 150 -25 to 125 -55 to 150 1.2 2.0 300 500 Unit V mA V V V V °C °C °C W kV V V Thermal Impedance Symbol θJA(1) Note: 1. Regarding the test environment and PCB type, please refer to JESD51-2 and JESD51-10. Parameter Thermal Resistance, Junction-to-Ambient 8-DIP Value 100 Unit °C/W © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 4 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Electrical Characteristics VCC = 14V, TA = -25°C~125°C, unless otherwise specified. Symbol START UP SECTION Istr Vth(start) Vth(stop) HY(uvlo) Ist ICC TSS FOSC ΔF VCS/FB1 tD DMAX DMIN VCS/FB2 VCS/FB3 KPlimit VOH VOL tr tf Note: Parameter Vstr Start-up Current Start Threshold Voltage Stop Threshold Voltage UVLO Hysteresis Start-up Supply Current Operating Supply Current Soft-Start Time(2) Operating Frequency Frequency Modulation CS/FB Threshold Voltage Propagation Delay to Output(2) Maximum Duty Cycle Minimum Duty Cycle Burst On Threshold Voltage Burst Off Threshold Voltage Offset Gain Output Voltage High Output Voltage Low Rising Time(2) Falling Time(2) Condition Vstr = 30V, TA = 25°C VCC increasing VCC decreasing Min. 0.7 11 7 3.6 Typ. 1 12 8 4 250 1 Max. 1.4 13 9 4.4 320 1.5 15 73 1.1 150 80 0 Unit mA V V V μA mA ms kHz kHz V ns % % V V UNDER VOLTAGE LOCK OUT SECTION SUPPLY CURRENT SECTION TA = 25°C Output no switching 5 VCS/FB = 0.2V, TA = 25°C TA = 25°C 59 0.9 70 SOFT-START SECTION 10 65 ±2 1.0 100 75 PWM SECTION BURST MODE SECTION TA = 25°C TA = 25°C VLatch/Plimit = 2V, TA = 25°C TA = 25°C, Isource = 100mA TA = 25°C, Isink = 100mA TA = 25°C, Cl = 1nF TA = 25°C, Cl = 1nF 0.84 0.77 0.12 11.5 0.95 0.88 0.16 12 1 45 35 1.06 0.99 0.20 14 2.5 150 150 V V ns ns POWER LIMIT SECTION OUTPUT SECTION 2. These parameters, although guaranteed by design, are not tested in production. © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 5 www.fairchildsemi.com FAN7602 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 Note: Latch Voltage Parameter Condition Min. 3.6 Typ. 4 22 37 0 2 1.5 19 Max. 4.4 24 44 0.1 2.1 1.6 20 Unit V ms ms V V V V Overload Protection Time (3) 20 30 TA = 25°C TA = 25°C TA = 25°C 1.9 1.4 18 Overload Protection Time at Start-up Overload Protection Level Line Under-Voltage Protection On to Off Line Under-Voltage Protection Off to On Over Voltage Protection 3. These parameters, although guaranteed by design, are not tested in production. © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 6 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Typical Performance Characteristics 12.8 12.4 8.8 8.4 VTH[V] VTL[V] 12.0 11.6 11.2 -25 0 25 50 75 100 125 8.0 7.6 7.2 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 4. Start Threshold Voltage vs. Temp. Figure 5. Stop Threshold Voltage vs. Temp. 4.4 4.3 350 UVLO Hysteresis [V] 4.2 300 4.0 3.9 3.8 3.7 3.6 -25 0 25 50 75 100 125 Ist [μA] 4.1 250 200 150 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 6. UVLO Hysteresis vs. Temp. Figure 7. Start-up Supply Current vs. Temp. 1.5 1.4 1.3 1.3 1.2 Iop [mA] Istr [mA] 0 25 50 75 100 125 1.2 1.1 1.0 0.9 0.8 -25 1.1 1.0 0.9 0.8 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 8. Operating Supply Current vs. Temp. Figure 9. Vstr Star-up Current vs. Temp. © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 7 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Typical Performance Characteristics (Continued) 1.10 1.05 CSFB2 CSFB3 70 68 CS/FB Threshold [V] 1.00 0.95 0.90 0.85 0.80 0.75 0.70 -25 0 25 50 75 100 125 FOSC [kHz] 66 64 62 60 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 10. Burst On/Off Voltage vs. Temp. Figure 11. Operating Frequency vs. Temp. 0.20 0.18 0.16 0.14 0.12 0.10 -25 80 78 DMAX [%] 0 25 50 75 100 125 Kplimit 76 74 72 70 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 12. Offset Gain vs. Temp. Figure 13. Maximum Duty Cycle vs. Temp. 20.0 19.6 19.2 18.8 18.4 18.0 -25 4.4 4.2 VLATCH [V] 0 25 50 75 100 125 VOVP [V] 4.0 3.8 3.6 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 14. OVP Voltage vs. Temp. Figure 15. Latch Voltage vs. Temp. © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 8 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Typical Performance Characteristics (Continued) 2.10 1.70 1.65 2.05 VLUVPoff [V] VLUVPon [V] 0 25 50 75 100 125 1.60 1.55 1.50 2.00 1.95 1.45 1.90 -25 1.40 -25 0 25 50 75 100 125 Temperature [°C] Temperature [°C] Figure 16. LUVP On to Off Voltage vs. Temp. Figure 17. LUVP Off to On Voltage vs. Temp. CSFB1 Threshold voltage [V] 1.08 1.04 1.00 0.96 0.92 -25 0 25 50 75 100 125 Temperature [°C] Figure 18. CS/FB Threshold Voltage vs. Temp. © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 9 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Applications Information 1. Start-up Circuit and Soft-Start Block The FAN7602 contains a start-up switch to reduce the power loss of the external start-up circuit of the conventional PWM converters. The internal start-up circuit charges the VCC capacitor with 0.9mA current source if the AC line is connected. The start-up switch is turned off 15ms after IC starts up, as shown in Figure 19. The softstart 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 start-up 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 softstart voltage. The soft-start voltage starts from 0.5V and the soft-start ends when it reaches 1V and the soft-start time is 10ms. The start-up switch is turned off when the soft-start voltage reaches 1.5V. 12V 8V Start-up Current 1.5V 1V 0.5V Soft-Start Voltage Soft-Start Time (10ms) t 5ms FAN7602 Rev. 02 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. 67kHz 16 steps 1 step=250Hz 63kHz 125Hz FAN7602 Rev. 02 Figure 20. Frequency Modulation 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. The CS/FB pin voltage is compared with PWM+ that is 1V - Plimit offset as shown in Figure 22. If the CS/FB voltage meets PWM+, the output drive is shut off. As shown in Figure 22, 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. In general, the maximum output power increases as the input voltage increases because the current slope during switch on-time increases. To limit the output power of the converter constantly, the power limit function is included in the FAN7602. 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, controlling 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. VCC Figure 19. Start-up Current and VCC Voltage 2. Oscillator Block The oscillator frequency is set internally and a frequency modulation (FM) function reduces EMI. The average frequency is 65kHz and the modulation frequency is ±2kHz. The frequency varies from 63kHz to 67kHz with 16 steps. The frequency step is 250Hz and FM frequency is 125Hz, as shown in Figure 20. VCC Plimit Offset Power Limit 3 RFB CS/FB CF RS FAN7602 Rev. 02 IFB RF Isw PWM Comparator PWM+ Soft-Start 3. Current Sense and Feedback Block The FAN7602 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. © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 10 Figure 21. Current Sense and Feedback Circuits www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller 1V PWM+ CS/FB Power Limit Offset counting. If the OLP condition persists for 22ms, the timer generates the OLP signal. And this protection is reset by the UVLO. The OLP block is enabled after the soft-start finishes. Clock OLP 22ms Timer Soft-Start 50mV FAN7602 Rev. 02 FB Offset 3 CS/FB GND On Time (a) Low Power Limit Offset Case 1V PWM+ CS/FB Figure 24. Overload Protection Circuit Power Limit Offset FB Offset GND On Time (b) High Power Limit Offset Case FAN7602 Rev. 02 Figure 22. CS/FB Pin Voltage Waveforms 4. Burst Mode Block The FAN7602 contains the burst mode block to reduce the power loss at a light load and no load as the FAN7601. 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 FAN7602 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. O ffs e t D e la y C irc u it 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. In the FAN7602, 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. Vin 1 − + 2V/1.5V LUVP FAN7602 Rev. 02 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. + − B u rs t+ 3 C S /F B 0 .9 5 V /0 .8 8 V FA N7602 R ev. 02 Figure 23. Burst Mode Block 5. Protection Block The FAN7602 contains several protection functions to improve system reliability. 5.1 Overload Protection The FAN7602 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 6. Output Drive Block The FAN7602 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, 35ns respectively with a 1nF load. © 2006 Fairchild Semiconductor Corporation FAN7602 Rev. 1.0.2 11 www.fairchildsemi.com FAN7602 Green Current Mode PWM Controller Typical application circuit Application Adapter Output power 48W Input voltage Universal input (85~265VAC) Output voltage 12V Features Low stand-by power (