FAN400A FAIRCHILD | Alldatasheet
Document overview
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Technical content
Features
Linearly Decreasing PWM Frequency Green Mode Under Light-Load and Zero-Load Conditions Constant Voltage (CV) and Constant Current (CC) No Secondary Feedback Low Startup Current: 8μA Low Operating Current: 3.6mA Leading-Edge Blanking Constant Power Limit Universal AC Input Range Synchronized Slope Compensation 140°C OTP Sensor with Hysteresis VDD Over-Voltage Clamping Cycle-by-Cycle Current Limiting Under-Voltage Lockout (UVLO) Fixed PWM Frequency with Hopping Gate Output Maximum Voltage Clamped at 17V Small SSOT-6 Package
Applications
General-purpose, switching mode, power supplies and flyback power converters, such as: Battery Chargers for Cellular Phones, Cordless Phones, PDAs, Digital Cameras, Power Tools Power Adapters for Ink Jet Printers, Video Game Consoles, Portable Audio Players Open-Frame SMPS for TV/DVD Standby and Auxiliary Supplies, Home Appliances, Consumer Electronics Replacement for Linear Transformers and RCC SMPS PC 5V Standby Power
Description
This highly integrated PWM controller provides several features to enhance the performance of low-power flyback converters. To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load and zero-load conditions. This green mode enables the power supply to meet international power conservation requirements. The supply voltage V DD is also used for feedback compensation, to regulate the output voltage without requiring a conventional TL431 and a photo-coupler. Another advantage of the FAN 400A is that the typical startup current is only 8 μA, while the typical operating current can be as low as 3.6mA. A large startup resistance can be used to achieve even higher power conversion efficiency. FAN400A integrates a frequency hopping function internally to reduce EMI emissions with minimum line filters. Built-in synchronized slope compensation maintains the stability of peak current-mode control. Proprietary internal com pensation ensures constant output power limiting over a universal range of AC input voltages, from 90V AC to 264VAC. The FAN400A provides many protection functions. Pulse-by-pulse current limiting ensures constant output current, even if a short circuit occurs. The internal protection circuit disables PWM output if V DD exceeds 22.7V. The gate output is clamped at 17V to protect the power MOS from over-voltage damage. The built-in over-temperature protection (OTP) function shuts down the controller at 140°C with a 30°C hysteresis. The FAN400A is designed to provide a low-cost total solution for flyback converters. It is available in a small- footprint, 6-pin, SSOT-6 package. Related Resources AN-400A Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
Ordering Information
Part Number Operating Temperature Range Package Eco Status Packing Method FAN400ATY -40°C to +105°C SSOT-6 Green Tape & Reel FAN400ANY -40°C to +105°C DIP-8 Green Tube For Fairchild’s definition of “green” please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
Figure 3. Top Mark Figure 4. Pin Configurations
3 NC No connection
threshold. This pin also provides current information for current-mode control.
5 NC No connection
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN400A Rev. 1.0.1 4 FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback Absolute Maximum Ratings Stresses exceeding the absolute maximum ratings may dam age 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 Parameter Min. Max. Unit VVDD DC Supply Voltage (1, 2) 30 V VFB Input Voltage to FB Pin -0.3 7.0 V VSENSE Input Voltage to Sense Pin -0.3 7.0 V TJ Operating Junction Temperature +150 °C SSOT 263.3 °C/W ΘJA Thermal Resistance (Junction-to-Air) DIP 135.7 °C/W TSTG Storage Temperature Range -55 +150 °C TL Lead Temperature (Wave Soldering or IR, 10 Seconds) +260 °C Human Body Model JESD22-A114 4 kV ESD Electrostatic Discharge Capability Machine Model JESD22-A114 200 V Notes: 1. All voltage values, except differential vo ltages, are given with respect to GND pin. 2. Stresses beyond those listed under "absolute maximu m ratings" may cause permanent damage to the device.
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN400A Rev. 1.0.1 5 FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
Electrical Characteristics
Unless otherwise noted, VDD=15V and TA=25°C. Symbol Parameter Conditions Min. Typ. Max. Units VDD Section With Secondary Feedback 20 V VDD-OP Continuously Operation Voltage Without Secondary Feedback 22.7 V VDD-ON Turn-on Threshold Voltage 16 17 18 V VDD-OFF Turn-off Threshold Voltage 7.5 8.0 8.5 V IDD-ST Startup Current V DD=VDD-ON – 0.1V 8 20 μA IDD-OP Operating Supply Current CL=1nF 3.6 4.6 mA VDD-G OFF VDD Low-threshold Voltage to Exit Green-off Mode VDD-OFF+1.2 V Feedback Input Section AV Input-Voltage to Current-Sense Attenuation 2/5 V/V ZFB Input Impedance I FB=0.1mA to 0.2mA 2.4 k Ω VFB-OPEN Open-Loop Voltage 4.5 V FB is Open 20.7 22.7 24.7 V VDD-FB V DD Feedback Threshold Voltage IFB=0.4mA 18.4 20.4 22.4 V Current-Sense Section tPD Propagation Delay 100 150 ns VDD=18V 0.81 V VDD=15V 0.73 V VSTHVA Current Limit Valley Threshold Voltage VDD=10V 0.58 V VDD=18V 1.10 V VDD=15V 1.01 V VSTHFL Current Limit Flat Threshold Voltage VDD=10V 0.81 V tLEB Leading-Edge Blanking Time 250 310 370 ns Figure 5. Saw Limit
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN400A Rev. 1.0.1 6 FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback Electrical Characteristics (Continued) Unless otherwise noted, VDD=15V and TA=25°C. Symbol Parameter Conditions Min. Typ. Max. Units Oscillator Section Center Frequency 60 65 70 fOSC Frequency Hopping Range ±4.1 ±4.6 ±5.1 kHz tHOP Hopping Period 4 ms fOSC-G Green Mode Frequency 14.5 17.0 19.5 KHz VFB-N Green Mode Entry FB Voltage 2.3 2.6 2.9 V VFB-G Green Mode Ending FB Voltage VFB-N - 0.75 V VFB-Z Zero Duty Cycle FB Voltage 1.4 V SG Green Mode Modulation Slope 40 70 100 Hz/mV fDV Frequency Variation vs. V DD Deviation V DD=10 to 22V 2 % fDT Frequency Variation vs. Temperature Deviation T A=-20 to 85°C 1.5 5.0 % Output Section DCYMAX Maximum Duty Cycle 68 73 78 % VGATE-L GATE Low Voltage I O=10mA 1.5 V VGATE-H GATE High Voltage I O=-10mA 8 V tr GATE Rising Time C L=1nF 150 200 250 ns tf GATE Falling Time C L=1nF 70 90 110 ns VGATE- CLAMP GATE Output Clamping Voltage V DD=20V 16 17 18 V Over Temperature Protection (OTP) TOTP Protection Junction Temperature 140 °C TOTP- RESTART Restart Junction Temperature 110 °C
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN400A Rev. 1.0.1 9 FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback Operation Description FAN400A devices integrate m any useful functions for low-power switch-mode power supplies. The following descriptions highlight the key features of the FAN400A. Startup Current The required startup current is only 8 μA. This allows a high-resistance, low-wattage startup resistor to supply the controller’s startup power. A 1.5 M Ω/0.25W startup resistor can be used over a wide input range (100V- 240V AC) with very little power loss. Operating Current The operating current is normally 3.6mA, which results in higher efficiency and reduces the required V DD hold- up capacitance. A 10 μF/25V VDD hold-up capacitor can be used over a wide input range (100V-240V AC) with very little power loss. Green-Mode Operation The proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load and zero-load conditions. The on-time is limited to provide better protection against brownouts and other abnormal conditions. Power supplies using the FAN400A can meet international restrictions regarding standby power-consumption. Constant Voltage (CV) and Constant Current (CC) without Feedback The FAN400A can tightly regulate the output voltage and provide over-current protection without requiring secondary-side feedback signals. For improved CV and CC accuracy, the transformer leakage inductance should be reduced as much as possible. Over-Temperature Protection (OTP) The FAN400A has a built-in temperature sensing circuit to shut down PWM output once the junction temperature exceeds 140 °C. While PWM output is shut down, the V DD voltage gradually drops to the UVLO voltage. Some of the internal circuits are shut down, and V DD gradually starts increasing again. When V DD reaches 17V, all the internal circuits, including the temperature sensing circuit, operate normally. If the junction temperature is still higher than 140 °C, the PWM controller shuts down immediately. This situation continues until the temperature drops below 110 °C. The PWM output is then turned back on. The temperature hysteresis window for the OTP circuit is 30°C. VDD Over-Voltage Clamping VDD over-voltage clamping is built in to prevent damage from over-voltage conditions. When V DD exceeds 22.7V, PWM output is shut down. Over-voltage conditions may be caused by an open photo-coupler loop or a short circuit in the output. Oscillator Operation The oscillation frequency is fixed at 65KHz. Leading-Edge Blanking (LEB) 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 310ns leading- edge blanking time is built in. Conventional RC filtering is not necessary. During this blanking period, the current-limit comparator is disabled and cannot switch off the gate drive. Constant Output Power Limit When the SENSE voltage across the sense resistor R S reaches the threshold voltage (around 1.0V), the output GATE drive is turned off following a small propagation delay, t PD. This propagation delay introduces an additional current proportional to t PD•VIN/LP. The propagation delay is nearly c onstant regardless of the input line voltage VIN. Higher input line voltages result in larger additional currents. Under high input-line voltages the output power limit is higher than under low input-line voltages. Over a wide range of AC input voltages, the variation can be significant. To compensate for this, the threshold voltage is adjusted by adding a positive ramp limit_ramp). This ramp signal can vary from 0.73V to 1.01V and flattens out at 1.01V. A smaller threshold voltage forces the output GATE drive to terminate earlier, reducing total PWM turn-on time and making the output power equal to that of the low line input. This proprietary internal compensation feature ensures a constant output power limit over a wide range of AC input voltages (90V AC to 264VAC). Under Voltage Lockout (UVLO) The turn-on/turn-off thresholds are fixed internally at 17V and 8V. To enable the FAN400A during startup, the hold-up capacitor must first be charged to 17V through the startup resistor. The hol d-up capacitor continues to supply V DD before energy can be delivered from the auxiliary winding of the main transformer. V DD must not drop below 8V during this st artup process. This UVLO hysteresis window ensures t hat the hold-up capacitor can adequately supply VDD during startup. Gate Output The BiCMOS output stage is a fast totem-pole gate driver. Cross-conduction is avoided to minimize heat dissipation, increase efficiency, and enhance reliability. The output driver is clamped by an internal 17V Zener diode to protect the power MO SFET transistors against any harmful over-voltage gate signals.
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN400A Rev. 1.0.1 10 FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback Operation Description (Continued) Slope Compensation The sensed voltage across the current sense resistor is used for current mode control and pulse-by-pulse current limiting. The built-in slope compensation improves power supply stability. Furthermore, it prevents sub-harmonic oscilla tions that normally would occur because of peak current mode control. A positively sloped, synchronized ramp is activated with every switching cycle. The slope of the ramp is: Duty(max.) Duty0.33 × (1) Noise Immunity Noise from the current sense or the control signal may cause significant pulse-width jitter, particularly in continuous-conduction mode. Slope compensation helps alleviate this problem. Good placement and layout practices should be followed. The designer should avoid long PCB traces and component leads. Compensation and filter components should be located near the FAN400A. Finally, increasing the power-MOS gate resistance is advised.
Figure 16. Reference Circuit (without Secondary-Side Feedback)
Figure 17. Reference Circuit (with Secondary-Side Feedback)
5.08 MAX
0.33 MIN
B) ALL DIMENSIONS ARE IN MILLIMETERS. MOLD FLASH, AND TIE BAR EXTRUSIONS. E) DRAWING FILENAME AND REVSION: MKT-N08FREV2. Figure 18. 8-Pin Dip-8 Package the warranty therein, which covers Fairchild products.
Figure 19. 6-Pin SSOT-6 Package the warranty therein, which covers Fairchild products.
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN400A Rev. 1.0.1 15 FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback