AS2208 Primary Side PWM Controller Preliminary Specification Features Description • • Low Startup Current • Oscillator trimmed for precision duty cycle clamp The AS2208 is a simplified pulse width modulation controller, offering similar functionality as that of the AS3842. Based on the AS2214, the AS2208 provides the additional features of low startup current and overvoltage latching, making it a good solution for adapter applications. • Standard temperature range extended to 105°C • • • Remote on / off control Single-start or auto-restart modes The PWM function is controlled by the current sense comparator for normal current mode control. The COMP pin, which serves as an input to the current sense comparator, provides a 1 mA current source which can be tied directly to the control loop optocoupler. The output stage is a high current totem pole output that sees only 85 ns delay from the PWM comparator. Self limiting supply Voltage Standard current mode control The AS2208 requires only 100 µA of startup current. The undervoltage lockout (UVLO) thresholds are nominally 14V for turn on and 8 V for turn off. The VREG pin, based on a trimmed bandgap reference, provides a temperature compensated 5 V to loads of up to 50 mA. The oscillator discharge current is trimmed to provide guaranteed duty cycle clamping. Pin Configuration — Top view 8L SOIC (D) PDIP (N) COMP 1 8 VREG ISNS 2 7 RT/CT 3 OV 4 COMP 1 8 VREG VCC ISNS 2 7 VCC 6 OUT RT/CT 3 6 OUT 5 GND OV 4 5 GND Ordering Information Package Temperature Range Order Code 8-Pin Plastic DIP 0 to 105° C AS2208N 8-Pin Plastic SOIC 0 to 105° C AS2208D ASTEC Semiconductor 77 Primary Side PWM Controller AS2208 Functional Block Diagram VCC 5V enable VREG ENBL S 5V Reg. V REG UVLO Q R ENBL Latch Enable S Q VREG 2V5 R Fault Latch ENBL OV 3V9 S Q R VOV Latch 1V7 ISNS VCC 1mA COMP (FAULT) 2R CM PWM VCC (PWM) 1V RT/CT OUT R (BLANK) OSC ASTEC Semiconductor 78 GND Primary Side PWM Controller AS2208 Pin Function Description Pin Number Function Description 1 COMP This is the inverting input to the PWM comparator. A divided and level shifted representation of this voltage is compared to the ISNS input to determine OUT duty cycle. A 1 mA current source is provided as a pull-up for an optocoupler. 2 ISNS A voltage proportional to inductor current is connected to this pin. The PWM uses this information to terminate the gate drive of the output. 3 RT/CT Oscillator frequency and maximum duty cycle are set by connecting a resistor (RT) to VREG and a capacitor (CT) to ground. 4 OV This pin latches OUT low when pulled above 2.5 V. The latch can be reset by pulling OV above 4 V then back to ground. 5 GND Circuit common ground. 6 OUT This totem pole output is designed to directly drive a power MOSFET switch capable of sourcing and sinking peak currents up to 1 A. 7 VCC Positive supply voltage for the IC. 8 VREG Output of 5V series regulator. Absolute Maximum Ratings Parameter Symbol Rating Unit VCC VCC IREF IOUT VOUT PD TJ TSTG TL Self-Limiting 20 200 1 20 500 150 – 65 to 150 300 V V mA A V mW °C °C °C Supply Voltage (ICC < 30 mA) Supply Voltage (Low Impedance Source) Reference Current Output Current Output Voltage Continuous Power Dissipation at 25° C Junction Temperature Storage Temperature Range Lead Temperature, Soldering 10 Seconds Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. Recommended Conditions Typical Thermal Resistance Parameter Symbol Rating Unit Package θJA θJC Typical Derating Supply Voltage VCC 10 - 15 V 8L PDIP 95° C/W 50° C/W 10.5 mW/°C Oscillator FOSC 50 - 250 kHz 8L SOIC 175° C/W 45° C/W 5.7 mW/°C ASTEC Semiconductor 79 Primary Side PWM Controller AS2208 Electrical Characteristics Electrical Characteristics are guaranteed over full junction temperature range (0 to 105° C). Ambient temperature must be derated based on power dissipation and package thermal characteristics. Unless otherwise specified, the conditions of test are VCC = 15 V; BOK = 3 V; OV = 0V; RT = 680 Ω; CT = 10 nF. To override UVLO, VCC should be raised above 18 V prior to test. Parameter Symbol Test Condition Min Typ Max Unit 4.90 5.00 5.10 V 5 V Regulator Output Voltage VREG IREG = 1 mA, TJ= 25° C Line Regulation PSRR 9 ≤ VCC ≤ 18 V 5 15 mV 1≤ IREG ≤ 20mA 5 15 mV 0.2 0.4 mV/°C 5.15 V 25 mV Load Regulation Temperature Stability TCREG Total Output Variation Line, Load,Temperature Long-Term Stability Over 1,000 hrs at 25°C 5 10 ≤ f ≤ 100kHz, TJ = 25°C 50 Output Noise Voltage Maximum Source Current VNOISE 4.85 µV IMAX VREG = 4.8 V 30 120 180 mA FOSC TJ =25°C 108 Oscillator Initial Accuracy Voltage Stability 120 132 kHz 9 ≤ VCC ≤ 18 V 0.2 1 % 5 % 1.55 V Temperature Stability TCF TMIN ≤ TJ ≤ TMAX Amplitude VOSC VRT/CT peak-to-peak Upper Trip Point VH 2.80 V Lower Trip Point VL 1.25 V Discharge Current IDSC RT =680 Ω, CT =10nF, TJ =25°C Duty cycle Limit Over-Temperature Shutdown 7.50 8.70 9.50 mA 46 50 55 % TOT °C 140 Current Sense Comparator Transfer Gain ISNS Level Shift AV ISNS VLS -0.2 ≤ VISNS ≤ 0.8 V VISNS = 0 V Maximum Input Signal VISNS MAX VCOMP =+5 V Input Bias Current IBIAS VCOMP =+5 V ISNS COMP Source Current ICOMPH COMP Swing High VCOMPH Power Supply Rejection Ratio PSRR Propagation Delay to Output tPB 2.85 3.00 3.15 1.50 1.00 VCOMP =+5 V 9 ≤ VCC ≤ 18 V 80 V 1.08 1.20 V -1 -10 µA 0.6 1.0 mA 5.2 5.6 V 70 dB 85 ASTEC Semiconductor V/V 150 ns Primary Side PWM Controller Electrical Characteristics AS2208 (cont’d) Electrical Characteristics are guaranteed over full junction temperature range (0 to 105° C). Ambient temperature must be derated based on power dissipation and package thermal characteristics. Unless otherwise specified, the conditions of test are VCC = 15 V; BOK = 3 V; OV = 0V; RT = 680 Ω; CT = 10 nF. To override UVLO, VCC should be raised above 18 V prior to test. Parameter Symbol Test Condition Min Typ Max Unit Output Output Low Level VOL ISINK = 20 mA 0.1 0.4 V Output Low Level VOL ISINK = 150 mA 1.5 2.2 V Output High Level VOH ISOURCE = 20 mA 13 13.5 V Output High Level VOH ISOURCE = 150 mA 12 13 V Rise Time tR CL = 1 nF 50 150 ns Fall Time tF CL = 1 nF 50 150 ns 97 100 % Maximum Duty Cycle DMAX 94 Minimum Duty Cycle DMIN 0 VOV 2.50 2.80 3.10 V OV Reset Threshold VVOVH 3.80 4.00 4.50 V OV Clear Threshold VVOVL 1.10 1.75 2.20 V OV Bias Current IBIAS OV -1 -0.2 1 µA % Over-Voltage Input OV Threshold VREG = 5 V, VOV ≤ OV Threshold Under Voltage Lockout Startup Threshold VCC (ON) 12.5 14.0 15.8 V Minimum Operating Voltage after Turn-on VCC (OFF) 7.3 8.0 8.5 AV 105 150 µA 12 20 mA Startup Current Operating Supply Current Supply Voltage Clamp Output Impedance to GND in UVLO State ICC VCC = 13 V ICC VCC Zener ZOUT ICC = 30 mA VCC = 6 V 18 V 22.0 kΩ ASTEC reserves the right to make changes without further notice to any products described herein to improve reliability, function, or design. ASTEC does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights or the rights of others. ASTEC products are not authorized for use as components in life support devices or systems intended for surgical implant into the body or intended to support or sustain life. Buyer agrees to notify ASTEC of any such intended end use whereupon ASTEC will determine availability and suitability of its products for the intended use. ASTEC and the ASTEC logo are trademarks of ASTEC (BSR) PLC. ASTEC SEMICONDUCTOR 255 Sinclair Frontage Road • Milpitas, California 95035 • Tel. (408) 263-8300 • FAX (408) 263-8340 ASTEC Semiconductor 81 Primary Side PWM Controller AS2208 Notes ASTEC Semiconductor 82