IL3843. Fixed Frequency Current Mode PWM Controller TECHNICAL DATA

Transcription

1 TECHNICAL DATA Fixed Frequency Current Mode PWM Controller DESCRIPTION Fixed frequency current-mode PWM controller. It is specially designed for Off Line And DC-to-DC converter applications with minimal external component. This integrated circuit features a trimmed oscillator for precise duty cycle control. a temperature compensated reference, high gain arror amplifier, current sensing comparator, and a high current totempole output ideally suited for driving a power MOSFET. Protection circuitry includes built in under-voltage lockout and current limiting. FEATURES Automatic Feed Forward Compensation High Gain Totem Pole Output Internally Trimmed Bandgap Reference Undervoltage Lockout with Hysteresis Low Start Up Current Optimized for offline converter Double pulse suppression Current mode operation to 500KHz ORDERING INFORMATION N DIP D SOP T A = 0 to 70 C for all packages. ORDERING INFORMATION Device Operating Temperature Range Package N T A =0 to +70 C DIP-8 D T A =0 to +70 C SOP-8

2 PIN FUNCTION DESCRIPTION Pin No. Function Description 1 Compensation This pln is the Error Amplifier output and is made available for loop compensation 2 oltage Feedback This is the inverting input of the Error Amplifier. It is normally connected to the switching power supply outpul through a resistor divider. 3 Current Sense A voltage proportional to inductor current is connected to this input. The PWM uses this. information to terminate the output switch conduction 4 RT/CT The Oscillator frequency and maximum Output duty cycle are programmed by connecting resistor R T to REF and capacitor C T to ground. Operation to 500kHz is possible. 5 GND This pin is the combined conlrol circuitry and power ground 6 Output This output directly drives the gate of a power MOSFET. Peak currents up to 1,0A are sourced and sunk by this pin. 7 cc This pin is the positive supply of the control IC. 8 REF This is the reference output. It provides chsarging current for capacitor C T through resistor R T ABSOLUTE MAXIMUM RATINGS Characteristic Symbol alue Unit Total Power Supply and Zener Current (I CC + I Z ) 30 Output Current I O 1.0 A Output Energy (Capacitive Load per Cycle) W 5.0 J Error Amp Output Sink Current I OE 10 Current Sense and oltage Feedback Inputs in -0.3 to 5.5 Maximum Power T A = 25 o C: DIP-8 SOP-8 P D Thermal Resistance,Junction-to-Air R θja 145 C/W Operating Junction Temperature T J +150 Storage Temperature Range T stg -65 ~ +150 * Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. W o C o C

3 ELECTRICAL CHARACTERISTICS (cc=15 unless otherwise noted) Characteristics Symbol Min Max Unit REFERENCE SECTION Reference Output oltage (I O =1.0, CC =15,T A =25 10 C) (I O =1.0, CC =15,T A = Tlow to Thigh) ref Line Regulation ( CC =12 to 25,T A =Tlow to Thigh) Reg line 20 m Load Regulation (I O =1.0 to 20,T A =Tlow to Thigh) Reg load 25 m Total Output ariation over Line,Load,Temperature (Note1) ( CC =12, I O =1.0,T A =Tlow to Thigh) final ( CC =25, I O =20,T A =Tlow to Thigh) Output Short Circuit Current ( CC =15) I SC OSCILLATOR SECTION Frequency ( CC =15,Tj=25 C,R T =10k,C T =3.3nF) f ( CC =15, T A =Tlow to Thigh,R T =10k,C T =3.3nF) osc khz Frequency Change with oltage Δf osc /Δ 1.0 % ( CC =12 to 25, T A =Tlow to Thigh,R T =10k,C T =3.3nF) Discharge Current (osc=2.0, CC =15) Tj=25 C T A =Tlow to Thigh Idisch ERROR AMPLIFIER SECTION oltage Feedback Input ( O =2.5, CC =15, T A =Tlow to Thigh) FB Input Bias Current ( FB =2.7, CC =15, T A =Tlow to Thigh) I IB -2.0 A Open Loop oltage Gain ( O =2.0 to 4.0, CC =15, T A =Tlow to Thigh) A OL 65 db Unity Gain Bandwidth ( CC =15, T A =Tlow to Thigh) BW 0.7 MHz Power Supply Rejection Ratio ( CC =12 to 25, o=3.0, T A =Tlow to Thigh) PSRR 60 db Output Current Sink ( O =1.1, FB =2.7, CC =15, T A =Tlow to Thigh) Source ( O =5.0, FB =2.3, CC =15, T A =Tlow to Thigh) Output oltage Swing High State ( FB =2.3, CC =15,R L(GND) =15k, T A =Tlow to Thigh) Low State ( FB =2.7, CC =15,R L(5.0) =15k, T A =Tlow to Thigh) I Sink 2.0 I Source -0.5 OH OL CURRENT SENSE SECTION Current Sense Input oltage Gain ( FB =0, CC =15, T A =Tlow to Thigh) Av / Maximum Current Sense Input Threshold ( FB =0, CC =15, T A =Tlow to Thigh) th Input Bias Current ( CC =15, T A =Tlow to Thigh) I IB -10 A Propagation Delay (Current Sense Input to Output) ( CC =15, T A =Tlow to Thigh) t PLH 300 ns

4 ELECTRICAL CHARACTERISTICS (cc=15 unless otherwise noted) OUTPUT SECTION Output oltage Low State (Sink=20, CC =15) (Sink=200, CC =15) High State (Sink=-20, CC =15) (Sink=-200, CC =15) Output oltage with ULO Activated ( CC =6.0, I Sink,=1.0, T A =Tlow to Thigh) Characteristics Symbol Min Max Unit OL OH OL(UL O) Output oltage Rise Time (C L =1.0nF, CC =15, T A =Tlow to Thigh) tr 150 ns Output oltage Fall Time (C L =1.0nF, CC =15, T A =Tlow to Thigh) tf 150 ns ONDEROLTAGE LOCKOUT SECTION Startup Threshold ( CC =0 to 15,T A =Tlow to Thigh) th Minimum Operating oltage After Turn-On ( CC =15 to 0,T A =Tlow to Thigh) CC(min) PWM SECTION Duty Cycle Maximum ( CC =15, T A =Tlow to Thigh,R T =10k,C T =3.3nF) Minimum ( CC =15, T A =Tlow to Thigh,R T =10k,C T =3.3nF) TOTAL DEICE Power Supply Current DCmax DCmin Startup: CC = I CC =15 Operating CC 17 Power Supply Zener oltage (I CC =25, CC =0 to 40) z NOTES: 1 final= ref25 ( Reg line + Reg load )/1000 ref70 ( ref0 )- ref25 ref25 T A =25 C; ref70 T A =70 C; ref0 T A =0 C. 2. Tlow= 0 C ; Thigh=+70 C 94 0 %

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