 |
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
| Datasheet File OCR Text: |
| Current Mode PWM Controller KA3843A(AM) DESCRIPTION The KA3843AM are fixed frequency current mode PWM controller. They are specially designed for OFF-Line and DC to DC converter applications with a minimal external components. Internally implemented circuits include a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totempole output ideally suited for driving a power MOSFET. Protection circuitry includes built undervoltage lockout and current limiting. The corresponding thresholds for the The KA3843AM are 8.4V(on) and 7.6V (off) The KA3843AM can operate within 100% duty cycle. PIN CONNECTION (TOP VIEW) The KA3843AM has Start-Up Current 0.17mA (typ). FEATURES * * * * Low Start-Up and Operating Current High Current Totem Pole Output Undervoltage Lockout With Hysteresis Operating Frequency Up To 500KHz BLOCK DIAGRAM Absolute Maximum Ratings Characteristic Supply Voltage (low impedance source) Output Current Input Voltage (Analog Inputs pins 2,3) Error Amp Output Sink Current Power Dissipation (TA=250C) Storage Temperature Range Lead Temperature (soldering 5 sec.) Symbol VCC IO VI ISINK (E.A) PO Tstg TL Value 30 1 -0.3 to 5.5 10 1 -65 to150 260 Unit V A V mA W oC oC 1 Current Mode PWM Controller KA3843A(AM) Electrical characteristics (*VCC=15V, RT=10k, CT=3.3nF, TA=00C to +700C, unless otherwise specified) Characteristics Symbol Test Condition Min Typ Max Reference Section Reference Output Voltage Line Regulation Load Regulation Short Circuit Output Current Oscillator Section Oscillation Frequency Frequency Change with Voltage Oscillator Amplitude Error Amplifier Section Input Bias Current Input Voltage Open Loop Voltage Gain Power Supply Rejection Ratio Output Sink Current Output Source Current High Output Voltage Low Output Voltage Current Sense Section Gain Maximum Input Signal Supply Voltage Rejection Input Bias Current Output Section Low Output Voltage High Output Voltage Rise Time Fall Time f f/VCC V(OSC) IBIAS VI(E.A) AVOL PSRR ISINK ISOURCE VOH VOL GV VI(MAX) SVR IBIAS VOL VOH tR tF TJ = 25C 384XA 384XAM 47 47 50 52 0.05 1.6 -0.1 2.42 65 60 2 -0.5 5.0 2.5 90 70 7 -1.0 6.0 0.8 2.85 0.9 3.0 1.0 70 -3.0 0.08 1.4 13.5 13.0 45 35 1.1 3.15 1.1 -10 0.4 2.2 -2 2.58 57 57 1.0 KHz % V A V dB mA mA V VREF VREF VREF ISC TJ = 25C, IREF = 1 mA 12V VCC 25 V 1 mA IREF 20mA TA = 25C 4.9 5.0 6.0 6.0 -100 5.1 20 25 -180 mA Unit V mV 12V VCC 25 V (peak to peak) VFB=3V Vpin1 = 2.5V 2V V0 4V 12V VCC 25 V Vpin2 = 2.7V, Vpin1 = 1.1V Vpin2 = 2.3V, Vpin1 = 5V Vpin2 = 2.3V, RL = 15K to GND Vpin2 = 2.7V, RL = 15K to PIN 8 (Note 1 & 2) V pin1 = 5V (Note1) 12V VCC 25 V (Note 1) Vpin3 = 3V ISINK ISINK ISINK ISINK = = = = 20 mA 200 mA 20 mA 200 mA V/V V dB A 13 12 V TJ = 25C, CL = 1nF (Note 3) TJ = 25C, CL = 1nF (Note 3) 150 150 nS Undervoltage Lockout Section Start Theshold VTH(ST) 3843A(AM) Min. Operating Voltage (After Turn On) PWM Section Max. Duty Cycle Min. Duty Cycle Total Standby Current VOPR(min) 3843A(AM)/45A(AM) D (MAX) D(MAX) 0.17 13 38 3842A(AM)/43A(AM) 7.0 95 7.6 97 8.2 100 7.8 8.4 9.0 V V % 0 0.3 17 384XA(AM) IST Start-Up Current Operating Supply Current ICC (OPR) Vpin3 = Vpin2 = 0V Zener Voltage VZ ICC=25 mA 30 * Adjust VCC above the start threshold before setting it to 15V. Note 1: Parameter measured at trip point of latch with Vpin2=0. Note 2: Gain defined as A=Vpin1/Vpin3 ; 0 Vpin3 0.8V. Note 3: These parameters, although guaranteed, are not 100% tested in production. mA V 2 Current Mode PWM Controller KA3843A(AM) PIN FUNCTION N 1 2 3 4 5 6 7 8 FUNCTION COMP VFB ISENSE RT/CT GROUND OUTPUT VCC Vref DESCRIPTION This pin is the Error Amplifier output and is made for loop compensation. This is the inverting input of the Error Amplifier. It is normally connected to the switching power supply output through a resistor divider. A voltage proportional to inductor current is connected to this input. The PWM uses this information to terminate the output switch conduction. The oscillator frequency and maximum Output duty cycle are programmed by connecting resistor RT to Vref and capacitor CT to ground. This pin is the combined control circuitry and power ground. This output directly drives the gate of a power MOSFET. Peak currents up to 1A are sourced and sink by this pin. This pin is the positive supply of the integrated circuit. This is the reference output. It provides charging current for capacitor CT through resistor RT . APPLICATION INFORMATION Figure 1. Error Amp Configuration WS WS Figure 2. Undervoltage Lockout 3 Current Mode PWM Controller KA3843A(AM) Figure 3. Current Sense Circuit Figure 4. Slope Compensation Techniques 4 Current Mode PWM Controller KA3843A(AM) SCR must be selected for a holding current of less than 0.5mA. The simple two transistor circuit can be used in place of the SCR as shown. Figure 5. Latched Shutdown Figure 6. Error Amplifier Compensation 5 Current Mode PWM Controller KA3843A(AM) Figure 7. External Clock Synchronization Figure 8. Soft-Start Circuit 6 Current Mode PWM Controller KA3843A(AM) TYPICAL PERFORMANCE CHARACTERISTICS Figure 1. Timing Resistor vs. Oscillator Frequency Figure 2. Output Dead-Time vs. Oscillator Frequency Figure 3. Maximum Output Duty Cycle vs. Timing Resistor (3842/43) Figure 4. Error Amp Open-Loop Gain vs. Frequency Figure 5. Current Sense Input Threshold vs. Error Amp Output Voltage Figure 6. Reference Short Circuit Current vs. Temperature 7 Current Mode PWM Controller KA3843A(AM) Figure 7. Output Saturation Voltage vs. Load Current TA = 25C Figure 8. Supply Current vs. Supply Voltage Figure 9. Oscillator and Output Waveforms 8 Current Mode PWM Controller KA3843A(AM) PAD LOCATION Chip size: 2.38 x 1.63 mm Coordinates m X Y 90 110 1050 110 1310 110 2000 150 1700 1280 1680 1450 1310 1410 990 1410 815 1410 460 1390 Pad N 1 2 3 4 5 6 7 8 9 10 Pad Name COMP VFB ISENSE RT/CT POWER GND GND OUT POWER VCC VCC VREF 9 |
Price & Availability of KA3843A
 |
|
|
|
|
All Rights Reserved © IC-ON-LINE 2003 - 2022 |
| [Add Bookmark] [Contact Us] [Link exchange] [Privacy policy] |
|
Mirror Sites : [www.datasheet.hk]
[www.maxim4u.com] [www.ic-on-line.cn]
[www.ic-on-line.com] [www.ic-on-line.net]
[www.alldatasheet.com.cn]
[www.gdcy.com]
[www.gdcy.net] |