KA3524

www.fairchildsemi.com KA3524 SMPS Controller Features Description • • • • • • The KA3524 regulating pulse width modulator contains all of the control circuit necessary to implement switching regulators of either polarity, transformer coupled DC to DC converters, transformerless polarity converters and voltage doublers, as well as other power control applications. This device includes a 5V voltage regulator capable of supplying up to 50mA to external circuit , a control amplifier, an oscillator, a pulse width modulator, a phase splitting flip-flop, dual alternating output switch transistors, and current limiting and shut-down circuit. Both the regulator output transistor and each output switch are internally current limiting and, to limit junction temperature, aninternal thermal shutdown circuit is employed. Complete PWM power control circuit Operation beyond 100KHz 2% frequency stability with temperature Total quiescent current less than 10mA Single ended or push-pull outputs Current limit amplifier provides external component protection • On-chip protection against excessive junction temperature and output current • 5V, 50mA linear regulator output available to user 16-DIP 1 Internal Block Diagram Rev. 5.0 ©2000 Fairchild Semiconductor International KA3524 Absolute Maximum Ratings Parameter Symbol Value Unit Supply Voltage VCC 40 V Reference Output Current IREF 50 mA Output Current (Each Output) IO 100 mA Oscillator Charging Current (pin 6 or 7) ICHG(OSC) 5 mA Lead Temperature (Soldering, 10 sec) TLEAD 300 °C PD 1000 mW Operating Temperature TPOR 0 ~ +70 °C Storage Temperature TSTG -65 ~ + 150 °C Power Dissipation (TA = 25°C) Electrical Characteristics (VIN=20V, f=20KHz, TA = 0 to +70°C, unless otherwise specified) Parameter Symbol Conditions Min. Typ. Max. Unit VREF - 4.6 5.0 5.4 V REFERENCE SECTION Reference Output Voltage Line Regulation ∆VREF VCC = 8V to 40V - 10 30 mV Load Regulation ∆VREF IREF = 0 mA to 20 mA - 20 50 mV Ripple Rejection RR f = 120Hz, TA = 25°C - 66 - dB Short-Circuit Output Current ISC VREF = 0, TA = 25°C - 100 - mA Temperature Stability STT - 0.3 1 % Long Term Stability ST TA = 25°C - 20 - mV/KHr CT = 0.001uF, RT = 2KΩ - 350 - KHz - OSCILLATOR SECTION Maximum Frequency f(MAX) Initial Accuracy ACCUR RT and CT constant - 5 - % Frequency Change with Voltage ∆f/∆VCC VCC = 8V to 40V, TA = 25°C - - 1 % Over operating temperature range - - 2 % Frequency Change with Temperature ∆f/∆T Clock Amplitude (Pin 3) V(CLK) TA = 25°C - 3.5 - V Clock Width (Pin 3) tW(CLK) CT = 0.01uF, TA = 25°C - 0.5 - µs ERROR AMPLIFIER SECTION VIO VCM = 2.5V - 2 10 mV Input Bias Current Input Offset Voltage IBIAS VCM = 2.5V - 2 10 µA Open Loop Voltage Gain GVO 60 80 - dB Common-Mode Input Voltage VCM TA = 25°C 1.8 - 3.4 V CMRR TA = 25°C - 70 - dB BWSS GV = 0dB, TA= 25°C - 3 - MHz 0.5 - 3.8 V Common-Mode Rejection Ratio Small Signal Bandwidth Output Voltage Swing 2 VO(ERR) - TA = 25°C KA3524 Electrical Characteristics (VIN=20V, f=20KHz, TA=0°C to +70°C, unless otherwise specified) Parameter Symbol Conditions Min. Typ. Max. Unit COMPARATOR SECTION Maximum Duty Cycle D(MAX) % Each output on Input Threshold (Pin 9) VTH1 Zero duty cycle Input Threshold (Pin 9) VTH2 Maximum duty cycle Input Bias Current IBIAS - 45 - - % - 1 - V - 3.5 - V - 1 - µA 180 200 220 mV CURRENT LIMITING SECTION Sense Voltage VSENSE V2 - V1≥50mV V9 = 2V, TA = 25°C Temperature Coefficient of Vsense ∆VSENSE/∆T - - 0.2 - mV/°C Common-Mode Voltage VCM - 0.7 - 1 V Collector-Emitter Voltage VCEO - 40 - - V Collector Leakage Current ILKG VCE = 40V - 0.1 50 µA OUTPUT SECTION (EACHOUTPUT) VCE(SAT) IC = 50mA - 1 2 V Emitter Output Voltage Saturation Voltage VE VC = 20V 17 18 - V Rise Time (10 to 90) tR RC = 2KΩ, TA = 25°C - 0.2 - µs Fall Time (90 to 10) tF RC = 2KΩ, TA = 25°C - 0.1 - µs VCC =40V, PINS 1,4,7,8,11 and 14 are grounded, V2=2V All other inputs and Outputs open - 5 10 mA Supply Current ICC 3 KA3524 Application Information Voltage Reference An internal series regulator provides a nominal 5 volt output which is used both to generate a reference voltage and is the regulated source for all the internal timing and controlling circuitry. This regulator may be bypassed for operation from a fixed 5 volt supply by connecting pins 15 and 16 together to the input voltage. In this configuration, the maximum input voltage is 6.0 volts. This reference regulator may be used as a 5 volt source for other circuitry. It will provide up to 50mA of current itself and can easily be expanded to higher current with an external PNP as shown in Figure 2. Expanded Reference Current Capability Oscillator The oscillator in the KA3524 uses an external resistor (RT) to establish a constant charging current into an external capacitor (CT), While this uses more current than a series connected PC, it provides a linear ramp voltage on the capacitor which is also used as a reference for the comparator. The charging current is equal to 3.6V/RT and should be kept within the range of approximately 30uA to 2mA, i.e., 1.8K< RT