KA3845

KA3842/43/44/45 Inv № 59 Current Mode PWM Controller July 1995 - revised July 2002 DESCRIPTION KA3842/43/44/45 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 UC3842A(AM) and UC3844A(AM) have UVLO thresholds of 16 V (on) and 10 V (off). The corresponding thresholds for the UC3843A(AM)/45A(AM) are 8.4V (on) and 7.6V (off). The UC3842A(AM) and UC3843A(AM) can operate within 100% duty cycle. The UC3844A(AM) and UC3845A(AM) can operate within 50% duty cycle. The UC384XA(AM) 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 300KHz (384XA) 500KHz (384XAM) BLOCK DIAGRAM (toggle flip flop used only in UC3844, UC3845) PIN CONNECTION (TOP VIEW) 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 s...