UC3842

www.fairchildsemi.com UC3842/UC3843/UC3844/UC3845 SMPS Controller Features Low Start up Current Maximum Duty Clamp UVLO With Hysteresis Operating Frequency up to 500KHz Description The UC3842/UC3843/UC3844/UC3845 are fixed frequencycurrent-mode PWM controller. They are specially designed for Off-Line and DC to DC converter applications with minimum external components. These integrated circuits feature 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 for driving a Power MOSFET. The UC3842 and UC3844 have UVLO thresholds of 16V (on) and 10V (off). The UC3843 and UC3845 are 8.5V(on) and 7.9V (off). The UC3842 and UC3843 can operate within 100% duty cycle. The UC3844 and UC3845 can operate with 50% duty cycle. 8-DIP 8-SOP 1 1 14-SOP 1 Internal Block Diagram * NORMALLY 8DIP/8SOP PIN NO. * ( ) IS 14SOP PINNO. * TOGGLE FLIP FLOP USED ONLY IN UC3844, UC3845 Rev. 1.0.1 ©2002 Fairchild Semiconductor Corporation UC3842/UC3843/UC3844/UC3845 Absolute Maximum Ratings Parameter Supply Voltage Output Current Analog Inputs (Pin 2.3) Error Amp Output Sink Current Power Dissipation at TA≤25°C (8DIP) Power Dissipation at TA≤25°C (8SOP) Power Dissipation at TA≤25°C (14SOP) Storage Temperature Range Lead Temperature (Soldering, 10sec) Symbol VCC IO V(ANA) ISINK (E.A) PD(Note1,2) PD(Note1,2) PD(Note1,2) TSTG TLEAD Value 30 ±1 -0.3 to 6.3 10 1200 460 ...