UC3842A

Current Mode PWM Controller application INFO available UC1842A/3A/4A/5A UC2842A/3A/4A/5A UC3842A/3A/4A/5A FEATURES Optimized for Off-line and DC to DC Converters Low Start Up Current (<0.5mA) Trimmed Oscillator Discharge Current Automatic Feed Forward Compensation Pulse-by-Pulse Current Limiting Enhanced Load Response Characteristics DESCRIPTION The UC1842A/3A/4A/5A family of control ICs is a pin for pin compatible improved version of the UC3842/3/4/5 family. Providing the necessary features to control current mode switched mode power supplies, this family has the following improved features. Start up current is guaranteed to be less than 0.5mA. Oscillator discharge is trimmed to 8.3mA. During under voltage lockout, the output stage can sink at least 10mA at less than 1.2V for VCC over 5V. The difference between members of this family are shown in the table below. Under-Voltage Lockout With Hysteresis Double Pulse Suppression High Current Totem Pole Output Internally Trimmed Bandgap Reference 500kHz Operation Low RO Error Amp Part # UC1842A UC1843A UC1844A UC1845A UVLO On 16.0V 8.5V 16.0V 8.5V UVLO Off 10.0V 7.9V 10.0V 7.9V Maximum Duty Cycle <100% <100% <50% <50% BLOCK DIAGRAM Note 1: A/B A = DIL-8 Pin Number. B = SO-14 Pin Number. Note 2: Toggle flip flop used only in 1844A and 1845A. SLUS224A - SEPTEMBER 1994 - REVISED APRIL 2002 CONNECTION DIAGRAMS ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (Low Impedance Source) . . . . . . . ....