Current Mode PWM Controller
• Optimized for Off-line and DC to DC
• Low Start Up Current (<0.5mA)
• Trimmed Oscillator Discharge Current
• Automatic Feed Forward Compensation
• Pulse-by-Pulse Current Limiting
• Enhanced Load Response Characteristics
The UC1842A/3A/4A/5A family of control ICs is a pin for pin compati-
ble improved version of the UC3842/3/4/5 family. Providing the nec-
essary features to control current mode switched mode power
supplies, this family has the following improved features. Start up cur-
rent 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
• Under-Voltage Lockout With Hysteresis
• Double Pulse Suppression
• High Current Totem Pole Output
• Internally Trimmed Bandgap Reference
• 500kHz Operation
• Low RO Error Amp
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