UC3842N Current-Mode PWM Controller

The UC3842 is available in an 8-Pin mini-DIP the necessary features to implement off-line, fixed-frequency current-mode control schemes with minimal external parts count. This technique results
in improved line regulation, enhanced load response characteristics, and a simpler, easier to design control loop. Topological advantages include inherent pulse-by-pulse current limiting. Protection circuitry includes built-in under-voltage lock-out and current limiting. Other features include fully-latched operation, a 1% trimmed bandgap reference, and a start-up current less than 1mA. These devices feature a totem-pole output designed to source and sink high peak current from a capacitive load, such as the gate of a power MOSFET. Consistent with N-channel power devices, the output is low in the OFF-state.

Features/Specs:

Low start-up current (≤1mA)
Automatic feed-forward compensation
Pulse-by-pulse current limiting
Enhanced load response characteristics
Undervoltage lock-out with hysteresis
Double pulse suppression
High current totem-pole output
Internally-trimmed bandgap reference
400kHz operation, guaranteed min

APPLICATIONS
• Off-line switched-mode power supplies
• DC-to-DC converters UC3842

NOTES:
1. All voltages are with respect to Pin 5; all currents are positive into the specified terminal.
2. See section in application note on “Power Dissipation Calculation”.
3. This parameter is guaranteed, but not 100% tested in production.