DESCRIPTION

· The UC1851 family of PWM controllers are optimized for off-line primary side control.
· Includes a high current totem pole output stage and a toggle flip-flop for absolute 50% duty cycle limiting.
· Pin for pin compatible with the UC1841 series.
· Packaged in 18-pin plastic or ceramic dual-in-line packages, or 20 Pin PLCC for surface mount applications.
· Characterized for operation from -55 °C to +125 °C (UC1851), -40 °C to +85 °C (UC2851), and 0 °C to +70 °C (UC3851).

FEATURES

· All control, driving, monitoring, and protection functions included.
· Low-current off-line start circuit.
· Voltage feed forward or current mode control.
· High current totem pole output.
· 50% absolute max duty cycle.
· PWM latch for single pulse per period.
· Pulse-by-pulse current limiting plus shutdown for over-current fault.
· No start-up or shutdown transients.
· Slow turn-on both initially and after fault shutdown.
· Shutdown upon over or under voltage sensing.
· Latch off or continuous retry after fault.
· 1% reference accuracy.
· 500kHz operation.

APPLICATIONS

· Ideal for cost-sensitive applications due to inclusion of all major housekeeping functions.
· Suitable for constant volt-second operation with linear feed-forward.
· Compatible with both voltage or current mode control.
· Programmable start threshold, over-voltage, under-voltage, and over current fault thresholds.
· Configurable fault latch for automatic restart or latched off response to a fault.