UC1841
UC2841
UC3841 Programmable, Off-Line, PWM Controller
FEATURES DESCRIPTION All Control, Driving, Monitoring, and
Protection Functions Included Low-current, Off-line Start Circuit Voltage Feed Forward or Current
Mode Control Guaranteed Duty Cycle Clamp The UC1841 family of PWM controllers has been designed to increase
the level of versatility while retaining all of the performance features of
the earlier UC1840 devices. While still optimized for highly-efficient bootstrapped primary-side operation in forward or flyback power converters,
the UC1841 is equally adept in implementing both low and high voltage
input DC to DC converters. Important performance features include a
low-current starting circuit, linear feed-forward for constant volt-second
operation, and compatibility with either voltage or current mode topologies. 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 1. Fault latch reset is accomplished with slow start discharge rather
than recycling the input voltage to the chip. Latch Off or Continuous Retry After
Fault 2. The External Stop input can be used for a fault delay to resist
shutdown from short duration transients. PWM Output Switch Usable to 1A
Peak Current 3. The duty-cycle clamping function has been characterized and
specified. 1% Reference Accuracy 500kHz Operation The UC1841 is characterized for -55В°C to +125В°C operation while the
UC2841 and UC3841 are designed for -25В°C to +85В°C and 0В°to +70В°C,
respectively. 18 Pin DIL Package In addition to start-up and normal regulating PWM functions, these devices include built in protection from over-voltage, under-voltage, and
over-current fault conditions with the option for either latch-off or automatic restart. …
