UC2842B

AC DC Converters, Offline Switchers Overview

The UC2842B is a high-performance current mode PWM controller designed for off-line and DC-DC fixed frequency control schemes. Manufactured by UMW, it operates with a guaranteed oscillator frequency of 250kHz and supports current mode operation up to 500kHz. The device features an internally trimmed oscillator for precise duty cycle control under voltage lockout conditions. It includes a precision reference trimmed for accuracy at the error amplifier input and logic ensuring latched operation. The output stage is a high-current totem pole suitable for driving N-channel MOSFETs. Key electrical parameters include a supply voltage range of 7.6V to 30V and an operating temperature range of -25°C to 85°C.

AC DC Converters, Offline Switchers Feature Summary

• High-current totem pole output stage designed to source or sink peak currents for driving N-channel MOSFETs.
• Integrated latchable PWM comparator providing cycle-by-cycle current limit control for enhanced system safety.
• Automatic feed-forward compensation mechanism improves system stability and transient response speed.

AC DC Converters, Offline Switchers Applications

• Off-line flyback converter designs
• Forward converter topologies
• Boost DC-DC converter implementations

AC DC Converters, Offline Switchers Procurement Notes

Verify the manufacturer marking matches UMW specifications when sourcing components. Confirm the package type corresponds to the required PCB layout, typically 8-SOIC. Ensure the revision level aligns with design requirements regarding UVLO thresholds and frequency tolerances. Cross-reference datasheet revisions to confirm parameter consistency before finalizing procurement orders.

AC DC Converters, Offline Switchers Selection Notes

Select this component for applications requiring fixed-frequency current mode control with minimal external parts. The UC2842B is distinguished by its 16V on/10V off UVLO thresholds, making it ideal for standard offline power supplies. Consider alternative family members if different duty cycle ranges or lower start-up voltages are required for specific low-voltage DC-DC architectures.

AC DC Converters, Offline Switchers Part Context

This part belongs to the UC284xB family of controllers, which share common internal circuitry but differ in UVLO thresholds and maximum duty cycle capabilities. While the UC2842B supports duty cycles approaching 100%, other variants like the UC2845B utilize internal toggle flip-flops to restrict operation below 50%. This family provides a standardized solution for various isolated and non-isolated switching power supply topologies.

AC DC Converters, Offline Switchers Replacement Considerations

UC2845B: Offers identical pinout and functionality but restricts maximum duty cycle to less than 50% via an internal toggle flip-flop. Suitable for half-bridge or push-pull topologies where duty cycle limitation is necessary. Verify that the application does not require near 100% duty cycle operation when substituting.