KA3843B

AC DC Converters, Offline Switchers Overview

The KA3843B is a fixed-frequency current-mode PWM controller designed for offline and DC-to-DC converter applications. It features a trimmed oscillator, temperature-compensated reference, high-gain error amplifier, and current sensing comparator. The device includes a high-current totem-pole output suitable for driving power MOSFETs. Key electrical parameters include a maximum switching frequency of 500 kHz, a startup voltage of 16 V, and a supply voltage range of 12 V to 25 V. The duty cycle is clamped at 97%, and it operates within a temperature range of 0°C to 70°C.

AC DC Converters, Offline Switchers Feature Summary

• Fixed-frequency current-mode PWM control architecture
• Integrated trimmed oscillator and temperature-compensated reference
• High-current totem-pole output stage for direct MOSFET drive
• Built-in current sensing comparator and high-gain error amplifier

AC DC Converters, Offline Switchers Applications

• Offline flyback converters
• Forward converters
• DC-to-DC step-down converters

AC DC Converters, Offline Switchers Procurement Notes

Verify the specific suffix 'B' indicates commercial grade performance and standard operating temperature range. Confirm package type matches 8-DIP requirements. Check RoHS compliance status against current manufacturing standards. Ensure supplier documentation aligns with Fairchild Semiconductor specifications.

AC DC Converters, Offline Switchers Selection Notes

Select this component for designs requiring precise duty cycle control and efficient power management in isolated topologies. The integrated features reduce external component count. Ensure input voltage stays within the 12 V to 25 V range during operation. Verify thermal constraints fit the 0°C to 70°C operational window.

AC DC Converters, Offline Switchers Part Context

Part of the KA384x family of current-mode controllers. Shares functional similarities with UC3842 series devices. Designed as a drop-in replacement for legacy controllers in many offline power supply designs. Manufactured by Fairchild Semiconductor, now part of ON Semiconductor.

AC DC Converters, Offline Switchers Replacement Considerations

UC3842B is a pin-compatible alternative from Texas Instruments. Verify electrical parameter compatibility before substitution. Check package dimensions and thermal characteristics match the original design requirements.