The project used UC3843 with 12V power supply. Now the power supply is changed to 5V, So IC changed to UCC 3803.Only the IC is changed, and the peripheral circuit is not changed, The Circuit as follows:
1>When used 5V power supply, The output of the sixth pin is abnormal, and the third pin is the waveform above, the waveform as follows:
2>When used 5.5V power supply, The output of the sixth pin is normal,the waveform as follows:
3>There is a board, the input voltage must reach 8.5V, and the sixth pin can be switched normally,the waveform as follows:
4>modify the working frequency from 100K to more than 900 K,the output of the sixth pin is abnormal,the waveform as follows:
Johnsin Tao:
HI
两个芯片是由差别的,不能直接取代,不仅仅是供电的问题,你可以再UC3843电路的基础上改,结合如下文档:
DN-42A Design Considerations for Transitioning from UC3842 to the New UCC3802