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UC3846: Pull a wire from the load to pin 6 of the chip. What is this for?

Qi Liu
Expert 3080 points
Part Number: UC3846
Other Parts Discussed in Thread: TL431

Hi support team,

My custerm has a question as follow:

Pull a wire from the load to pin 6 of the chip. What is this for? Voltage feedback?
Could you give a detailed description?

Thanks so much.

Best regards,
Yuki

  • +1
    TI__Mastermind 27715 points

    Hi Qi,

    The "wire" you are asking about is a simplified representation showing the sensed output voltage feedback, divided down by 3.6kΩ and 3.2kΩ. This diagram is simplified to highlight the most important external components needed around the PWM. One thing you should immediately notice is that direct sensing of the output voltage this way violates the isolation provided by the transformer. In a real isolated converter application, the feedback signal needs to be isolated secondary to primary and this is commonly accomplished using an optocoupler+TL431.

    Regards,

    Steve M