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LM5022-Q1: How to disable boost circuit designed with LM5022-Q1

Chris Zhao1
Expert 1240 points
Part Number: LM5022-Q1
Other Parts Discussed in Thread: LM5022, LM5121, LM5060

Hi experts,

I have a boost designed with LM5022-Q1, I'm using the typical circuit as below.

Generally speaking it worked well so far, while I wanted to add a feature to enable/disable this boost circuit, my input 12V is always available, so I couldn't control the UVLO pin of LM5022-Q1 to achieve this, even UVLO pin is low, the output will still be about 12V.

It would be great to have my CPU to control this boost circuit, like when the control signal is high, then output is valid (54V in my board), when the input is low, then the output is 0V. 

Any suggestion?

Thanks

Chris

  • 0
    TI__Guru* 76205 points

    Hi,

    We will reply tomorrow.

    Thanks,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    TI__Guru* 76205 points

    Hi Chris,

    Thank you for using the LM5022.  Your question is about a fundamental limitation of the boost topology.  All boost converters have a  natural current path from the input to output: the diode rectifier.  

    In order to break the input from output, you can change to a different device like the LM5121.   If you want to stay with the LM5022, you can consider to add a PFET at the input line.  Pulling down the gate of the PFET to get the input power through.  Removing the pull-down, the PFET would disconnect the input line.  

    A more sophisticate solution needs a controllable hotswap device like the LM5060. 

    Thanks,

    Youhao Xi, Applications Engineering