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Original question:

MC33063A: The reference design of MC33063

MC33063A: MC33063A

HD
Prodigy 140 points
Part Number: MC33063A
Other Parts Discussed in Thread: LM5157, LM5122

Hi,

I want to use this component to design a step-up converter Vin=5V to Vout=24V. But there is also a situation when the input voltage is 24V. Can this component work good if input voltage is 24V to have 24V output?

Thanks for your support.

  • 0
    TI__Guru 62565 points

    Hi HD,

    Thank you for reaching out.  This part should support 24V to 24Vout.  Like most boost controllers which has a min on time, therefore, when your Vin gets close to Vout, you may see pulse skipping but the output voltage should be regulated, just a matter of slightly increased ripple voltage. 

    On the other hand, the MC33063A is a legacy part. We have many newer boosts regulators which you may consider to use, like the latest ones LM5157 and LM51571, which are sampling now and will be fully released in a few month.  Of course you can still consider the MC33063A if it is your preference. 

    Thanks,

    Youhao Xi, Applications Engineering 

  • 0 in reply to Youhao Xi
    Prodigy 140 points

    Hi,

    thanks for the answer. So, if I have understood, the component works but not perfectly and there is more ripple and spikes on the output? Could you give me a simulation for 24Vin --> 24Vout just to see what happens? The voltage 24Vout is for supplying an array of relays so probably it is not a problem the presence of ripple and spikes... There is no boost converter that works fine in the case Vin=Vout?

    Thanks for support.

    Best Regards

    Antonio

  • 0 in reply to HD
    TI__Guru 62565 points

    Hi Antonio,

    You are right that it works but the output would have slightly increased ripples.  Simulation in such case may be different from you would actual see, but you can have some idea.  You can get the model at the following link.

    And you are right that there is basically no boost converter than works perfectly fine for  VIN=VOUT, owing to the min on time limitation. 

    Thanks

    Youhao

  • 0 in reply to Youhao Xi
    TI__Guru 62565 points

    By the way, you may take a look of our LM5122, which has  the bypass mode and it may have better performance for VIN=VOUT.

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 140 points

    Hi Youhao,

    the LM5122 is very interesting.

    Thanks for your support.

    Best Regards