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LM43600: About Frequency fold back

Part Number: LM43600
Other Parts Discussed in Thread: LMR36015, LMR33630

Dear all,

I would like to know about Frequency Foldback of LM43600.

Could you answer questions below?

1.When Frequency fold back function in LM43600 is working, which does the relationship between output current and output voltage show drooping or foldback characteristic ?

2. If there is a DC-DC converter with function of foldback over-current protection, please tell me the device.

It would be great if you could let me know your thoughts on the following the question.


Best regards,

Yu Ohta

  • Yu Ohta,

    1. The frequency will fold back when the input voltage gets too close to the output voltage. The duty cycle will be approximately VOUT/VIN. Your on-time will be the duty cycle divided by the frequency. If the calculated on-time drops below ton_min (typ 200ns) then the LM43600 will fold back the frequency to maintain the necessary duty cycle. This will prevent the voltage and current from drooping.

    2. LMR33630 and LMR36015 both have a foldback feature when entering current limit.

  • Hi, Samuel

    Thank you for your reply.

    According to previous post, you introduced devices that have a fold back feature when entering current limit.
    However, I can't confirm the data about foldback feature in datasheets of LMR33630 and LMR36015.
    I need to explain about foldback feature of LMR33630 and LMR36015.
    Therefore, if you have any document or data about this, please show that to me.

    Best Regards,

  • Y.Ottey.

    App note SNVA857 page 11 goes into this in detail.