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Original question:

LM5022: LM5022 minimum switching frequency

LM5022: About operation at switching frequency 200kHz or less

Y.Ottey
Mastermind 6145 points
Part Number: LM5022

Dear TI Team

My customer is considering using the LM5022 with a switching frequency of 75kHz.
Regarding the above, I would like to ask the following questions.

1. From the following post, it is stated that the minimum switching frequency is not set and it can be used even at 70kHz.
https://e2e.ti.com/support/power-management/f/power-management-forum/866827/lm5022-lm5022-minimum-switching-frequency?tisearch=e2e-sitesearch&keymatch=LM5022%25252520frequency

However, when I tried to simulate the switching frequency at 70kHz with WEBENCH, I could not set it below 200kHz.

Does this mean that TI has not confirmed the operation below 200kHz, so simulation is not possible?
(Although the data sheet states that the LM5022 has a maximum switching frequency of 2.2MHz, WEBENCH only supports up to 600kHz.)

2. When RT is set at a switching frequency of 75kHz, the data sheet is calculated to be approximately 230kΩ.
However, in the data sheet, as shown in the figure below, there is only data with frequencies higher than 200kHz.
Is there any problem in calculating RT by the formula in the data sheet when using it at a switching frequency of 75kHz?

Best Regards,
Y.Ottey

  • 0
    TI__Expert 7450 points

    Hi Y.Ottey,

    Thank you for choosing LM5022.

    I'll confirm this with our designer and let you know.

    Thanks,

    Yinsong

  • 0
    TI__Expert 7450 points

    Hi Y.Ottey,

    Thank you for your patience. The controller may still work at around 70kHz but the switching frequency in the datasheet is only characterized down to 200kHz. It is not recommended and the performance is not guaranteed. It is not common to have such low frequency design for switch mode power supply but they can still make their own decision whether to implement it or not.

    Thanks,

    Yinsong