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TPS57114-Q1 switching frequency for PMP10652

Other Parts Discussed in Thread: PMP10652

I would like to confirm TPS57114-Q1 switching frequency for PMP10652.

In "Description", there is the comment "TPS57114Q1 is used to provide power to the cores and it is a high current 

2,2MHz switching buck converter." 

But in the datasheet, TPS57114-Q1 switching frequency is up to 2MHz.

Which is correct? Are there any method for TPS57114-Q1 with 2.2MHz switching frequency?

Best regards,

Atsushi Yamauchi

  • Hello Yamauchi-san,

    I've assigned this post to the appropriate applications engineer. He will respond to your questions.

  • Hello Yamauchi-san,

    I looked at PMP10652 schematic diagram and found that actual switching frequency used is around 1.95 MHz which is ok for according to datasheet. In the description, may be they have specified it as 2.2 MHz by mistake. Report also shows that they are passing CISPR25 EMC requirements also and i think you are safe to use this switching frequency.

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  • Dear Murthy-san,

    Thank you for your reply.

    We are searching the business, so we don't have the active project. And I want to check this system for the customer support.

    I have questions for your reply.

    1. When the switching frequency set 1.95MHz (R=84.5kohm in schematic), how much is the variation of the frequency?

        Is there possibility of AM band (< 1.6MHz)?

    2. I understood the mistake of the frequency (not 2.2MHz). But in the website for this reference design, there is the description

       "All devices Switching frequency at 2.1MHz (AM Band Avoidance)". Is this the mistake too?

        If this is the mistake, how do you select the devices? I suggest the switching frequency of TPS57114-Q1 may be lower than 1.6MHz by

       the variation (can not avoid AM band), and I would like to know your concept for this reference design.

    3. If the switching frequency is lower than 1.6MHz (by the variation) or the frequency of low side for the variation, are they passing CISPR25?

        If they are not passing CISPR25 with low switching frequency by the variation (ex. 1.55MHz, 1.6MHz and so on), I think TPS57114-Q1 can not be used

      (promoted) for this application. 

    Could you please reply them?

    Best regards,

    Atsushi Yamauchi

  • Hello Yamauchi-san,

    See my comments below:

    1. Typically switching frequency is very close to the set frequency and in the worst case it can be +/- 20%. Since EMC measurements are done at room temp in normal lab conditions and usually customers do not see so much issues with it and so far nobody complained to us on this. The main reason for 2 MHz operation is to avoid the AM band frequency and many automotive customers are using this part. If some one needs very precise clock accuracy, then they use external clock and with external clock, device sync's very well and PLL accuracy is usually very good (+/-5%).

    2. PMP10652 shows that they passed CISPR25 with 2 MHZ switching frequency. This reference design was done by different team and I have requested them to make the corrections with respect to switching frequency.

    3. We haven't tested whether device will pass CISPR25 if the switching frequency is set to 1.6 MHz.