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TPS54240: Rrt vs Switching Frequency

Part Number: TPS54240

Hi,

We got a question from the customer about TPS54240.
Could you help us?

[Question]
Is there the actual plots of Rrt vs switching frequency? They evaluated with Rrt=395.1k on EVM, then the switching frequency was 292kHz. So they want to make sure the errors between the actual switching frequency and equation value.

Schematic

SW-node waveform

Best Regards,
tateo

  • Hello Tateo,

    Equation 11 is not accurate across all frequencies. I tried equation 11 with 300 kHz and got 413 kOhms. For better results, use figures 5 and 6 in the datasheet to look up frequency expected for a given Rt value. Figure 6 shows that 300 kHz corresponds to 410 kOhms. This is close to what you are measuring.

    Regards, Robert