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BQ24800: Minimum off-time

Part Number: BQ24800
Other Parts Discussed in Thread: BQ24780S,

Hi, Support team

When I confirmed the minimum off-time using BQ24800EVM, it is approximately 50ns under default register setting.

What is it by design?

Thanks

Tamio

  • Hi Tamio,

    There is not a set design value for the minimum HSFET off time. The HSFET off time is a function of several operating conditions, such as the switching frequency and the duty cycle. The sleep comparator requires a minimum difference between the input voltage and the output voltage, and thus sets a practical limit to the maximum duty cycle. The analysis is very similar to this E2E thread (although the sleep comparator thresholds are a bit different from the BQ24780S):

    https://e2e.ti.com/support/power-management/f/196/p/780090/2885213

     A 50 ns HSFET off time sounds reasonable, but we can confirm this with a calculation if you have more information about the operating conditions. When you tested the BQ24800 EVM, what were the input voltage and output voltage? Also, the switching frequency was set to the default value of 800 kHz, correct?

    Best regards,

    Angelo