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BQ25504: BQ25504 Boost swtich frequency

kevin.huang_FJXM
Expert 2925 points
Part Number: BQ25504

Hi teams:

Solar charging chip bq2504. The specification describes that the maximum boost swtich frequency is 1MHz.

When the chip works, the output voltage is adjusted through PFM mode.

Ask:

1. How does the chip control the boost operating frequency?

2. We set Vbat_ OV = 4.5V, what is the current working frequency?

3. Can I set the minimum and maximum operating frequency? How?

  • 0
    TI__Guru**** 154236 points

    Hi Kevin,

    The boost converter is hysteretic and uses pulse frequency modulation (PFM).  In short, a comparator monitoring the output voltage, that is below VBAT_OV, turns on the low side power FET while the input voltage is not below VMPP.  The FET stays on until the inductor current reaches IIN(dc) =200mA typical.  The FET cannot come back on until the input capacitor as recharged above VMPP. So, the switching action comes in somewhat unpredictable pulses.  The switching frequency cannot be set.

    Regards,

    Jeff