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BQ25713: No load behavior

Shaquille Chen
Intellectual 1770 points
Part Number: BQ25713

Hi Team,

Customer feedback that BQ25713 at pure buck or boost mode have different behavior on different load.

For example:

In pure boost mode, Q1 should always on. But we found Q1 will turn on at no load but always on by 500mA load.

No load Q1 Vgs:

0.5A load Q1 Vgs:

  • 0
    TI__Expert 5330 points

    Hi Shaquille,

    I believe that the device is entering PFM operation when you cross below 500 mA.  You can refer to section 9.3.5.3 of the datasheet.  Also, if you look at figure 46 in the datasheet, you can see SW1 and SW2 in PFM.  During the periods where the inductor current would have fallen below 0, both of the low-side FETs turn on and you see that both switch nodes drop to GND. 

    The point for entering PFM depends on Inductor ripple current, but 500 mA is about the point I would expect.  You should see that as current is decreased further below the 500 mA level, the periods of SW1 at GND widen.  This is expected operation.

    Regards,

    Steve