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BQ25570: V_OUT issue

Part Number: BQ25570


We are using BQ25570 on our design, and we are noticing a very strange issue.

If v_bat is powered from a supercapacitor (~3.5v up to 4.0), regulated output is only ~0.6V instead of 1.8v. If v_bat is powered from a regulated power source (3.3V from usb), then v_out shows the expected output of 1.8v.

For some reason v_out is only 0.6v if powered from a supercacitor, and correct 1.8v if powered from regulated usb hub. Any idea why this might be the case?

  • Hello,

    For further context, can you please answer the following questions:

    - What capacitance is the supercap which you are using?

    - What is VSTOR, VBAT, VIN_DC, and VOUT both with a regulated power source and the super capacitor?

    - If possible, can you please provide a waveform for VBATT, LBUCK, VOUT when the supercapacitor is applied?

    - If possible can you provide a current reading or waveform from the supercapacitor when VOUT is at 0.6V?

    Best Regards,

    Juan Ospina