BQ25895: what's the refresh threshold for BTST?

Howard Zou

Genius 12365 points

Part Number: BQ25895

Hi,

in the datasheet Vbtst-Vsw will be compared with Vbtst_refresh.

But I can't find the value of Vbtst_refresh.

My customer observe VBUS=4.3V when adaptor is removed, and the battery is 4.1V.

If we short VBUS to GND with a 1k resistor and then release VBUS floating, VBUS will be 0V and can't go back to 4.3V.

I guess it's uncontrolled boost back from battery to VBUS.

over 6 years ago

0 Ricardo over 6 years ago

TI__Genius 10385 points

Howard,

Do you mind sharing the schematic?

Thanks,

Ricardo

0 Ricardo over 6 years ago

TI__Genius 10385 points

Howard,

I specifically would want to know the DC bias voltage rating of the bootstrap capacitor and what the VINDPM setting is.

Thanks,

Ricardo

0 Howard Zou over 6 years ago in reply to Ricardo

TI__Genius 12365 points

Ricardo,

the schematic is as below: the bootstrap capacitor is 47nF, 16V.

when absolute VINDPM=4.4V, VBUS is 4.4V when unplug the adaptor, and the incidence probability is about 1/100. It's hard to reproduce the wrong phenomenon.

when absolute VINDPM=3.9V, VBUS is 4.4V when unplug the adaptor, and the incidence probability is more than 50/100. It's very easy to reproduce the wrong phenomenon.

0 Ricardo over 6 years ago in reply to Howard Zou

TI__Genius 10385 points

Howard,

I am concerned that the bootstrap capacitor only has a DC bias rating of 16V. Try a capacitor rated for 25V. If possible, keep VINDPM at 4.4 V or increase it further. Let me know if this helps.

Thanks,

Ricardo

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BQ25895: what's the refresh threshold for BTST?