BQ25895: BATFET disabled on battery insertion

Hi Jochem,

1.What's the yellow waveform?

2. Is any load connected at SYS pin?

Thanks,

Ning

Hi Ning,

Ah yes, asking two questions right after each other isn't the best thing to do. Here are the answers;

1. The yellow waveform is connected to a TPS3897's SENSE_OUT. It has a sense delay of 5 seconds, so the first 5 seconds, the circuit is only powered up but nothing else is happening (as the microcontroller hasn't booted yet).

2. Yes, VSYS is used directly as input for the 3.3V LDO of which you can see the output in the blue waveform. PMID is connected to an amplifier, but isn't yet enabled because the microcontroller hasn't booted yet. The amplifier is powered down, so will draw very little (sub-mA) current.

I managed to get both situations in the same window. Please note that I didn't give attempt #1 the full 5 seconds, but there's no 3.3V, so the TPS3897 is out of the equation. On second connect of the battery (#2), 3.3V remains live and after the 5 seconds, the SENSE_OUT becomes high as well.

Best regards,

Jochem

Hi Jochem,

We are checking and will get back to you soon.

Thanks,

Ning

Hi Jochem,

What are BQ25895 VBUS (voltage at VBUS pin), IVBUS, VBAT (voltage at BAT pin), IBAT, VSYS, ISYS under the condition?

Thanks,

Ning

Hi Ning,

I've attached two screenshots from the PPK-II that's set to output 3500mV and functions as VBAT. I've also attached two oscilloscope screenshots. The filenames of the PPK-II screenshots, highlight to which oscilloscope file they are linked.

Oscilloscope screenshot 14 shows a weird situation where VBUS also registers a voltage, while nothing is connected.

Yellow is VBAT, blue is VSYS and purple is VBUS.

Best regards,

Jochem

Correct situation

BATFET disable situation

VBUS weirdness

Hi Jochem,

For BATFET disable situation, the battery discharge current was up to 60mA?

Thanks,

Ning.

Hi Ning,

Yes, that's the case. That's the microcontrollers bootloader stage.

Best regards,

Jochem

Hi Jochem,

1.May one unit show all 3 behaviors or one unit only shows one behavior?

2. Did you notice one unit behavior abnormally?

Thanks,

Ning

Hi Ning,

1. All screenshots above are measurements taken from one single DUT, but all three prototypes show the same behaviour.

2. Apart from the behaviour above, all units work as they should. 

Best regards,

Jochem

Hi Jochem,

Do you mean that only one unit behaves abnormally?

Thanks,

Ning.

Hi Ning,

No I don't. 

Jochem van Kranenburg said:

all three prototypes show the same behaviour.

Best,

Jochem

Hi,

If only one unit behaves abnormal, it might get damaged. Please try another fresh unit.

Thanks,

Ning

Hi Ning,

I don't know what to say. Please read my last two replies carefully. Let me rephrase; ALL units behave abnormally. They have been doing so since delivery. They have been manufactured according to the specifications.

Best regards,

Jochem

Hi Jochem,

Did you test on multiple boards or one board for all the units?

Thanks,

Ning

Multiple

Hi,

Did you tested on your own board or on the EVM?

Thanks,

Ning