BQ25730: AD not always working

Hi Joseph,

Did you enable ADC_START bit in ADC Options register 0x3A? First enable ADC channel, then enable ADC_START bit to start the ADC conversion. 

Regards,

Tiger

Here is a register dump from when the AD is not working.

00 3206 0000 5208 09c4 3c00 0000 7300 2000
10 ffff ffff ffff ffff ffff ffff ffff ffff
20 8000 b880 2000 2100 0000 0000 6e6d d540
30 3f00 00b7 0428 4a81 4020 605f 1848 006c

You can see that the start is enabled and channels are selected. I think during chip initialization I do this in one step, does it need to be a 2 step process of selecting channels before selecting start? You cannot do bit writes so any time the start bit is written the channel bits must also be written. 

More info:

When the BQ25730 is in this state of the AD not working, doing a reset bit 4000h in 34/35h does not help and cycling the EN_LPWR charge option 0 (00/01h) register does not help recover operation. 

So currently I have no way to recover the operation by SW.

More info:

Regen is at 6V when AD is not working

Tried the ADC channel config before the ADC start and still have the same problem in 1 out of 100(?) times the ADC is not starting correctly.

Hi Joseph,

Note that it may take about tens of millisecond for the ADC conversion. I would suggest adding a delay to allow the ADC complete, or checking whether ADC complete before reading. 

Regards,

Tiger

The data sheet says 25msec per conversion. The SW is requesting 6 conversions and waits 200msecs after the start to read.

Is there a limit to how frequently you can do a conversion? The SW is starting a new conversion every 200 msecs.

Thanks

Hi Joseph,

I think so.  A total of 8 channels shares the same ADC through MUX.  Did you encounter the same issue if a new conversion every 1 second?

Regards,

Tiger

I did not try the one shot at 1/sec. We are desperate for a solution so I just changed to the auto/periodic conversion and so far that has not locked up the AD.It takes a lot of time to reproduce so it is going to take some time to confirm a solution.

The SW only uses 6 channels and at 25msecs each that should be 150msecs. So every 200msecs should be giving margin.

My suggestion is to start with more time and tight up the cycle time. 

It has taken longer to reproduce the problem now that I am using AD auto convert mode, but the problem is still present.

Steps:

1) Device runs till battery is at 0%

2) SW shuts device down and enters low power mode

3) External power is applied.

4) AC_STAT and CHRG_OK both indicate external power is present.

5) SW configures device to exit low power mode

6) A/D does not start.

SW Attempts to use register reset, toggle low power mode and write 0 to the fault flag register do not bring device back up. The SW can detect it is in this fault mode but is not able to get the AD to start running.

Hi Joseph,

Could you list the test conditions such as VBAT=? VBUS=?, CELL=?

Regards,

Tiger

Vbat: Design supports both 4s and 5s, currently all of the testing is 4s so 12V - 16.8V

Vbus is 24V

Cell is Li-ion

Sorry, we could not duplicate this.

• Apply 24V on the bus input
• Apply 13V on the battery terminal
• Enable VBAT, VSYS and other channels
• Set ADC_CONV every 1 second
• Enable ADC_START.

When I adjust the VBAT up and down, the VBAT and VSYS ADC registers 0x2C follow and update. 

BTW, when external supply is available, the LOW_POWER_MODE bit is ignored. 

Regards,

Tiger

for us this is only happening maybe 1 out of several 100 times.

Hi Joseph,

I hope re-starting ADC or restarting the charger helps. 

Regards,

Tiger

The only solution we have found is to remove external power and sometimes it also requires removal of the battery. Reset, low power mode, etc do not clear this condition.  The removal of the battery is not easy since the unit is in a case.