BQ24232: IC not entering charge mode - 0 charge current and ISET at 0V

Hi Alex,

Would you be able to take the fault IC and put it on a board that was not showing the behavior? We typically refer to this as an ABA swap and we want to see if the behavior that you're observing (not charging) is following the IC or the board. 

By chance, do you have some sort of datalog showing the device behavior over time?

Best Regards,

Anthony Pham

Hi Anthony,
I have tried the ABA swap and the behavior is dependent on the board and not the IC. I have 3 boards with me, #1 has a working charger and #2 and #3 do not work.
An IC working on board #1 was not working on #2 and #3, while the ICs not working on #2 and #3 worked on #1.
I have measured all resistors around the IC and the values are all correct, and no trace seems to be broken. Any idea what the issue could be?

Unfortunately I do not have any datalog.

Thank you,
Alex

Here are current waveforms for a working and a problematic board on IN power input power up (5V). The behavior is quite similar but after around 30ms, charging is interrupted on the problematic board. Note : negative current is current flowing into the battery.

Some modifications were made to the board by changing ISet resistor value to 10kOhm and putting the faulty board into USB100 mode, which did not change the behavior. In this case, we saw positive current spikes occasionally on one of the faulty boards, as can be seen in the images below.


Finally, I also tried with TMR and ITERM pins not floating (Rtmr = 47kOhm and Riterm = 10kOhm), but the current waveform on IN power up was identical to that of the faulty board above.

Any suggestions on how to fix this issue?

Thank you,
Alex

Hi Alex,

A reason where the battery may be sourcing current would be supplement mode because of a low OUT voltage. That looks like it may be the case there as I notice a small difference in the OUT waveform images you've provided. 

The resistors on the device shouldn't have any impact here and I do believe they are correct. Is there a change you'd be willing to try checking the capacitors on the OUT pin? I don't quite see the capacitors on your schematic. For curiousity's sake, can you try adding some capacitance on the OUT pin of the problematic device?

Best Regards,

Anthony Pham

Hello Anthony, 

Thanks for the reply, here is a screenshot including the capacitors, sorry about that (note that for now the NTC connector is not used and the resistance R30 is installed).
I have tried with an added 22uF and with no capacitance at all with the same results. I have also tried with a 100mA load placed on OUT and we observe the same behavior with the faulty charger as you can see.





I have ordered new ICs to see if maybe this will solve the problem and will be receiving a new batch of boards soon so I can identify if it is an assembly problem. In the meantime do you have any other possible ideas of what is happening here?

Thank you for your help

Hi Alex,

Looking forward to seeing if new ICs shed some light on this. I did notice that when you see fast charge, it happens for about 25 ms before stopping This happens to match up with the deglitch time for termination being detected. I'm wondering if you see this only when the battery is close to the battery regulation voltage? What if you use a battery that's about 3.7 V?

Best Regards,

Anthony Pham

Hi Anthony,

No luck with the new ICs. I also tried multiple batteries with different voltages (including 3.5V and 3.7V) with the same results unfortunately.
My intuition is also that this has to do with charger termination, but I can't seem to identify why it is being detected.

Thanks, 
Alex

Hi Alex,

This sounds like a system level observation that isn't rooted from the BQ24232 since you've tried it with fresh new ICs. I'm wondering if you go and try disconnecting your load on IOUT to at least isolate the BQ24232 portion of the schematic if you'll see the same thing.

Best Regards,

Anthony Pham

Hi Anthony, I tried disconnecting the load with the same result.