BQ24163 won't stay in "Charge Complete" state

Brady Hurlburt

Other Parts Discussed in Thread: BQ24163

We are using the BQ24163 charger chip in our design, and we are having an issue when we read the STAT (Register 00 bits B6-B4).

We connect power to the IN input and a battery that is fully charged. We can see with a current probe that the current going into the battery is less that the termination current ITERM we have set (Register 05 bits B2-B0, set to the maximum 400mA). We then read STAT once per second, expected to see "Charge complete" every time. However, we see that it toggles randomly between "Charge Complete", "Charging" and "IN Ready".

We have also noticed that even when toggling between these states, at no time does BGATE go low.

We purchased the development board for this chip and connected it to our system with the same register settings we were using, and we see the same behavior.

Below, I've listed the state of all the registers when we read STAT. Has anyone experienced any similar issues with this chip? Or, do you see anything incorrect about our register settings below?

Status 0x10
Supply status 0x30
Control 0x8c
Battery voltage 0x8e
Vender 0x45
Battery termination 0xb7
Vin-dpm 0x00
Safety timer 0x78

over 9 years ago

0 Jeff F over 9 years ago

TI__Guru**** 155296 points

To enter charge complete, the battery charger current has to stay below the termination current for 32ms. Fast rising, high duty cycle SYS transients of longer than 32ms can cause the IC to enter supplement mode and exit charge complete, however, BGATE should go low. Are you seeing a squarish waveform on SYS as shown in datasheet figure 16?

0 Brady Hurlburt over 9 years ago in reply to Jeff F

Prodigy 90 points

Hi Jeff,

Thanks for the reply! We had suspected that transients were violating the 32ms period. However, we see this issue even when VSYS is completely disconnected from the system. So, in that case, VSYS is completely flat.

Any other thoughts?

Thanks,

Brady

0 Jeff F over 9 years ago in reply to Brady Hurlburt

TI__Guru**** 155296 points

Can you send scope shots of V(BAT), V(SYS), I(BAT) and I(SYS) when this is happening?

0 Allison Pluger over 9 years ago in reply to Jeff F

Prodigy 60 points

Hello Jeff,

I'm working with Brady on debugging our problem.

Here is a scope capture of a situation when the erratic behavior occurs. The short pulses correlate to the "IN Ready" state, the longer bit in the middle and at the right side of the capture correlate to the "Charging" state, and the flat parts correlate to the "Charge Complete" state.

Here is a capture of the rising edge of a "IN Ready" pulse. In this capture, V(BAT) and V(SYS) have offsets of 4 V.

Thank you,

Allison

0 Jeff F over 9 years ago in reply to Allison Pluger

TI__Guru**** 155296 points

Can you add the battery current to the plots?

0 Allison Pluger over 9 years ago in reply to Jeff F

Prodigy 60 points

Jeff,

I accidentally mislabeled the scope plots. The I(SYS) on the plots is actually I(BAT).

Sorry,
Allison

0 Jeff F over 9 years ago in reply to Allison Pluger

TI__Guru**** 155296 points

There are short, fast pulses coming out of the battery so SYS must be pulling current from the battery.

0 Allison Pluger over 9 years ago in reply to Jeff F

Prodigy 60 points

Why would the system be pulling current out of the battery instead of the AC power?

Thanks,

Allison

0 Jeff F over 9 years ago in reply to Allison Pluger

TI__Guru**** 155296 points

Supplement mode is faster than the transient response of the SYS output. In other words, fast transients will come out of the SYS caps, BAT caps and the battery itself until the SYS buck converter's feedback loop can respond.

0 Allison Pluger over 9 years ago in reply to Jeff F

Prodigy 60 points

Why do you think BGATE is never turning off? Even when the chip returns "Charge Complete", BGATE is always high.

Also, here is a snippet of the design showing how the chip is connected. Do you see anything wrong here?

Thanks for all your help,

Allison

0 Jeff F over 9 years ago in reply to Allison Pluger

TI__Guru**** 155296 points

BGATE only goes low to turn on the Q18 during HiZ mode, not supplement mode. I misspoke in an earlier post. The schematic looks okay except for the capacitance on SYS. I assume there is additional capacitance on the SYS rail that is not shown on the schematic?

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BQ24163 won't stay in "Charge Complete" state