BQ25101: charge current and nCHG status at the time of Cold Fault state and recovery from it

murakami yusaku

Part Number: BQ25101

Hi.

I have configured a power supply circuit using this charging IC for mobile devices.

As one of the evaluations, I was checking the charge control according to fig.20, but there were some points that I did not get it.

When the TS voltage reached vcold state.2, the charging current stopped but the LED remained on. Is this correct?
When I returned to the Vcool state.3, charging resumed, but the charging current did not reach the target value. Moreover, the LED was turned off. Why is this?
Once the hardware was reset, it returned to the intended operation state.4. Does it mean that a hard reset is required to return from the Cold Fault to state.4?

I would be grateful if you could give me some advice.

best regards.

state.1

Vcool

state.2

Vcold

state.3

Vcool

hard reset

state.4

Vcool

LED

(nCHG open drain FET)

OFF

BATT charge current

50% Ichg.

OFF

but unstable.

unless 50% Ichg.

OFF

50% Ichg.

over 2 years ago

0 Nick Brylski over 2 years ago

TI__Mastermind 19195 points

Hi Murakami,

I’m taking a look into this you can expect to hear back early next week.

thanks,

Nick

0 Jackson DiGiovanna over 2 years ago

TI__Expert 8245 points

Hi Murakami,

I have tested this behavior in the lab and noticed some differences from the behavior you are seeing. Using the BQ25101 EVM I was able to recreate states 1-5 but the LED remained on for me the entire time.

To answer your questions more clearly,

1. This is indeed the behavior I observed on the bench. At Vcold, the device stops charging but the LED remains on.

2. When transitioning to Vcool from Vcold, the device returned to normal operation at 50% ICHG as expected and the LED remained on.

3. I was able to recover no problem from Vcold back to Vcool without a full hardware reset.

To summarize, I am not sure why this behavior after Vcold is occurring in your case but it is not what is expected and not what I am seeing on the bench.

0 murakami yusaku over 2 years ago in reply to Jackson DiGiovanna

Prodigy 10 points

Nick san, Jackson san

Thank you for testing. i will check item 2 again. Please let me know if you have any idea that item 2 may occur.

best regards.

0 Nick Brylski over 2 years ago in reply to murakami yusaku

TI__Mastermind 19195 points

Hi Murakami,

Can you share waveforms of IN, OUT, and TS voltage for item 2? Also good to check I_OUT with a current probe if possible.

Thanks,

Nick

0 murakami yusaku over 2 years ago in reply to Nick Brylski

Prodigy 10 points

Nick san

I shared some waveforms about item 2. I_OUT was measured with a multimeter sorry.

IN = ch3(blue)

OUT = ch1(yellow)

TS = ch2(green)

I_OUT = Expected value is 50mA, but unstable value of 25 ~ 27mA can be seen.

best regards.

0 Nick Brylski over 2 years ago in reply to murakami yusaku

TI__Mastermind 19195 points

thanks for attaching, we will review and get back to you next week.

nick

0 murakami yusaku over 2 years ago

Prodigy 10 points

Nick san

Are there any updates? If necessary, I'm ready to do additional validation.

best regards.

0 Jackson DiGiovanna over 2 years ago in reply to murakami yusaku

TI__Expert 8245 points

Murakami san,

Sorry for the delay. I was not yet able to find root cause for seeing 25-27mA instead of the expected 50mA. but I will check once more in the lab on Monday and get back to you then.

Thank you,

Jackson

0 Jackson DiGiovanna over 2 years ago in reply to Jackson DiGiovanna

TI__Expert 8245 points

Murakami san,

This behavior is most likely occurring because you are getting stuck in battery detect mode. This can occur around 3.8V Vbat. During this mode, the device charges at a 50% duty cycle as seen in your attached plots and checks to see when the battery voltage has increased and begins to charge normally. I am assuming here that you are using an SMU and not an actual battery here and since the SMU is forcing this voltage, it never increases and you are getting effectively "stuck" in battery detect mode. However, you should be able to recover from battery detect mode in a real application with a battery in the system rather than an SMU as the battery voltage will increase and charging will resume as expected.

Thanks and let me know if any more info is needed,

Jackson

0 murakami yusaku over 2 years ago

Prodigy 10 points

Jackson san

Thank you for your answer. I understand how it got stuck.

best regards.

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BQ25101: charge current and nCHG status at the time of Cold Fault state and recovery from it