BQ24251 stops switching if the battery is remove and then insert

Hello, Keiichi,

Can you describe how did you remove and re-insert the battery in detail?

- What was the battery voltage before you remove it and what was the battery voltage when you re-insert?

- What was the voltage that you saw when the part start switching? Did you monitor the SW pin to tell if it is switching?

Thanks,

Wenjia

Wenjia,

Thanks for your reply.

We can duplicate battery voltage at 4.3, 4.0 and 3.6V, but it seems that it does not depends on 

original battery voltage.

I attached waveform as below

Ch1 is VBAT pin and Ch2 is VOUT voltage beyond inductor.

We once remove battery and then wait,  and re-insert at following voltages.

Case 1) NG case : Re-insert battery at VBAT=0.4V

Case 2) Good Case :  Re-insert battery at VBAT=0.8V

Case 3) Good Case : Re-insert battery at VBAT=0V

Hi, Keiichi,

I'm still trying to understand the set up here. If you don't mind, please help to provide the below information also.

- When you remove the battery, what is connected to the BAT pin of the device? I guess I'm try to know where is the 0.4V and 0.8V from.

- Do you have a power at VIN? Looks like your OUT pin stays at 2V with or without a battery, which is also not what I expected.

- For the above waveforms, did you use a real battery or a simulator to mimic the 4.3V battery?

Thanks,

Wenjia

Hi, Wenjia

There are no connection other than capatitor(10uF) on VBAT.

Also VIN have no power resources, only have 22uF+22uF+0.1uF capacitors. I guess these capacitors let VIN 2V.

We uses real battery for remove/insertion which have 4.3V, 4.0V and 3.6V (As I wrote before)

Hello, Keiichi,

I duplicated your condition on bench today, and please see the waveform attached. For a 3.6V battery, I tried insert it with VBAT = 0V, 0.4V and 0.8V just like what you did, and in all cases the system is powered on normally. If you can send me your schematic, I can try to further check the issue for you.

Also, I hope you can help me understand how the VBAT pin can have different voltages without anything connecting to it (0V, 0.4V, 0.8V). In my experiment, I used a separate power supply to mimic your condition unless the VBAT will stay 0V. The 10uF cap is a lot bigger than recommended on data sheet, can you try use a 1uF cap instead?

VBAT=0V

VBAT = 0.4V

VBAT = 0.8V

Thanks,

Wenjia

Wenjia,

At first, Thank you for duplication trials.

As for schematic, It will be customer information, so would you tell me appropriate mailing address?

I would like to send you directory.

Please send it to wenjia.liu@ti.com.

Thanks,

Wenjia

Wenjia,

 Thanks for your support.

 I sent you a schematic directory via e-mail.

I got additional information from customer.

1) They can only duplicate at 1/20 by remove/insertion batteries. Possibility is low.

2) They tried to duplicate by using DC power supply, but they can not.