BQ25120: Integrated buck default output voltage set to 1.1V

Hello Damien,
Sorry so hear you're having issues. A similar issue was found here: e2e.ti.com/.../2291419 . This might help to solve this. Is the CD Pin high or low when this occurs?
Regards,
Raheem

Hello Raheem,
Thanks for helping us. We found this post as well, but since the is no I2C communication at all we don't think this is the same issue. To make sure of that we removed the I2C_SCL pull-up before powering up the board so that I2C bus is not working, still got 1.1V on the output.
The CD pin is low.
Thanks,
Damien

Damien,
By default, the SYS voltage should be 1.8V. Try to disconnected any communication between your microcontroller and the IC. Then turn both your battery and VIN off then on and check to see if the output voltage is still 1.1V. Leave everything connected to SYS as is.
Regards,
Raheem

Raheem,
As mentionned before we disabled the I2C bus by removing the SCL pull-up resistor to make sure there was no communication. Anyway we monitored both SCL and SDA with an oscilloscope today while recycling the power as you explained, there is no I2C communication and still 1.1V.
Thank you,
Regards,
Damien

Damien,

Please set the board back to the default settings as shown below and let me know what the SYS voltage is. Also, are both VIN and BAT present when this issue occurs? If only BAT is present, CD should be pulled High.

Regards,

Raheem

Hi Raheem,

I clicked on the resolved issue by mistake, this has not resolved the issue.
Pulling CD pin high does not help.
To answer your question, only VBAT is in, but the same configuration on the EVM board (with CD pulled low internally at 900k) works fine (i.e. we have 1V8 on the EVM output).

I can't find where to mark this issue as not resolved, I'll keep looking but if you could help switch it back to "not resolved" it would be appreciated.
Thanks,

Damien

Damien,
Try clicking on more and check to see if you can undo 'resolved'. Did you try setting the values back to default and checking the SYS voltage?
Regards,
Raheem

Raheem,
Can't find where to undo "resolved", could you please check on the admin side if someone can do that?
About the default values, we can't power our MCU so no default setting has been modified. Aren't all registers reset back to default when the IC power is recycled anyway if that was the case? The only things that are different from the list you provided are the ISET, PRETERM and ILIM resistors not being set exactly as described, but I can't believe that would be the reason it fails to deliver 1V8 by default, otherwise everyone would be having issues.
Regards,
Damien

Damien,

Can you post scope captures of the powerup? With VIN plug and I would like to see PMID, VSYS and VBAT. 

Can you also confirm that the I2C lines are pulled up to VSYS? 

Regards,

Gautham. 

Hello Gautham,

I2C lines are indeed pulled-up to VSYS.

We only have an old 2 inputs oscilloscope without screenshot abilities so please excuse the bad quality of the pictures below.

What I understood is that you wanted to see plots of PMID, VSYS and VBAT with a trigger on VIN ramp-up. If that wasn't the case please tell me so that I can upload what you need.

Please not that Vin ramp-up is not smooth because it is generated from wireless charging, however the issue also being present without VIN plugged in shows this is not the problem here.

Regards,

Damien

Damien,

Thanks for the plots. this is good information to check. There is nothing supicious which is a good thing. 

Now would you be able to read out all the I2C registers? (especially when this issue is seen?)

regards,

Gautham

 

Gautham,

Here is the registers dump result when the issue is seen:

Register	Value
0x00h	0x03
0x01h	0x40
0x02h	0x88
0x03h	0x00
0x04h	0x02
0x05h	0x00
0x06h	0x80
0x07h	0x00
0x08h	0x00
0x09h	0x00
0x0Ah	0x7C
0x0Bh	0x00

Thanks,

Damien

Excellent! Issue found! 

You have register 0x06 (SYS_VOUT) as data 0x80. This corresponds to a 1.1V setting. 

You would need to have it as data 0xAA. Are you writing this register accidentally on powerup?

Regards,

Gautham

Actually, as described in the first post, we already saw that 06h register value is not what it is supposed to be, but we do not write anything on it. Please check the very first post for details.
Thanks,
Damien

Hi Gautham,
Any update on what could possibly cause this issue? We 're still stuck on this.
Thanks for your support,
Regards,
Damien

Damien,

How many boards are exhibiting this issue out of how many? Where did you obtain these parts from?

It is almost impossible to have the OTP bits flipped. 

regards,

Gautham

Gautham,

12 out of 12 boards have this issue. However we did another FPC batch with another factory and we do not have this issue (the design is strictly identical, but components ordering was not made at the same time).

For those 12 boards that have the issue, BQ25120 where bought by our Chinese team to a local broken called Onenew.
Regards,
Damien

Damien,

This answers my suspicion. I am not sure how the disti even got parts without a waiver for an unreleased device. We have many versions of this part and they have been able to secure some- most probably that were given as free samples (under a waiver).

They should contact TI through the channel they purchased.

Regards,
gautham

Hi Gautham,
So to be clear, what you are saying is that we indeed have parts with 1.1V default output voltage, and that all we can do is replace them?
Thanks,
Damien

Hi Gautham,

Thanks for your reply, that's a shame though.
We will send the boards for rework with new parts and see if we can get that 1.8V output right.
I'll post an update here later.
Thanks,

Damien