BQ25895: disruptive peaks

Tomas Kopecny

Prodigy 20 points

Part Number: BQ25895

Tool/software:

Hello,

please I need help with this problem:

I have BQ25895 set in OTG mode and I use boost.

I am not using VBUS yet, so there is no voltage on VBUS.

I use the default registry settings.

Electronics schematics are as follows see attachment schema page-19.

https://www.ti.com/lit/ug/sluuba2b/sluuba2b.pdf?ts=1743053480177

PMID without load

BQ25895 has large voltage drops even without load see attachment PMID-osciloscop (free_load).

these peaks reach up to 1.5V.

How can I remove the problem spikes ?

PMID with 360mA - looks okay

PMID-osciloscop (360mA_load).

3. PMID more than 400mA - chip OFF

If I connect a load (more than 400 mA), the chip detects the drop and turns off.

Due to peaks see point 1 there will be a voltage drop and BQ25895 detects a shutdown.

How can I remove the problem ?

- I have met all the PCB layout conditions page-11.

https://www.ti.com/lit/ug/sluuba2b/sluuba2b.pdf?ts=1743140913462&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FBQ25895EVM-664

- I have the components that are recommended.

- I tried to find my problem on ti.com forum but I didn't find the answer.

- I have the battery connected by soldering so that there is as little resistance as possible.

Please advise what could be the cause of the problem point-1 ?

Thank you and have a nice day

Tomas

3 months ago

0 Alec Lehman 3 months ago

TI__Expert 6850 points

Hi Tomas,

Thanks for reaching out.

It looks like the attachments did not send. Could you please resend them so I can review the waveforms?

Best regards,

Alec

0 Tomas Kopecny 2 months ago in reply to Alec Lehman

Prodigy 20 points

Hi Alec,
I really can't send attachments, I don't know what to do with it. Because the form and insert only allows me to send the URL of the image, but I don't have it shared anywhere.

So how do I send images from the oscilloscope?

The only thing I can send is a print screen form, that works

Thanks and have a nice day.
TK

0 Alec Lehman 2 months ago in reply to Tomas Kopecny

TI__Expert 6850 points

Hi Tomas,

Thanks for reaching out.

Try copying and pasting the image into the field. Alternatively, there should be an option to upload the file directly:

Best regards,

Alec

0 Tomas Kopecny 2 months ago in reply to Alec Lehman

Prodigy 20 points

360mA load

--------------------------------------------------------------------

Free load 1

Free load 2

Free load 3

0 Juan Ospina 2 months ago in reply to Tomas Kopecny

TI__Genius 16955 points

Hi Tomas,

Significant voltage drops are not expected in low load conditions.

Can you please share waveforms of VBAT, VSYS, SW, and PMID in parallel to see if the boost output is being impacted along the power source path? Additionally, can you please share the register values when un-loaded, when 360mA load, and after the 400mA load collapse?

Best Regards,

Juan Ospina

Power management

Power management forum

BQ25895: disruptive peaks