BQ25619E: Vsys ringing when VBUS connect/disconnect event

Jiri Otisk

Part Number: BQ25619E
Other Parts Discussed in Thread: BQ24259,

Hello, I have problem with bq25619E I used is as more available replacement of bq24259 which works great with same board and topology. When VBUS is connected or disconnected I have MCU reset on brown out. BQ registers as per screen. VSYS in on scope enclosed during disconnection of VBUS. PCB layout and schematic enclosed. Any ideas what is wrong will be welcome.

Thank you, Jiri.

over 4 years ago

0 Wyatt Keller over 4 years ago

TI__Guru** 106455 points

Hello Jiri,

Is the waveform shared of VSYS while VBUS is disconnected? It's pulsing every disconnection or while VBUS is disconnected?

Can you share a scope capture with VBUS, VSYS, and VBAT so we can get a better idea of the test?

I would also recommend adding some lower capacitance caps to filter out some of the high frequency noise.

Sincerely,

Wyatt Keller

0 Jiri Otisk over 4 years ago in reply to Wyatt Keller

Intellectual 280 points

Hello Wyatt,

please see waveforms below. traces have offset to make it clearer. Yellow VBUS (offset 0), blue VSYS (offset -1V), purple VBAT (offset +1V).

All connection events are with discharged caps. AC adaptor, cables and PC host are same as for bq24259 tests which passed without problems. AC adaptor is 5V/1.2A Sunny SYS1421-0605-W2E.

AC adapter connection:

zoom area 1

zoom area 2

zoom area 3

zoom area 4

PC usb connection:

zoom at rising edge:

Thank you.

0 Jiri Otisk over 4 years ago in reply to Wyatt Keller

Intellectual 280 points

Following waveforms are when connected and charging.

AC:

PC USB:

0 Jiri Otisk over 4 years ago in reply to Wyatt Keller

Intellectual 280 points

Original waveform is possible to replicate only without battery connected, as below during USB insert event:

zoom out, after VBUS rised up typical caps pumping is observer, that is OK.

100nF and 1nF connected in parallel to VBUS and VSYS, AC connected.

zoom 1

zoom 2

zoom 3 , this should be most important event which cause MCU reset/brown out.

0 Wyatt Keller over 4 years ago in reply to Jiri Otisk

TI__Guru** 106455 points

Hello Jiri,

Thanks for the additional information, since it only occurs when the battery is not connected I believe you need to disable the charge to stop that behavior. You can find the explanation on this thread: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/875388/faq-bq24190-bq2419x-bq2429x-faqs

It is the #1 on the FAQ.

Sincerely,

Wyatt Keller

0 Jiri Otisk over 4 years ago in reply to Wyatt Keller

Intellectual 280 points

Unfortunately only /resized-image/__size/320x240/__key/communityserver-discussions-components-files/196/SCN15-no-batt.PNG

and

/resized-image/__size/320x240/__key/communityserver-discussions-components-files/196/SCN17-no-batt2.PNG

are without battery and was added to make measurement complete.

All other measurements are with connected battery. restart event occur with battery. Battery is charged to approx 4V when test was done.

0 Wyatt Keller over 4 years ago in reply to Jiri Otisk

TI__Guru** 106455 points

Hello Jiri,

If you increase the capacitance on your VBUS and VBAT close to the IC does the issue still remain? Are you sure this isn't from the AC adaptor being used causing noise to propagate?

The screenshots sent without the battery is definitely due to the recharge voltage threshold as the capacitance on the BAT pin is charged/discharged.

Sincerely,

Wyatt Keller

0 Jiri Otisk over 4 years ago in reply to Wyatt Keller

Intellectual 280 points

Hello Wyatt,

thank you for tip, I was amazed about AC noise to be honest, this power supply is very smooth in normal conditions. I will make more tests with filtering on input after 14 days as I'm on holidays at moment. Will keep you updated.

0 Wyatt Keller over 4 years ago in reply to Jiri Otisk

TI__Guru** 106455 points

Hello Jiri,

No problem, just let us know if you have more questions.

Sincerely,

Wyatt Keller

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BQ25619E: Vsys ringing when VBUS connect/disconnect event