BQ25883: recommended IBAT current

Kazuto Tatsumi

Intellectual 2820 points

Part Number: BQ25883
Other Parts Discussed in Thread: BQ25890, BQ25792

Hi team,

BQ25883 accepts IBAT<9A up to 1us per datasheet, but it is 1s at BQ25890. Is it really "1us" at BQ25883?

Regards,
Kazuto

over 4 years ago

0 Wyatt Keller over 4 years ago

TI__Guru** 105770 points

Hello Katuto,

Let me double check, some of the protection thresholds nay be different between the chargers.

Sincerely,

Wyatt Keller

0 Kazuto Tatsumi over 4 years ago in reply to Wyatt Keller

TI__Intellectual 2820 points

Hi Wyatt,

If it's just a recommendation and no problem to exceed for "few milliseconds", maybe we should suggest the customer to ensure good thermal design on their PCB then it will be fine. what do you think?

Regards,
Kazuto

0 Wyatt Keller over 4 years ago in reply to Kazuto Tatsumi

TI__Guru** 105770 points

Hello Kazuto,

I believe that the information on the datasheet is correct due to the internal structure differences between the chargers. The max current is related to the internal structure. I'll let you know when I get more information.

Sincerely,

Wyatt Keller

0 Kazuto Tatsumi over 4 years ago in reply to Wyatt Keller

TI__Intellectual 2820 points

Hi Wyatt,

Thank you for your support. Please let me know once you get more information.

Is it possible to connect SYS and BAT directly? what problem expected?

By the way if the customer considers an alternative, how about BQ25792? Do you have any recommendation to handle over 9A peak SYS current?

Regards,
Kazuto

+1 Wyatt Keller over 4 years ago in reply to Kazuto Tatsumi

TI__Guru** 105770 points

Hello Kazuto,

I confirmed that it is due to the internal differences that the 1us limit is correct.

If you connect VSYS to VBAT during charge the BQ25883 will not be able to measure the current flow, so it would not be able to regulate it. If you want to bypass the BATFET to increase the discharge current you will need to add an external FET in parallel that is only active during charge.

I'm not as familiar with the BQ25792 charger, but the IBAT_OCP is also around 9A (9.3A min) so I'm not sure if that charger is a much better option.

Sincerely,

Wyatt Keller

0 Kazuto Tatsumi over 4 years ago in reply to Wyatt Keller

TI__Intellectual 2820 points

Hi Wyatt,

Understood. Thank you for your confirmation. By the way do we have some app note or reference design to realize external FET? do you mean an external FET is active during "discharge"?

Regards,
Kazuto

+1 Juan Ospina over 4 years ago in reply to Kazuto Tatsumi

TI__Mastermind 18015 points

Hi Kazuto,

If I understand correctly, you are expecting an increased current during a load transient.

If you know in advance when the load transient will occur, you can externally enable the FET for the duration of the transient, but only when you are certain that there is no possibility for charge current to flow into the battery from SYS. If discharge current is within specifications after the transient passes then the FET can be disabled and discharge can continue through the IC.

I don't believe we have any app notes or reference designs for this particular case. Some considerations to have when designing this FET circuit is the current expected and for which the FET is rated. Additionally take into account any possibilities for current flow through the FET while it is disabled, this should be eliminated if possible.

Best Regards,

Juan Ospina

0 Kazuto Tatsumi over 3 years ago in reply to Juan Ospina

TI__Intellectual 2820 points

Hi Juan,

Thank you for the description, I could understand what did "external FET' mean.

Regards,
Kazuto

0 Juan Ospina over 3 years ago in reply to Kazuto Tatsumi

TI__Mastermind 18015 points

Hi Kazuto,

By external FET, we mean the addition of a FET/MOSFET that is separate from the charger IC. This FET could be placed to enable current flow between SYS and BAT when enabled. It would have to be controlled by your host microcontroller and enabled only when you expect the load transient to exceed the rated discharge current.

Best Regards,

Juan Ospina

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BQ25883: recommended IBAT current