BQ25792: schematic check request

Tommy Tzeng

Genius 5780 points

Part Number: BQ25792
Other Parts Discussed in Thread: BQ25798

Tool/software:

Hi Team,

could you help check if there any problem with this schematic? after our review, there seemed to be no issue.

BQ25792RQMR_Schematic Review.pdf

over 1 year ago

0 Jibin Biju over 1 year ago

TI__Intellectual 995 points

HI Tommy,

I don't see any obvious issues. The only thing is that ILIM isn't set to 3A as it is stated in the schematic (it assumes REGN is ~4.3V which it isn't). Also, if I may ask what is the purpose of R453, R454, C457, and C458?

Best Regards,

Jibin

0 Hung HanTse over 1 year ago in reply to Jibin Biju

Prodigy 150 points

Hi Jibin,

1. About the ILIM is 3A, my calculated is as blow.

VREGN=4.8V, The VILIM= 4.8V*100K/(100K+43.2K)=3.4V ILIM=(3.4V-1V)/0.8=3A

2. The schematic modification is as attachment about I remove the R453, R454, C457, and C458.

Plesae help me review about second review, thanks.

3. I want to ask for your experience about the negative voltage when the battery connector(J6) plug in, this issue happen on other project and not TI product.
I'm not sure that I add the protect circuit helpful or not on battery connector.

BQ25792QMR_Schematic Review 2.pdf

0 Jibin Biju over 1 year ago in reply to Hung HanTse

TI__Intellectual 995 points

Hi Hung,

I apologize for the miscalculation. BAT and BATP can't handle more -0.7V. External protection would be needed. If you are hot plugging the battery, we recommend you place 200uF at BAT/BATP pin. We recommend using BQ25798 for this application.

Best Regards,

Jibin

0 Jeff F over 1 year ago in reply to Jibin Biju

TI__Guru**** 166626 points

Hi Hung,

To clarify, the 200uF is only needed for 792 if the user will be hot plugging the battery and TS function is disabled. Otherwise, the charger will hit OVP and turn off the converter for 30ms at battery removal, which can cause SYS voltage to collapse. BQ25798 is pin 2 pin and reg 2 reg compatible, still has the OVP event at battery removal but does not turn off the converter for 30ms.

Regards,

Jeff

0 Hung HanTse over 1 year ago in reply to Jeff F

Prodigy 150 points

Hi Jlbin and Jeff,

Thanks for your remind. We reference other project design about battery connector protect circuit.

I would like to ask if such a design can meet the negative voltage that may be generated when the battery is plugged in and out, or is there a recommended protection circuit that I can refer to?

0 Jibin Biju over 1 year ago in reply to Hung HanTse

TI__Intellectual 995 points

Hi Hung,

For negative spikes a Schottky diode is likely good enough. We would recommend a 47nF at BATP since you have a shipFET and you are hot plugging 3S battery. Please follow Jeff's suggestion for BATOVP to prevent the converter from shutting down.

Best Regards,

Jibin

0 Hung HanTse over 1 year ago in reply to Jibin Biju

Prodigy 150 points

Hi Jlbin,

I already modify 33nF to 47nF at BATP, thanks for your advice.

0 Tommy Tzeng over 1 year ago in reply to Jibin Biju

Genius 5780 points

Hi Jibin,

thanks for your support,

as attached, could help double confirm the layout and any suggestion? thanks.

password:20240806

BQ25792QMR_Schematic Review_Final(1).pdf

6000087ZBATE-0806-JOB.zip

0 Jibin Biju over 1 year ago in reply to Tommy Tzeng

TI__Intellectual 995 points

Hi Tommy,

There is comment on the schematic says you want 10A at SYS, not sure if that is possible, and other that I don't see any obvious issues. The Layout will be checked by the end of tomorrow.

Best regards,

Jibin

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BQ25792: schematic check request