BQ25750: Buck-boost charge solution

Tommy Tzeng

Genius 5790 points

Part Number: BQ25750
Other Parts Discussed in Thread: BQ25751, BQ25856-Q1, BQ25756,

Tool/software:

Hi Sir,

may we know about the BQ25750 can support LiFePO4 battery?

but BQ25751 does not support LiFePO4 battery, right?

so the series of BQ2575x all support MPPT function?

Does this series have spread spectrum dithering function for EMI?

thanks for your help and learn from you.

8 months ago

0 Ethan Galloway 8 months ago

TI__Mastermind 31420 points

Hello,

Thanks for being patient with this. I'm swamped with work at the moment. I'll get back to your question next week.

Best Regards,
Ethan Galloway

0 Tommy Tzeng 8 months ago in reply to Ethan Galloway

Genius 5790 points

Hi Ethan,

thanks, any update?

+1 Ethan Galloway 8 months ago in reply to Tommy Tzeng

TI__Mastermind 31420 points

Hello Tommy,

Once again, thanks for being patient with this.

Tommy Tzeng said:
may we know about the BQ25750 can support LiFePO4 battery?

Yes, the BQ25750 can support a LiFPO4 battery.

Tommy Tzeng said:
but BQ25751 does not support LiFePO4 battery, right?

Yes, this is correct.

Tommy Tzeng said:
so the series of BQ2575x all support MPPT function?

Except for the DC to DC converters, all of the BQ2575X series has the MPPT function.

Tommy Tzeng said:
Does this series have spread spectrum dithering function for EMI?

No, this series does not support the spread spectrum / dithering function.

We do have the BQ25856-Q1 that does support dithering. The BQ25856-Q1 is an automotive version of the BQ25756.

Let me know if this answers your questions.

Best Regards,
Ethan Galloway

0 Tommy Tzeng 7 months ago in reply to Ethan Galloway

Genius 5790 points

Hi Ethan,

got it, thanks for your help and reply,

may i know why is the BQ25750EVM devlopment board only design for input range of 4.2~55v? and charge voltage only 30v?

the ic can reach 70v input & output, right?

+1 Ethan Galloway 7 months ago in reply to Tommy Tzeng

TI__Mastermind 31420 points

Hello Tommy,

Yes, the IC can do operate with a 70V input or 70V output.

The BQ25750EVM board was built without the needed trace spacing to operate with at 70V. That's why we listed the EVM as only being able to do 55V. If you change the ACOV and ACUV resistors, you can operate the boards at higher voltages. Make sure to keep the boards in a safe environment when doing this.

For the output, I'll need to fix that in the EVM User's guide. The default setting is 29.4V (a 7S battery). You can change the battery charge voltage by changing R64 on the EVM.

Also, we have this BQ2575X FAQ page that may help.

Best Regards,
Ethan Galloway

0 Tommy Tzeng 7 months ago in reply to Ethan Galloway

Genius 5790 points

Hi Ethan,

thanks for your great support, may we ask some question below:

1. when BQ25750 support MPPT work, can we turn off the BATFET gate signal? throuh ACUV/ACOV ? or can i2c register support it?

2. can BQ25750 set the minmum MPPT power, and automatically open the battery power suuply(BATFET) circuit when the input power is not reached?

prevent system shutdown.

+1 Ethan Galloway 7 months ago in reply to Tommy Tzeng

TI__Mastermind 31420 points

Hello Tommy,

Your welcome. Thanks for working with us on this.

1. When the BQ25750 is charging through MPPT, the BATFETs will turn OFF automatically.

2. The BQ25750 can set the minimum voltage that can be drawn from a solar panel with ACUV. Once the voltage goes below ACUV, the BQ25750 will stop charging and turn ON the BATFETs. You may need a microcontroller to detect the minimum power that is being drawn from the solar panel.

Let me know if you have any more questions.

Best Regards,
Ethan Galloway

0 Tommy Tzeng 7 months ago in reply to Ethan Galloway

Genius 5790 points

Hi Ethan,

got it, thanks.

also, do we have Orcad file for the BQ25750 EVM ? or any CAD file can be provide?

0 Ethan Galloway 7 months ago in reply to Tommy Tzeng

TI__Mastermind 31420 points

Hello Tommy,

Your welcome. Thanks for working on this.

Here are the BQ25750 Altium Files.

Let me know if you have any questions about this.

Also, we have this FAQ on the BQ25750 power path switchover that may help as well. If VBAT is above 30V, I recommend installing an RC filter of 10Ω and 10nF on BATDRV. The 10Ω should be in series with BATDRV and the FET gate. The 10nF cap should connect from BATDRV to BATSRC.

Best Regards,
Ethan Galloway

0 Tommy Tzeng 7 months ago in reply to Ethan Galloway

Genius 5790 points

Hi Ethan,

OK~ thank for your great suggest and help.

let me confirm, you mean like the R9 and C38 in the figure below, right?

0 Ethan Galloway 7 months ago in reply to Tommy Tzeng

TI__Mastermind 31420 points

Hello Tommy,

Your welcome. Thanks for working with us.

Tommy Tzeng said:
let me confirm, you mean like the R9 and C38 in the figure below, right?

Yes, that is what I meant.

Best Regards,
Ethan Galloway

Power management

Power management forum

BQ25750: Buck-boost charge solution