TPS25751: How to enable the backup mode on the BQ25798

Richard Xu

Part Number: TPS25751
Other Parts Discussed in Thread: BQ25798, TPS552892,

Tool/software:

Hi there,
I am using a TPS25751 (has an eeprom) with a BQ25798. I have my system connected to the PMID pins and from there on it goes threw a TPS552892 where it takes it to 5V.
When I use the online web config my system powers up when usb c is plugged in but when I unplug it my PMID voltage is 0 when I unplug the usb c but the battery voltage is 4.1vs.
I am using a 1s Battery. I read in the data sheet that I need turn a register on. However, I cant seem to find how to do that in the web config. Do I need create a custom patch file?

3 months ago

0 Aya Khedr 3 months ago

TI__Mastermind 30172 points

Hi Richard,

Thank you for reaching out!

Richard Xu said:
I read in the data sheet that I need turn a register on.

Could you specify which register settings need to be enabled? When the Type-C cable is disconnected, the TPS25751 disables both OTG and charge modes.

Best Regards,

Aya Khedr

0 Richard Xu 3 months ago in reply to Aya Khedr

Prodigy 20 points

Ah, Is there a way to keep the otg mode on ? I assumed I could use the PMID as a system supply. Is there a way to enable back up mode on the BQ25798? Which is offset 16 and bit 0 on the BQ25798.
I geuss to sum up if is there a way to modify the patch file so that regisitor is enabled? Or do i have to take the binary and add it manually ?

0 Aya Khedr 3 months ago in reply to Richard Xu

TI__Mastermind 30172 points

Hi Richard,

Do you have an MCU in your system that could be connected to the TPS25751?

Could you elaborate on when back-up mode needs to be enabled? Does this need to enabled always (even during charging?)

Best Regards,

Aya Khedr

0 Richard Xu 3 months ago in reply to Aya Khedr

Prodigy 20 points

It needs to be always on.
I can have the imx8 i have on the board connect to it but I would perfer that it didnt have to.

0 Aya Khedr 3 months ago in reply to Richard Xu

TI__Mastermind 30172 points

Hi Richard,

Thank you for confirming. I need to look into this further and get back to you by the end of the week.

Best Regards,

Aya Khedr

0 Richard Xu 3 months ago in reply to Aya Khedr

Prodigy 20 points

Hi have you had a chance to see ?

0 Aya Khedr 3 months ago in reply to Richard Xu

TI__Mastermind 30172 points

Hi Richard,

The TPS25751 currently does not configure Register 16h on the BQ25798. The PD controller supports I2C pass-through where an MCU could write to the BQ through the PD controller via 4CC command (see details below).

I suggest reaching out to the Battery Charger team for proper settings to enable/disable backup mode.

Best Regards,

Aya Khedr

0 Richard Xu 3 months ago in reply to Aya Khedr

Prodigy 20 points

Is there a way to do that or is that not possible ?

0 Aya Khedr 2 months ago in reply to Richard Xu

TI__Mastermind 30172 points

Hi Richard,

Unfortunately, this would not be possible with our current implementation. We will look into adding this feature into our next GUI release.

Best Regards,

Aya Khedr

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TPS25751: How to enable the backup mode on the BQ25798