BQ25798: 9.3.6 Buck-Boost Converter Operation: SYS to MINSYS (mode 1)

THOMAS WALTER

Part Number: BQ25798

Tool/software:

Hi, I am using the BQ25798 in this schematic:

The charge is by default always enabled (CE/ tied to low).

I wanted to know if it was possible to still have SYS regulated to MINSYS as per described in 1) of: when I don't have battery nor thermistor.

Is it possible or do I have to drive HIGH CE/ ?

Best

3 months ago

0 THOMAS WALTER 3 months ago

Prodigy 150 points

By the way, when thermistor is removed (letting only RA and RB), voltage on TS is around 14% of REGN which sould trigger an overtemp event (VT5 rise set to 35,5%).

How does the chip discriminate between an overtemp and a thermistor remove ?

0 Ethan Galloway 2 months ago in reply to THOMAS WALTER

TI__Mastermind 31400 points

Hello Thomas,

Yes, it is still possible regulate SYS to MINSYS with charging disabled.

THOMAS WALTER said:
How does the chip discriminate between an overtemp and a thermistor remove ?

The chip can't tell the difference between an overtemp and a thermistor being removed. I think the charger only sets the over temperature status if charging is enabled.

Best Regards,
Ethan Galloway

0 THOMAS WALTER 2 months ago in reply to Ethan Galloway

Prodigy 150 points

Hi Ethan,

Thanks for your answer.

My question was more, as CE/ is LOW = charge enabled, is it possible regulate SYS to MINSYS with charging enabled and no battery attached ?

+1 Jing Zou 2 months ago in reply to THOMAS WALTER

TI__Mastermind 20570 points

Hi Thomas,

If charge is enabled with no battery, the charger will keeps charging the output caps to charge regulation voltage and terminate. Once the output cap discharges below the recharge threshold, charger restarts charge the output cap voltage back to the charge regulation voltage. So a short answer to your questions is no.

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BQ25798: 9.3.6 Buck-Boost Converter Operation: SYS to MINSYS (mode 1)