BQ78350-DEVICE-FW: Epxlanation of Pre-Charging and Charging Voltage Low thresholds

Pietro Vignali

Hello,

we have a bq78350R2 and we cannot find in the documentation a precise explanation of the PreCharge operation.

The Advanced Charging Agoroithm has two Voltage thresholds, but it is not clear when the PRECHARGE FET is enabled and when the CHARGE FET is enabled:

- Pre-charge Start Voltage
- Charging Voltage Low

Can you please shed a light on this ?

Thanks

Pietro

10 months ago

0 Wyatt Keller 10 months ago

TI__Guru** 104835 points

Hello Pietro,

There are a couple conditions to enter pre-charge mode:

If you are outside of these conditions either both FETs will be off or CHG FET will be on.

Sincerely,

Wyatt Keller

0 Pietro Vignali 10 months ago in reply to Wyatt Keller

Intellectual 905 points

Thanks, I wasn't able to find it in the TechRef (my bad).

One further clarification: when the PRECHARGE condition is met, what condition terminate it so that normal CHARGE can start?

Thanks
Pietro

0 Wyatt Keller 10 months ago in reply to Pietro Vignali

TI__Guru** 104835 points

Hello Pietro,

Normal charge meaning the CHG FET is active instead of PCHG? If the voltage is above either of the conditions in the screenshot above it should enter normal charge mode unless something else is preventing charge.

Sincerely,

Wyatt Keller

0 Pietro Vignali 10 months ago in reply to Wyatt Keller

Intellectual 905 points

Thanks Wyatt,

so, if the gauge is already in PRECHARGE mode and charging, when it quits and start charging normally ?

Can we say that the gauge exit PRECHARGE and enters Normal Charge mode if:
1. Min cell voltage1..8 > Precharge Start Voltage

While if NOT in Charge Mode, it start normal Charge mode if:
2. Min cell voltage1..8 > Charging Voltage Low + Charging Voltage Hysteresis

(I forgot to say that our application is 8S)

Is that correct ?

Thanks, Pietro

+1 Wyatt Keller 10 months ago in reply to Pietro Vignali

TI__Guru** 104835 points

Hello Pietro,

Yes that should be the correct logic for entering normal charge.

Sincerely,

Wyatt Keller

Power management

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BQ78350-DEVICE-FW: Epxlanation of Pre-Charging and Charging Voltage Low thresholds