BQ25710: Maximum input current limit

Hi, Gil,

You can design your charger to supply more current, simply change the current sense resistor. For 10mohm, the input current is limited to 6.4A;  For 5mohm current sense, the input current could reach 12.8A. 

Disabling current limit is not suggested. 

If the system overload is temporary, you may leverage the peak power mode, such as 2ms overload every 40ms. We allow 200% overload or higher. 

ACOC is overcurrent protection. It is instantaneously protected without delay. 

More details, please see BQ25710 datasheet. 

Regards,

Tiger

Hi Tiger,

I understand "Disabling current limit is not suggested".

However, if I want to disable it, how do I do that?

Another question:

If there is no battery connected, CELL_BATPRESZ is 0V (in our design), thus the charger doesn't step-up the 12V VBUS (our DC_IN) to 16.8V (4 cells pack).
This is what I see.
My design relies on the 16.8V that always exists (even when no battery is present).

Is there a way to define the charger to produce the 16.8V (step-up works on DC_IN) when there is no battery connected?

I can tie the CELL_BATPRESZ always to 4.104-4.5V. Is that a valid solution?

thanks,

Gil

Hello Gil,

Gil Hershman71 said:

However, if I want to disable it, how do I do that?

As Tiger mentioned, disabling input current limit is not recommended. The only way to disable this input current limit is to short ACP/ACN, this is not recommend and we do not guarantee your device wil work in this state.

Gil Hershman71 said:

I can tie the CELL_BATPRESZ always to 4.104-4.5V. Is that a valid solution?

That should work, however we do not typically recommned this configuration, and we do not guarantee your device wil work in this state.

Best Regards,

Christian.

Hi Christian, Tiger,

The DC input to my system is 12V.

The charger boosts the 12V to provide a 16.8V voltage (4 cells battery). I rely on that voltage for the operation of my system (even when a battery is not connected).

I connected a 4.4V voltage to CELL_BATPRESZ. It still doesn't regulate to a 4-cell voltage (14.4V typical). I see around 12.3V.

I assume the reason is there is no I2C communication with the battery, thus "no battery".

How can I force the BQ25710 to regulate to a 4-cell battery, even when a battery is not connected?

thanks,

Gil

Hi, Gil,

This is expected. the system is regulated to min system voltage 12.3V when no battery is connected. You can raise the min system voltage through register 0x3E. 

Regards,

Tiger

Hi Tiger,

Thank you.

I understand the BQ25710, as a battery charger, acts as a SMBUS slave device only.

The smart battery can act either as a master and/or slave. By default, it will master the bus broadcast its desired charging voltage and current.

For some reason, the smart battery is not detected on the bus (address 0x0b).

Is there any register programming in the BQ25710 that might prevent it from being detected?

Is there any register in the BQ25710 that can give some information about the smart battery? (so it will show the battery is alive and communicates with the charger).

thanks

Gil 

Hi, Gil,

As a secondary device, BQ25710 should not prevent the smart battery from being detected. 

BQ25710 does not know whether a smart battery is connected or not. 

Regards,

Tiger

Hi Tiger,

So the decision to charge the battery, how "intensive" to charge it, etc., is solely based on VSYS value?

Shouldn't the SW driver of the BQ25710 decide whether to charge the battery, or not, based on parameters read from the battery and/or register definitions in the BQ25710?

I measure the BATDRV and it equals VSYS. Battery charge is not happening.

Min system voltage is configured to the maximum 0x3E = 0x3F00.

Reg 0x3F = 0x7F00.

What is missing here?

thanks,

Gil

Hi, Gil,

You can follow a few simple step in the user guide to get started. 

https://www.ti.com/lit/ug/sluubt8b/sluubt8b.pdf

Regards,

Tiger

Hi Tiger,

Good. I will implement.

When I connect an empty (discharged)  battery to the system:

I have the battery's charge current plus the load current of my system.

How does the BQ25710 balance between them?

How is the current, that flows into the system from the external DC IN, distributed between both loads (system, battery)?

thanks,

Gil

Hi, Gil,

The charger prioritizes the system load if there is a conflict.

Regards,

Tiger

Hi Tiger,

Do you mean, the system gets its required current, and if the total input current input hasn't exceeded the defined maximum, BATFET allows the battery to charge?

Can this prioritization be configured?

Another question:

When a 4-cell Li-Ion battery is being charged, is the charge "method" (or algorithm) taken care of by the BQ25710?

I mean the current charge profile.

thanks,

Gil

Hi, Gil,

Unfortunately, the prioritization could not be configured.

Yes, the BQ25710 will take care of CCCV charge profile, however, it requires the user to terminate the charge operation. 

Regards,

Tiger