BQ25895: bq25895 current limit

Raghu Tumati

Part Number: BQ25895

Hello

I have a question about the BQ25895 input current limit.

Table 7.3 give Iin = 3.25A but the max charge current is 5A. Is Iin in the table the peak current limit or the average input current?

If its peak current of 3.25A, how is a charging current of 5A possible? The charger has a buck topology and a current 5A will have to come from the input to ramp up in the inductor.

-Raghu

over 6 years ago

0 Paul Yeh over 6 years ago

TI__Genius 16145 points

Hi,

This 3.25A should be average current, not peak current.

As for why can support 5A charging current? Due to this part can support higher input voltage up to 12V, so if your input is 9V example, then your input power rating can be around 30W. And this input power should handle your charging power.

Although BQ25895 can support high power, but you still need to consider thermal design.

Thanks

0 Raghu Tumati over 6 years ago in reply to Paul Yeh

Intellectual 720 points

Hi Paul
Thank you for the quick reply. This clears all my confusion.
Two more cquestions
What is the correct way to terminate D+ and D- lines if I am not connecting the input to a USB source? Can I leave them floating?
What is the function of DSEL pin if I do not have a USB source?

0 Paul Yeh over 6 years ago in reply to Raghu Tumati

TI__Genius 16145 points

Hi,
If D+/D- are not in use, it is ok to short D+/D- to get the maximum input current limit 3.25A. If leaving both pin float, the input current limit will be set to 500mA.
As for DSEL pin, you can leave it floating if you don't need D+/D- detection.
Thanks

0 Raghu Tumati over 6 years ago in reply to Paul Yeh

Intellectual 720 points

Hi Paul

Do you mean short D+/D- to ground or just short them with each other. I would think if we short them with each other, they would still be left floating?

Raghu

0 Paul Yeh over 6 years ago in reply to Raghu Tumati

TI__Genius 16145 points

Raghu,
Please short D+/D- with each other. Just make sure they are in the same level. This connection is different from D+ and D- floating situation.
Thanks

0 Raghu Tumati over 6 years ago in reply to Paul Yeh

Intellectual 720 points

Thanks Paul

Appreciate the quick replies

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BQ25895: bq25895 current limit