BQ24075T: Capable of supporting lower charge currents with same accuracy as bq2407x (non-T)?

Jonathan Bender

Part Number: BQ24075T
Other Parts Discussed in Thread: BQ24075,

Hello,

I have an application where I might want to use the bq24075T to charge a battery at 190 mA. I noticed that the bq24075T datasheet has a specified minimum of 300 mA (R_ISET = 3 kohm), whereas the bq24075 is specified down to 100 mA (R_ISET = 8.9 kohm).

Can you verify that the accuracy of bq24075T is only suitable for R_ISET >= 3 kohm Or can the bq24075T support the same fast charge range and accuracy as bq24075?

The two devices seem very similar, so I was wondering if perhaps the bq2407xT datasheet was never updated, as the new, lower range for non-T came in a 2014 revision.

Thanks,

Jonathan

over 6 years ago

0 Bill Johns over 6 years ago

TI__Guru 68146 points

Hi Jonathan
The Data Sheet has changed the Min Fast Charge current range, resistor setting and applications section. This would indicate it is not an oversight.
I suspect this is driven by termination current accuracy is driving the requirement. This is 3.3% for USB100 mode (100mA) and 10% for other conditions.

Will this application used USB100 mode?

0 Jonathan Bender over 6 years ago in reply to Bill Johns

TI__Expert 7895 points

Hi Bill,

The device will be configured to start in USB500 mode when the charge current is set to 192 mA (R_ISET = 4.64 kohm). So it would be in the 10% termination accuracy region, which is fine for this application. But since the max R_ISET in the "recommended operating conditions" for bq24075T is 3 kohm, it doesn't seem like the 4.64 kohm would be covered by the I_TERM accuracy specs.

I also noticed that later on in the bq24075 datasheet, it suggests 5.9 kohm as the max R_ISET, not 8.9 kohm. Even that maximum would be fine for us with bq24075T, but it seems odd to me that these two devices would have a different spec here when they otherwise seem very similar.

bq24075: