Tool/software:
Following up with design presented here. I have a 6 cell Li-ion package. My target charging voltage is set to 24.66V (with VFB pin), fast charge current set to 1.06A (with ISET1) and termination current to 0.15A (with ISET2).
My design can now correctly control charging current, and state signalling also works fine. However there are still two concerns:
1. During charging with full current (datasheet calls it "Fastcharge current regulation phase"), i.e. 1.06A (verified value). BQ14610 chip heats up from room temp up to 65deg Celcius, after about 10 min of charging. As the device itself does not perform any high current switching, I am suprised that it generates so much heat. It is placed on thermal pad that is connected with vias down to layers below. Is this heat generation something expected, or may it be a symptom of some other problem?
2. During end stage of charging ("Fastcharge voltage regulation phase"), when current is ramped down, the output voltage (called "Vpwr" on my desing, or "SYSTEM" in datasheet), experience little bumps from 25.9V to 28V. These bumps last about 0.5ms, and are repeated every 5-6ms. These cause audible effect on input ceramic capacitors (C1102 on my design, C8, C9 on datasheet fig. 20). What is significant, is that these bumps reach voltage that is higher than input power adapter, and obviously that battery voltage. It means this voltage must have been induced by switching action of charger. I can deal with the noise somehow, but again - is it something that can happen with BQ charger, or should I be worried that it is a symptom of underlying design error.
I'd be very grateful for any insight or idea or tip regarding these 2 problems.
Below you'll find a fragment of schematics and PCB area of charger.
Cheers!
Mateusz
