Other Parts Discussed in Thread: , TS3USB221A, TLC59116, LM5175
Dear all,
I need some information that are not clear enough for me in the BQ25895 datasheet.
First let me explain what i want to achieve: I need a host-controlled battery charger, included in the system, which is able to charge from an USB source (SDP/CDP/DCP) and later HVDCP adapters, while outputting up to 3A to 3.2V blue LEDs (OTG never used). The BQ25895 seems to fit that role pretty well.
Some generic questions:
- I read that the only difference between BQ25895 and BQ25895M is the charge voltage limit (4.208/4.352V), but it seems that others registers differ too. Any other important change I'm missing?
- The MCU needs access to the USB port for communication. I consider using TS3USB221A USB switch for that purpose. A 10k pull-up resistor on DSEL is the only part needed?
And more specific information:
- Can I left STAT floating if unused?
- As I am not using OTG feature, nothing will be connected to PMID. I get the feeling that letting PMID in a floating state is not a good idea, as it seems the cap is used somehow in the buck/boost process for the SYS output. No information is given on how to choose the PMID cap value in that case, or even if that cap is needed at all.
- Is Vsys regulated at Vsysmin (3.5V) in battery-only mode (Vbus=0) while Vbat < 3.5V?
If so, it could save me a boost converter, as Vsysmin can be set to 3.7V by register.
I asked because I wonder how the BQ25895 is able to achieve, at the same time, 5V on PMID in OTG mode and 3.5V on SYS, while Vbat<3.5V, in a single Boost topology.
Best regards,
Guillaume