Thanks for the diagram!
But I have one more question. Is it really necessarily to operate bq24193's I²C bus at 1.8V?
According to datasheet http://www.ti.com/lit/ds/symlink/bq24193.pdf
The 1.8V was used only as example of operating voltage..
The Absolute Maximum Ratings for all SDA, SCL and INT pins is 7V and both are "i2c standard open collectors" and could be pulled-up to any rail within the operating voltage range..
Therefore I think the Voltage translator is not necessary...

Kaklik

2016-03-02 19:20 GMT+01:00 Luke Kenneth Casson Leighton <lkcl@lkcl.net>:
---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Wed, Mar 2, 2016 at 4:48 PM, Luke Kenneth Casson Leighton
<lkcl@lkcl.net> wrote:
> On Wed, Mar 2, 2016 at 4:25 PM, Jakub Kákona <kaklik@mlab.cz> wrote:

>>  But a
>> current design is still not fully clear to me.

 ok i've created a diagram, it's basically identical to the current
PCB3 schematic, except LTC4155 is replaced by a combination of bq24193
plus txs0104 plus 1.8v regulator, and STC3115 is replace by BQ34Z100.

 http://hands.com/~lkcl/eoma/laptop_15in/pcb3_diagram.png

 key differences from what you *might* be expecting this Charger PCB to have:

 1) there is NO 5V rail.
 2) there is NO 12V rail
 3 ) there is NO 3.3v rail
 4) the (appx) 4.2V "SYS" voltage from the Charger IC goes straight out *as-is*
 5) Digital GPIO requires a REF voltage to be safe and meaningful.
     this *has* to be EXTERNALLY SUPPLIED.
 6) many devices are now USB-OTG compliant (2-way power),
    so that is a power output (***AND POWER INPUT***)

 from what you wrote, you *may* have considered that something like
this would be useful:

 1) 5V DC output
 2) 12V DC output
 3) 3.3v output
 4) DC charging input

such a board is not useful for this project, because such a design is
for a standard laptop.  this isn't a standard laptop, it's a
USB-OTG-powered "embedded" device.

l.

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