[Arm-netbook] EOMA68 laptop battery management.

Jakub Kákona kaklik at mlab.cz
Wed Mar 2 22:49:23 GMT 2016

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...


2016-03-02 19:20 GMT+01:00 Luke Kenneth Casson Leighton <lkcl at 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 at lkcl.net> wrote:
> > On Wed, Mar 2, 2016 at 4:25 PM, Jakub Kákona <kaklik at 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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