CL1B power distribution

[John Watlington]

This is the current power distribution diagram for A-phase CL1B,  
identifying
what we can power, when, and how.

There are several power decisions that I believe need explaining up  
front:

- The SD slot and USB ports may be powered in suspend
     This is "just in case" some SD cards or USB devices don't handle  
being suspended
     aggressively.   We will support laptop wakeup on interrupt from any
     of these ports (SD or USB).   Under software control they may  
also be powered
     down during suspend.

- The audio codec remains partially powered in suspend
     This is in order to support "wakeup on jack insertion".  The codec
     may be placed in a very low power state during suspend.

- Power efficiency was goal number #1, therefore there are some  
voltages with
  multiple sources: one for low power (suspend) and another for high  
power (run).

Additional changes from Gen 1 include the ability to both measure DC  
input current
and VIN voltage, as well as EC control over the current drawn from  
the DC input.
The intent was to better support charging directly from solar panels.

I'm sure there are mistakes --- let me know what you think.

Cheers,
wad

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