power consumption after shutdown

Richard A. Smith richard at laptop.org
Sat Feb 14 18:05:27 EST 2009

Richard A. Smith wrote:

> into STOP mode but its power draw suggests otherwise.  I'll have to 
> study it deeper.

After deeper study I have verified that the EC is going into stop mode. 
  I have also found the (biggest) source of the additional power draw I 

The tinder box XO has the EC serial port connector loaded and has a 
TTL->USB adapter connected.  The 3.3V EC rail is ORed in with the 3.3V 
regulator from the 5V USB since the device can be powered by either 
side.  Disconnecting the EC serial port drops the power draw to 1.6mA. 
This also tells me that the reading listed as EC is not just the EC but 
all the devices connected to that rail.

The instrumented setup only has a current measurement resolution down to 
about 1mA.  So there's room for a lot of error in that measurement. 
Looking at the schematics I see that there are quite a few other parts 
that share the 3.3V rail with the EC so 1mA or so seems reasonable.

I've started a long term measurement test using the ACR guage inside the 
battery.  I'll check it on Monday.

Richard Smith  <richard at laptop.org>
One Laptop Per Child

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