Better characterization of suspend current

Andy Green andy at
Tue Feb 12 13:48:43 CET 2008

Hash: SHA1

Somebody in the thread at some point said:

> Just to give you something to think about, I'll describe the power

It's good, I don't have enough to think about :-)  Just kidding this was
very interesting.

> In suspend the only thing that's still powered is the 32MB ram chip
> (there's no modem).  It turns out this is so well done that on several
> occasions it has been sitting in my drawer for over 6 months and later
> when charged, resumed with the button press into the same state it was
> left in a fraction of a second.  This is cool because it makes the

This is where we want to get to alright, but I'm not sure we can get
there with just software from here.  There's no way if we can only push
suspend current to 4mA we will last a couple of weeks let alone six
months.  Suspend current of 400uA we can start to think in those terms.

To put this into perspective, the SDRAM in the S3C2242 datasheet claims
a 220uA selfrefresh current.  So where is the rest of our 4 - 5mA
getting blown?  WLAN or something like that?  Can it still be some small
mistake we made on Glamo GPIO or something?

One way or another a more violent inspection of where that current is
going is in our future and then yes the behaviour you laid out will be

- -Andy
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