Power Management on Neo1973

Shawn Rutledge shawn.t.rutledge at gmail.com
Sat Jan 12 06:47:50 CET 2008

On Jan 10, 2008 2:57 PM, Shawn Rutledge <shawn.t.rutledge at gmail.com> wrote:
> Yeah.  I wonder if the battery has deteriorated somehow (from the
> phone running and being plugged in to USB for days or weeks at a time,
> and being overcharged? but the power management chip should not
> overcharge it, right?), or maybe it is not being fully charged.  I
> consider it fully charged when it has been running, and plugged in to
> USB, overnight.  I'm also wondering if my hub may be limiting it to
> less than 500 mA though.  I need to measure the currents... both
> battery current and USB current, in various states.

Well I made a sort of "current probe" by gluing two pieces of very
thin single-sided PCB material back-to-back (the result is thinner
than any double-sided stuff I have at home).  I see -375mA (current
coming out of the battery) as the usual load.  But when USB is plugged
in, I see between -60 and -80 mA - current is still coming out of the
battery.  So it's not getting charged; my hub must be limiting the
current.  Let me plug in directly to my PC... OK now it's +25-+45mA,
still fluctuating all over but charging the battery slowly.  I checked
and it is in fast_cccv mode.  So I guess that means the USB current is
probably 400mA or less... we have a load of 375mA plus some charge
current is going into the battery, but the charge happens at a
different voltage, but there is some loss in the charge circuit too.
Now I unplug USB for a second and it goes to 450mA load current
(coming out of the battery to run the phone).  OK 375 was lower than
normal for some reason...

So far that was running gllin, and logging data points, with the LCD
and backlight on and showing the splash screen, but not running the
UI.  Not sure if GSM is on in that state or not.  OK I will try it
with a SIM installed, and running the UI...

BTW current discharge is about 8-12 mA with the phone turned off.
It's dropping a little over time.

While the UI starts up the battery is still discharging.  Now that
it's sitting at the main screen the current is about +35-+40mA,
charging the battery.  Well it's not receiving a call.

fluctuates a lot too, from 693-2026 as I checked several times.  Tried
unplugging USB again to see the load current (coming out of the
battery when it's not charging); that is still 450mA.  But when I plug
it back in, USB is misbehaving:

usb 2-1.1: khubd timed out on ep0in len=0/64
usb 2-1.1: khubd timed out on ep0in len=0/64
usb 2-1.1: device descriptor read/64, error -110
usb 2-1.1: khubd timed out on ep0in len=0/64

and the battery current is -350mA (because it's taking 100mA from USB
by default, right).

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