Pulster fixe(s) and rework
andy at openmoko.com
Thu Mar 5 10:03:40 CET 2009
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Somebody in the thread at some point said:
| On Thu, Mar 05, 2009 at 01:19:07AM +0100, Fox Mulder wrote:
|> Andy Green wrote:
|>> Johnny Tenfinger is right despite it sounds strange. On some or all A5s
|>> there is no base current limit resistor on the bipolar transistor used
|>> to light the AUX LED.
|>> This "50mA" fault current then flows not through the LED (which has a
|>> reasonable series current limit resistor), but through the GPIO IO cell
|>> and the driver transistor base.
|> If this is the problem than it really is a bad design flaw...
|> Maybe i should test the AUX LED on my gta02v5 how much current it uses
|> when it is on.
| Ouch. I just tested mine, and the AUX LED really uses that much (about
| 50mA). Does a SOP exist to fix this?
No there's no real hardware fix that's practical.
We could have done something extreme like PWM the enable by software in
FIQ ISR, but it would result in dim AUX LED even so, since the LED is
not seeing the excess current but just normally lit.
It was fixed on A6, I'm afraid we just have to let it lie and not use
the AUX LED much as pointed out unless we're on external power.
Overall, it's a small issue about small excess current on one GPIO that
spends 99.9% of its life off anyway, as a customer this would bother me
so much less than the buzz or bass issues it wouldn't really bother me
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