GPIO0 trough 2 shorted to ground

Andy Green andy at
Sat Feb 23 06:30:16 CET 2008

Hash: SHA1

Somebody in the thread at some point said:
> Andy Green wrote:
>> What's notable is we might as well save current by throwing out the NPNs
>> and drive the LEDs directly then :-)
> And the GPIO pins would suffer 75% less ;-)

Well the pins love it, it's the transistor driving them and specifically
selfheating.  But I don't think it makes serious trouble since currently
PWM is broken on resume and all the LEDs are 100% lit then, it stays
that way for hours without making trouble known: and that is very much
not the normal situation for this phone for battery reasons.

However we should do something about it as soon as practical, which may
be series resistors or your built-in idea for A6... of course if sooner,

>> A fix we might be able to do is change the NPNs into N-Channel MOSFET in
>> same package.
> If we can source such parts on short notice, which is often much
> harder than you'd expect. (I'll have to tell you about the sourcing
> adventures of our glorious past over a beer :)
> Otherwise, we may use transistors with built-in resistors, of which
> we already have a few in our designs. That would also spare us the
> re-layout.

There is a dual NPN in one package on the dual LED, I guess it makes
either way a bit  harder to find equivalents.

- -Andy
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