On Tue, 27 May 2008 10:57:18 -0700 (PDT), Tom�s � h�ilidhe
<toe@lavabit.com> wrote:
>On May 27, 6:49�pm, Tom�s � h�ilidhe <t...@lavabit.com> wrote:
>> Here's what I'm thinking of going with for the display:
>>
>> http://users.imagine.ie/toe/led_display.bmp
>
>
>Ah crap I spoke too soon. I want to be able to turn both LED's off by
>setting the uC pin to high impedence.
>
>Maybe I should add a pull-up/pull-down resistor to the microcontroller
>and then replace one of the FET's with a BJT?
Have you considered a 'high side' driver array such as the TD62783
instead of discrete components? It makes a good complement to the
2003/2803 series for array driving applications like this.
Reply by ●May 27, 20082008-05-27
On May 27, 6:49=A0pm, Tom=E1s =D3 h=C9ilidhe <t...@lavabit.com> wrote:
Ah crap I spoke too soon. I want to be able to turn both LED's off by
setting the uC pin to high impedence.
Maybe I should add a pull-up/pull-down resistor to the microcontroller
and then replace one of the FET's with a BJT?
>>>>And a 95mA max Idd and Iss, so you can't do more than 95mA absolutely.
>>
>>>Where are you getting that number from? On page 127 (PDF page 129)
>>
>
> OK, your link is dated 2004:
> http://ww1.microchip.com/downloads/en/devicedoc/41202C.pdf
>
>
>>>Abs. max Idd is 250mA
>>>Abs. max Iss is 300mA
>>>Abs. max current sunk by PORTA and C combined 200mA
>>>Abs. max current sourced by PORTA and C combined 200mA
>>
>
> My link is dated 2007:
>
>
>>Page 131 ofhttp://ww1.microchip.com/downloads/cn/DeviceDoc/cn011811.pdf
>>
>>That's strange. Are we looking at the same chip, PIC16F684?
>
> So, I won. This is progress (LOL). Probably process shrink.
Maybe, tho that is a newish device.
It could also mean they found the 95mA was all the part
was reliable to.
Not the first time a device has been 'derated' following
field feedback !
-jg
Reply by linnix●May 26, 20082008-05-26
On May 26, 11:35 am, linnix <m...@linnix.info-for.us> wrote:
> On May 24, 6:58 pm, Spehro Pefhany <speffS...@interlogDOTyou.knowwhat>
> wrote:
>
>
>
> > On Mon, 26 May 2008 10:46:14 -0700 (PDT), linnix
>
> > <m...@linnix.info-for.us> wrote:
> > >On May 24, 6:38 pm, Spehro Pefhany <speffS...@interlogDOTyou.knowwhat>
> > >wrote:
> > >> On Mon, 26 May 2008 09:26:34 -0700 (PDT), linnix
>
> > >> <m...@linnix.info-for.us> wrote:
> > >> >On May 26, 10:23 am, donald <Don...@dontdoithere.com> wrote:
> > >> >> Tom=E1s =D3 h=C9ilidhe wrote:
>
> > >> >> > Does anyone else see a problem with taking 25 mA from a
> > >> >> > microcontroller pin that's rated for 25 mA maximum?
>
> > >> >> I would look at the data sheet directly and see what is says.
>
> > >> >> Is this micro-controller a secret ?
>
> > >> >> Lets all take a look at the data sheet involved and see if this
> > >> >> micro-controller would have a problem with this.
>
> > >> >> donald
>
> > >> >I read 25mA max per pin and 90mA max per chip. Namely, no more than=
3
> > >> >leds on at any time.
>
> > >>http://ww1.microchip.com/downloads/en/devicedoc/41202C.pdf
>
> > >> I see Abs. Max 25mA/port pin and 200mA max combined port A and C,
>
> > >And a 95mA max Idd and Iss, so you can't do more than 95mA absolutely.
>
> > Where are you getting that number from? On page 127 (PDF page 129)
>
> > Abs. max Idd is 250mA
> > Abs. max Iss is 300mA
> > Abs. max current sunk by PORTA and C combined 200mA
> > Abs. max current sourced by PORTA and C combined 200mA
>
So, I won. This is progress (LOL). Probably process shrink.
Reply by linnix●May 26, 20082008-05-26
On May 24, 6:58 pm, Spehro Pefhany <speffS...@interlogDOTyou.knowwhat>
wrote:
> On Mon, 26 May 2008 10:46:14 -0700 (PDT), linnix
>
>
>
> <m...@linnix.info-for.us> wrote:
> >On May 24, 6:38 pm, Spehro Pefhany <speffS...@interlogDOTyou.knowwhat>
> >wrote:
> >> On Mon, 26 May 2008 09:26:34 -0700 (PDT), linnix
>
> >> <m...@linnix.info-for.us> wrote:
> >> >On May 26, 10:23 am, donald <Don...@dontdoithere.com> wrote:
> >> >> Tom=E1s =D3 h=C9ilidhe wrote:
>
> >> >> > Does anyone else see a problem with taking 25 mA from a
> >> >> > microcontroller pin that's rated for 25 mA maximum?
>
> >> >> I would look at the data sheet directly and see what is says.
>
> >> >> Is this micro-controller a secret ?
>
> >> >> Lets all take a look at the data sheet involved and see if this
> >> >> micro-controller would have a problem with this.
>
> >> >> donald
>
> >> >I read 25mA max per pin and 90mA max per chip. Namely, no more than 3=
> >> >leds on at any time.
>
> >>http://ww1.microchip.com/downloads/en/devicedoc/41202C.pdf
>
> >> I see Abs. Max 25mA/port pin and 200mA max combined port A and C,
>
> >And a 95mA max Idd and Iss, so you can't do more than 95mA absolutely.
>
> Where are you getting that number from? On page 127 (PDF page 129)
>
> Abs. max Idd is 250mA
> Abs. max Iss is 300mA
> Abs. max current sunk by PORTA and C combined 200mA
> Abs. max current sourced by PORTA and C combined 200mA
On May 24, 6:38=A0pm, Spehro Pefhany <speffS...@interlogDOTyou.knowwhat>
wrote:
> On Mon, 26 May 2008 09:26:34 -0700 (PDT), linnix
>
>
>
>
>
> <m...@linnix.info-for.us> wrote:
> >On May 26, 10:23 am, donald <Don...@dontdoithere.com> wrote:
> >> Tom=E1s =D3 h=C9ilidhe wrote:
>
> >> > Does anyone else see a problem with taking 25 mA from a
> >> > microcontroller pin that's rated for 25 mA maximum?
>
> >> I would look at the data sheet directly and see what is says.
>
> >> Is this micro-controller a secret ?
>
> >> Lets all take a look at the data sheet involved and see if this
> >> micro-controller would have a problem with this.
>
> >> donald
>
> >I read 25mA max per pin and 90mA max per chip. =A0Namely, no more than 3
> >leds on at any time.
>
> http://ww1.microchip.com/downloads/en/devicedoc/41202C.pdf
>
> I see Abs. Max 25mA/port pin and 200mA max combined port A and C,
And a 95mA max Idd and Iss, so you can't do more than 95mA absolutely.
>
> Does anyone else see a problem with taking 25 mA from a
> microcontroller pin that's rated for 25 mA maximum?
I would look at the data sheet directly and see what is says.
Is this micro-controller a secret ?
Lets all take a look at the data sheet involved and see if this
micro-controller would have a problem with this.
donald
Reply by linnix●May 26, 20082008-05-26
On May 26, 10:23 am, donald <Don...@dontdoithere.com> wrote:
> Tom=E1s =D3 h=C9ilidhe wrote:
>
> > Does anyone else see a problem with taking 25 mA from a
> > microcontroller pin that's rated for 25 mA maximum?
>
> I would look at the data sheet directly and see what is says.
>
> Is this micro-controller a secret ?
>
> Lets all take a look at the data sheet involved and see if this
> micro-controller would have a problem with this.
>
> donald
I read 25mA max per pin and 90mA max per chip. Namely, no more than 3
leds on at any time.
Reply by ●May 26, 20082008-05-26
On May 26, 12:11=A0am, Spehro Pefhany
<speffS...@interlogDOTyou.knowwhat> wrote:
> >I'm going to try get my hands on LED's that are bright in natural
> >daylight. Do you think I'd get much performance out of any such LED's
> >for 25 mA.
>
> Average current per LED is?
I don't know, I haven't picked the LED's yet. What I was asking about
was whether 25 mA would be enough to light any LED bright enough to be
seen in daylight (any LED on the market, that is)?
> >The rows are coming straight from the =B5C pins (the PIC16F684 pins can
> >source and sink 25 mA).
>
> "Can" as in "absolute maximum rating", which is a rather foolish thing
> to aim for in a serious design.
I don't understand your reasoning here. A spec sheet might say "Source
and sink maximum current =3D 25 mA". If I'm not mistaken, this means
that it's perfectly OK to put 25 mA thru them. If there was a need to
undercut this figure by 10%, then surely it would make more sense if
the spec sheets reduced their values by 10%.
Does anyone else see a problem with taking 25 mA from a
microcontroller pin that's rated for 25 mA maximum?