Reply by Ben Bradley May 28, 20082008-05-28
On Tue, 27 May 2008 10:57:18 -0700 (PDT), Tom�s � h�ilidhe
<toe@lavabit.com> wrote:

>On May 27, 6:49&#4294967295;pm, Tom&#4294967295;s &#4294967295; h&#4294967295;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:
> 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?
Reply by May 27, 20082008-05-27
Here's what I'm thinking of going with for the display:

http://users.imagine.ie/toe/led_display.bmp
Reply by Jim Granville May 27, 20082008-05-27
linnix wrote:
<snip
>>>>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) >
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.
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
Page 131 of http://ww1.microchip.com/downloads/cn/DeviceDoc/cn011811.pdf That's strange. Are we looking at the same chip, PIC16F684?
Reply by linnix May 26, 20082008-05-26
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.
Reply by donald May 26, 20082008-05-26
Tom&#4294967295;s &#4294967295; h&#4294967295;ilidhe 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
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?