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'[PIC] 5V PIC24?'
2006\09\20@221341 by Bob J.

picon face
I've been considering going with a PIC24H on my next project (need many
analog inputs...the PIC24HJ128GP510  has 32 12-bit
ADC's)<www.microchipdirect.com/ProductSearch.aspx?Keywords=PIC24HJ128GP510>,
and as I was trying to find some parts to sample I found that the PIC24's
aren't available as 5V parts.  What's up with that?  That is going to be a
problem with some of the devices I plan on using with the PIC24, notably
some 5V SPI devices and an LCD.

Why would Microchip not produce 5V versions of these devices?  In
applications where low power consumption is not a requirement I can't see
why one would want to migrate their designs to 3V unless I'm missing
something.

Regards,
Bob

2006\09\20@225312 by Marcel Duchamp

picon face
Bob J. wrote:
> Why would Microchip not produce 5V versions of these devices?  In
> applications where low power consumption is not a requirement I can't see
> why one would want to migrate their designs to 3V unless I'm missing
> something.

Say this slow and deliberately:
"Mr. Anderson;  that is the sound of inevitability"
(from The Matrix I)

What do chip fabs want? Better yield.
What (in general) gives better yield? Smaller feature sizes.
What do (in general) smaller geometries have in common? Lower voltages.
Do you see a trend here?  I thought so.

It's unfortunately as inevitable as the move to impossible-to-solder
packages.

I'm with you Bob, let's stop progress now and keep it easy!  The current
bane of my life?  BGA parts.  We pay for xray examination and they still
have problems.

I guess it's called "modern life"... the more it changes, the faster it
changes.


2006\09\21@010832 by Jesse Lackey

flavicon
face
If you just need to send data to 5V devices, the 3.3V output is often
good enough.  Check the specs on the devices.  I've run 5V LCDs no problem.

If you have 5V inputs, either see if any PICs have "5V tolerant" i/o (no
idea if microchip does this, other manufacturers sometimes do) and if
not you can use a level translator, such as a 74LVTH125 for those inputs.

A real dirty trick is to have the 5V input go thru a resistor, say 1K,
then to the PIC input pin, and have a diode from the pin to 3.3V.  The
1K current-limits and the diode keeps the voltage on the PIC pin to 3.3V
+ Vf.  An even dirtier trick is to not bother with the diode, and just
let the PICs internal input protect diodes conduct to the internal
+3.3V.  I wouldn't do this for a production design.  It may affect A/D
accuracy and may lead to early device failure.  It also won't work for
fast-moving signals (they will have real slow rise/fall times), because
the 1K forms an RC filter with parasitic capacitance on the PIC input pin.

But it will probably work just fine for decades.

J


Bob J. wrote:

{Quote hidden}

2006\09\21@014906 by Herbert Graf

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face
On Wed, 2006-09-20 at 22:13 -0400, Bob J. wrote:
> I've been considering going with a PIC24H on my next project (need many
> analog inputs...the PIC24HJ128GP510  has 32 12-bit
> ADC's)<www.microchipdirect.com/ProductSearch.aspx?Keywords=PIC24HJ128GP510>,
> and as I was trying to find some parts to sample I found that the PIC24's
> aren't available as 5V parts.  What's up with that?  That is going to be a
> problem with some of the devices I plan on using with the PIC24, notably
> some 5V SPI devices and an LCD.
>
> Why would Microchip not produce 5V versions of these devices?  

Probably because the process they are using to fab the PIC24HJs isn't
well suited for running at 5V. Also, running at lower voltages allows
features to be smaller, meaning a smaller die, meaning cheaper to fab
Just a guess on my part.

> In
> applications where low power consumption is not a requirement I can't see
> why one would want to migrate their designs to 3V unless I'm missing
> something.

I think the term "migrate to 3V" is a little off. Most of my newest
designs ARE 3.3V, there was no "migration". Heck, some of my designs
even run at lower voltages. A recent board I worked on has a selection
of either 3.3V or 2.5V for the IO drivers.
Most parts these days are 3.3V based. Many are 5V tolerant, but in the
core they mostly run 3.3V. Just look at the ENC28J60 from MChip. It's a
3.3V part. They just made it 5V tolerant on the few IO that might see
5V.

5V in many ways is dead IMHO. I'm surprised it hung around as long as it
did.

TTYL

2006\09\21@024506 by Xiaofan Chen

face picon face
On 9/20/06, Bob J. <spam_OUTrocketbobTakeThisOuTspamgmail.com> wrote:
>
> Why would Microchip not produce 5V versions of these devices?  In
> applications where low power consumption is not a requirement I can't see
> why one would want to migrate their designs to 3V unless I'm missing
> something.
>

They are using different process with the PIC24 and dsPIC33. I think they
are produced by third-party Fabs.

2006\09\21@054719 by Bob J.

picon face
Well, after reading some of Microchip's 3V documentation I see now what the
rationale is, and its exactly as you say Marcel.  Its driven by the fab
process.

I think now the task at hand for me is to figure out how to work with
getting 5V devices to mingle with a 3.3V PIC24.

Regards,
Bob

On 9/20/06, Marcel Duchamp <.....marcel.duchampKILLspamspam@spam@sbcglobal.net> wrote:
{Quote hidden}

> -

2006\09\21@061150 by Michael Rigby-Jones

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>-----Original Message-----
>From: piclist-bouncesspamKILLspammit.edu [.....piclist-bouncesKILLspamspam.....mit.edu]
>Sent: 21 September 2006 05:21
>To: Microcontroller discussion list - Public.
>Subject: Re: [PIC] 5V PIC24?
>
>
>Well, after reading some of Microchip's 3V documentation I see
>now what the rationale is, and its exactly as you say Marcel.  
>Its driven by the fab process.
>
>I think now the task at hand for me is to figure out how to
>work with getting 5V devices to mingle with a 3.3V PIC24.
>

Why not try to use 3volt devices?  There is probably a larger selection of 3v peripherals that 5v these days.

Regards

Mike

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2006\09\21@061417 by Alan B. Pearce

face picon face
>I think now the task at hand for me is to figure out how to work with
>getting 5V devices to mingle with a 3.3V PIC24.

I guess the best way is the FET level shifter shown in the Philips I2C
definition document at http://www.standardics.nxp.com/support/i2c/ (about
2/3 down the page under "Bus Specifications")

2006\09\21@062630 by Michael Rigby-Jones

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>-----Original Message-----
>From: EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu [piclist-bouncesspamspam_OUTmit.edu]
>Sent: 21 September 2006 11:08
>To: Microcontroller discussion list - Public.
>Subject: Re: [PIC] 5V PIC24?
>
>
>>I think now the task at hand for me is to figure out how to work with
>>getting 5V devices to mingle with a 3.3V PIC24.
>
>I guess the best way is the FET level shifter shown in the
>Philips I2C definition document at
>http://www.standardics.nxp.com/support/i2c/ >(about 2/3 down
>the page under "Bus Specifications")

Maybe ok for 1 or 2 lines, but for larger/faster busses a proper level translator is a much neater solution e.g. 74LVC4245

Possibly useful app note: http://www.standardics.nxp.com/support/documents/logic/pdf/an240.pdf

Regards

Mike

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information contained in it may be confidential and/or protected by
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not make any use of this information, or copy or show it to any
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2006\09\21@113326 by Bob J.

picon face
Great info guys, thank you.  I'm going to go ahead and start tinkering with
the PIC24 once I get some samples and am able to fab up a breakout board to
breadboard with.

I haven't seen much on the list regarding using the PIC24's, I imagine
that's due to the packaging being what it is, being non-hobbyist friendly.
Having cut my teeth on the 18F's I've generally found that I've been able to
accomplish whatever I set out to do in assembler.  Some of the features of
the PIC24's definitely are interesting, such as the RTCC, and gobs of ADC's.

Regards,
Bob

2006\09\21@114703 by peter green

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face
if your not too worried about the price per chip then i belive the dspic30f
series are essentially the same as pic24s but with a few extra instructions
and running on 5V.

unfortunately none of the dspic30 series seem to have the analog input count
you wan't, it looks like you'll have to go with the 3.3V part and if
nessacery add level shifting (note though that level shifting may not
actually be needed, check the thresholds of the inputs on the 5V devices and
if the inputs you plan to use on the pic are 5V tolerant).

> {Original Message removed}

2006\09\21@114815 by Jan-Erik Soderholm

face picon face
Bob J. wrote :

> I haven't seen much on the list regarding using the PIC24's,
> I imagine that's due to the packaging being what it is, being
> non-hobbyist friendly.

Note that there are 1 PIC24's in DIP-18 and 3 in DIP-28 in the
line card as "future products". Still 3.3V though...

Jan-Erik.



2006\09\21@230135 by John Chung

picon face
I still don't get it. Why hold on to 5V? Okay some
systems work with 5V. If there wasn't any 5V MCU then
we need TTL.....  At any case, a MCU must forward with
the current voltage requirement which is 3.3 volts....


John

--- Herbert Graf <@spam@mailinglist3KILLspamspamfarcite.net> wrote:

> On Wed, 2006-09-20 at 22:13 -0400, Bob J. wrote:
> > I've been considering going with a PIC24H on my
> next project (need many
> > analog inputs...the PIC24HJ128GP510  has 32 12-bit
> >
>
ADC's)<www.microchipdirect.com/ProductSearch.aspx?Keywords=PIC24HJ128GP510>,
{Quote hidden}

> --

2006\09\22@034558 by Alan B. Pearce

face picon face
>I still don't get it. Why hold on to 5V?

Because there is still a lot of peripheral stuff that uses 5V?

2006\09\22@035739 by Mike Harrison

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face
On Thu, 21 Sep 2006 20:01:33 -0700 (PDT), you wrote:

>I still don't get it. Why hold on to 5V? Okay some
>systems work with 5V. If there wasn't any 5V MCU then
>we need TTL.....  At any case, a MCU must forward with
>the current voltage requirement which is 3.3 volts....


One reason for staying with 5V is that contrrast on  LCDs at 3.3v can be a problem, but in  most
cases the LCD drive voltage can be driven  negative to increase the overall drive - a 5V LCD on a
3.3v supply, with VLCD driven from a simple charge pump, about  -2v after diode drops,  works a
treat.

{Quote hidden}

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