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PICList Thread
'Internal Oscillators'
1998\01\27@132628 by Charles Laforge

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Hi All

I was wondering if anyone here (Microchip People?) know if Microchip
plans to offer internal oscillators on devices other than the PIC12CXXX.
Seems like logical thing to do.  Probably bring the cost of many
applications down, probably more reliable, simpler circuits..... I'm
just looking for your opinions here... so give em to me... but not too
hard.

Later

Charles

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1998\01\27@133833 by John Bellini

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They are coming out with a new processor that has a internal oscillator.
I believe that it is the16C40X or 16C4XX series.  It is very similar to
the 16C715, and 72.  I believe that it also has a PWM.

> {Original Message removed}

1998\01\27@142545 by Charles Laforge

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Hi Again

I missed that one and looking at the line card it looks like I should
have looked a little closer before asking that question.  There are 10
devices listed under "Future Products" which will have an on board
oscillator.  Does anyone have any info on release dates?

Later,

Charles

(Thanks Dave)

{Quote hidden}

<EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
>> >> Subject:      Internal Oscillators
>> >> To: PICLISTspamspam_OUTMITVMA.MIT.EDU
>> >> Content-Length: 488
>> >> X-Lines: 15
>> >>
>> >> Hi All
>> >>
>> >> I was wondering if anyone here (Microchip People?) know if
Microchip
>> >> plans to offer internal oscillators on devices other than the
>> PIC12CXXX.
>> >> Seems like logical thing to do.  Probably bring the cost of many
>> >> applications down, probably more reliable, simpler circuits.....
I'm
>> >> just looking for your opinions here... so give em to me... but not
>> too
>> >> hard.
>> >>
>> >> Later
>> >>
>> >> Charles
>> >>


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1998\01\27@154833 by Mauro, Chuck

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Charles,

Thanks for bringing this up Charles - I think it's a great topic.

From my experience with working directly with Microchip, I'd say that
there is an excellent chance they will do this - eventually (measured,
unfortunately, in several years of time - but the success of the 12CXXX
family already should have convinced them to offer such a version in all
the PIC families).

I designed a very high volume product around the 12C509 (millions of
units/yr., although, it hasn't shipped - yet -), and did EXTENSIVE lab
testing on the internal oscillator - it's a pretty rock-solid design.
I've even met with Microchip directly, and worked with the
manufacturing/test engineers to better characterize and fine tune our
oscillator requirements in our particular application.  (BTW, don't
expect to ever be able to talk to these guys yourself unless you're an
incredibly large volume customer - and then only maybe...)  I'm not
saying that they changed anything for us, but we had a much more
guarantee-able design after they "ran the numbers" for us (read: truly
characterized the oscillator through extensive wafer testing).

I firmly support you in your appeal to Microchip to increase the number
of devices that contain an internal RC oscillator.  I think everyone
benefits.  But - and everyone else out there should be aware of some
important issues when applying this particular feature of any PIC -
ESPECIALLY when it is first introduced to us (and even more importantly
when devices are made available in "Engineering" type samples):

1)  Any new chip they apply the internal oscillator technology to needs
to be FULLY CHARACTERIZED by Microchip before I'd EVER use it.  They
typically SIMULATE the design and release preliminary data sheets with
projected device characteristics...  Things (osc. characteristics) will
likely change after they build a few wafers and test for process
corners...  For me, after they had performed serious wafer test, I found
that the projected osc. characteristics became WORSE...  But,
fortunately in my case, I was able to find a way around it.

2) Any of your designs need to seriously take into consideration:

 a) Temp range,
 b) Typical Vdd operating point and range (especially supply
regulation).
 c) +/- 3 sigma process variation (at least) of the chip.

These parametrics will affect the oscillator frequency more than
anything else...

3) If you need to guarantee better than a 2.5%-3% tolerance on Fosc over
ALL operating conditions, you're better off using a resonator or xtal,
because you're sure to see  the corners of their process tolerances in
any kind of volume...


To more directly address your original points:

1)  I saved about 25-30 cents [includes all costs] per widget by using
the internal RC osc.  This includes all direct, indirect and typical
hidden costs (p.c. real estate needed, pick and place costs, component
stocking costs, improved reliability, etc.).  Keep in mind that my
volume is (was) between 20-30 MM units/yr for a several year period.
Your savings will likely be even higher (perhaps as much as $1?).

2) My design was far more elegant because of the internal osc. design...

3) And reliable...

4) I also needed all the I/O I could get in an 8 pin device.  This is
the only way to maximize I/O capabilities of the 12CXXX family...

5) I also believed it may have helped in reducing my total RFI emmision
signature for various reasons that I can't go into here...

So, from a very real world example (sorry - can't disclose what the
widget is or does - due to one of those annoying proprietary/trade
secret clauses in an employee exit agreement), I can assure you the
internal RC osc. is a great way to go if you do not have strict
real-time timing issues.  I suspect that a vast majority of
personal/hobby/non mission-critical PIC projects could probably get away
with using this type of cost-improving oscillator.

I just wish the folks at Microchip would consider using a better (more
temperature and voltage stable) internal osc. technology.  I know for a
fact that if they wanted to, they could tighten the tolerances to under
1%, and not necessarily at higher chip cost (I've researched the various
fundamental methods, and it's quite doable).

SO: HOW ABOUT IT MICROCHIP???


Chuck Mauro

> {Original Message removed}

1998\01\27@192516 by Morgan Olsson

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Riht now, I«m prototyping a project using a PIC14000.
I use the on-chip oscillator and it works well.
The datasheet are still preliminary (from 1996!),
but drift etc I can compensate for in programing.
/Morgan O.

{Quote hidden}

Morgan Olsson, MORGANS REGLERTEKNIK, Sweden, ph: +46 (0)414 70741; fax 70331
-

1998\01\28@011528 by Steve Baldwin

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> >From my experience with working directly with Microchip, I'd say that
> there is an excellent chance they will do this - eventually (measured,
> unfortunately, in several years of time - but the success of the 12CXXX
> family already should have convinced them to offer such a version in all
> the PIC families).

I would also say that Scenix may provide them with some extra incentive to
do this, as they have the internal osc feature as well (also an 8 bit
divider down to 32kHz which is quite a good idea).

> 3) If you need to guarantee better than a 2.5%-3% tolerance on Fosc over
> ALL operating conditions, you're better off using a resonator or xtal,

The Scenix datasheet mentions 8%. Not that it really matters. Either you
need time accuracy (resonator) or you don't (Ext/Int RC). I don't really
care if I debounce a button for 30ms or 50ms if I'm using it to turn on a
relay or light bulb.
As you point out, the real estate saving is significant. An HC49U crystal
is bigger than the 12C509 and if you go to a smaller footprint part, the
price jumps substantially.
They've wet our appetite. Now we want more !  :-)

> 5) I also believed it may have helped in reducing my total RFI emmision
> signature for various reasons that I can't go into here...

It would be interesting to see some data on that. (Not from you obviously.
You'd have to shoot me)
I'd like to see a comparison between Xtal, external RC and internal osc.
Just as a guess, I wouldn't be suprised if the external RC was the worst.
Anyone have the right gear ?

Steve.

======================================================
 Very funny Scotty.  Now beam down my clothes.
======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680                email: @spam@stevebKILLspamspamkcbbs.gen.nz
New Lynn, Auckland           ph  +64 9 820-2221
New Zealand                  fax +64 9 820-1929
======================================================

1998\01\28@203609 by Wayne Foletta

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Chuck:

Yes, you are right!  Low TC internal IC oscillator technology is
available - since the early 80's.

Since you have close contact within Microchip you should suggest they
hire a sharp analog engineer (or get a cross-license) from a top analog
IC house - like Analog Devices, Dallas Semiconductor, or Maxim. They
have oscillators cells, like their bandgap references and charge
transfer A/Ds, that give ppm performance over temperature. They know
about die attach, packaging parameter shifts and how to trim with laser
and e-squared trimming.

Microchip may be too digitally inbred to know the proven production
solutions are out there.

- Wayne Foletta
BMI - Saratoga, CA

{Quote hidden}

> > {Original Message removed}

1998\01\29@090111 by lilel

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I would hope that Microchip would focus on two items:  internal
oscillators and on-chip brownout protection.  I am always having to
add external components to the 12Cxx family for brownout protection.
I am using the 12Cxx parts in a couple of high volume low cost
applications, where every penny counts.  Unfortunately every I/O line
counts, too, and eating up one pin just for brownout protection on a
devbice with 6 I/O is expensive!  Sometimes it is a show-stopper.








> Hi All
>
> I was wondering if anyone here (Microchip People?) know if Microchip
> plans to offer internal oscillators on devices other than the
> PIC12CXXX.
Best Regards,

Lawrence Lile


'Internal Oscillators'
1998\02\03@105230 by lilel
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> I would have thought it would be possible to apply brownout
> protection via Vcc rather than MCLR, in other words you can imagine
> a brownout protection circuit that in essence consisted of a low
> dropout regulator (I believe you can get devices with <100mV
> dropout) controlled by a brownout circuit that in the event of a
> brownout would pull Vcc to 0V and leave it there until the main
> supply returned to normal.

This might work.  Why in the heck is this not built into regulators
in the first place? I have always wondered.

{Quote hidden}

THe problem comes when the device is first turned on, there has not
bveen enough time to charge up the backup capacitor yet.  If a
brownout occurs at this time, or is still occurring after the cap has
discharged, then the micro can go into LALA land.

Maybe this is OK in a toy or a VCR controller.  I work with driving
heating elements, and those can be very dangerous if the micro gets
stuck while one is turned on.  A definite brownout circuit that pulls
MCLR down always halts the processor, and that's the insurance I
need.
Best Regards,

Lawrence Lile

1998\02\03@114825 by Joe Little

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    I work with driving heating elements, and those can be very dangerous if
    the micro gets stuck while one is turned on.  A definite brownout circuit
    that pulls MCLR down always >>>>>>>halts the processor,<<<<<<<< and that's
    the insurance I need.

    ------

    I decided to connect the reset line from the watchdog and micro to the
    heater control latch. Then a reset from any source would clear the heater
    control bits, and explicitly turn the heaters off.  This was an additional
    level of protection I decided was necessary.  My competeters product
    depends on the micro's power up routine to get the heaters turned off.
    What if the micro never re-starts???? lots of smoke.

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