Microcontroller with 7V supply and I/O tolerance ?

"David" <mangled_us@yahoo.com> skrev i meddelandet
news:fdf3b9b2.0410220220.6c8bd885@posting.google.com...
> Hi,
>
> Queestion as topic :  does anyone here know of a microcontroller that
> can operate with supply and I/O between 4 and 7 volts ?  If I could
> have anything I wanted then a SiLabs 8051F320 would be perfect but
> they can only go to 5.25V.  Alternatively almost anything in the TI
> MSP430 series would do at a pinch but they also only seem to support
> supply voltages up to 5.5V max.
>
> Of course I could regulate the supply but then I would also need to
> opto-isolate all the I/O which is not viable.
>
> Many thanks,
>
> David


Since I/O is beteen 4 and 7 volts, why do you not connect the GND of the
Micro to 4 Volts.
Most CPUs will handle that.

(Just kidding ;-)
-- 
Best Regards
Ulf at atmel dot com
These comments are intended to be my own opinion and they
may, or may not be shared by my employer, Atmel Sweden.

"Peter Kannegiesser" <pk-lat@gmx.de> wrote in message
news:qm8in0pbgboai1mto6e35ib7nk8fgu18kt@4ax.com...
> "Norm Dresner" <ndrez@att.net> schrubbelte:
>
> >"Peter Kannegiesser" <pk-lat@gmx.de> wrote in message
> >news:q92in0988biv8609s798c0lfvf9s0og5gf@4ax.com...
> >> Paul Burke <paul@scazon.com> schrubbelte:
> >>
> >> >Oh, and the Motorola MC14500
> >>
> >> Does anyone happen to have a (scanned or original paper) datasheet of
> >> this chip? I've been looking for a veeeery long time to find it.
> >>
> >> I remember that I owned a Motorola databook that contained it but this
> >> has been gone during some of my moves...
> >>
> >
> >    Have you ever heard of Google?
> >
> Thanks for that very new tip -- and what does this get me? I find
> quite a lot of things, but no _datasheet_
>
> It might be that I'm not patient enough, but I've yet to see the
> datesheet... Ok, I confess that I'm sometimes blind :-)
>

I searched for "MC14500" and on the very first page of hits, the second one
is
    http://www.chipdocs.com/datasheets/datasheet-pdf/Motorola/MC14500.pdf

which, if you're registered at chipdocs, would get you a data sheet!

And there's another hit too at
    http://www.radanpro.com/el/dsl?MC14500.pdf
which AFAICT only requires registering and not a fee.

So, if you had actually used Google -- instead of just throwing up your
hands and declaring that you couldn't find it, you'd already have it.

> > Of course I could regulate the supply but then I would also need to
> > opto-isolate all the I/O which is not viable.
> 
> You don't need to opto-isolate, just level-shift.  Many existing ICs can
> do that.  In fact, many PC CPU runs below 2V and level-shift to 3.3V/5V.
> Many microcontroller runs below 2V for much lower operating power. some
> has open-collector outputs to aid lvel-shifting.
> 

I mispoke thanks for pointing that out.  Of course any level-shifting
method would do, not just opto-isolating the I/O.  However I want it
all done on the MCU,  'cos otherwise it'll treble the board area (<
1"" square) and also treble the costs.  I'm certain this can't be an
unusual requirement - is there really no MCU currently available with
higher than 5(ish) volts tolerant I/O ?

Thanks,

David

"David" <mangled_us@yahoo.com> wrote in message 
news:fdf3b9b2.0410220220.6c8bd885@posting.google.com...
> Hi,
> Queestion as topic :  does anyone here know of a microcontroller that
> can operate with supply and I/O between 4 and 7 volts ?  If I could
> have anything I wanted then a SiLabs 8051F320 would be perfect but
> they can only go to 5.25V.  Alternatively almost anything in the TI
> MSP430 series would do at a pinch but they also only seem to support
> supply voltages up to 5.5V max.
> Of course I could regulate the supply but then I would also need to
> opto-isolate all the I/O which is not viable.
> Many thanks,
> David

The old RCA1802 is about it for choices. It runs at up to 10v, so 7 volts 
would not be a problem.
But the old 40 pin .100" spaced pins make for a large chip by today's 
standards.

But if you choose one of the lower power MCU's and run it at 3v ot 3.3v or 
5v with a small voltage regulator,
you can keep the size down. You can use some of the CMOS 14Cxxx series IC's 
as level converters for up to 12-16v max.
I do not know how big you want to make your PCB nor how many I/O pins you 
wanting to use, nor what your going to drive with the I/O pins.
One nifty method is to use a small transistors for both In and Out, since 
they are open collector they could work Ok that way.
You use two transistors Out and two In on the same I/O pin, thus you get a 
non-inverting level shifter. 

> Since I/O is beteen 4 and 7 volts, why do you not connect the GND of the
> Micro to 4 Volts.
> Most CPUs will handle that.

Hi Ulf,  thanks for responding.  

I take it from your answer that Atmel don't have such a chip in their
armoury ?  I'm interested to hear from a chip mfr what the reasons
behind this might be ?  Of course I understand that CPU performance is
all optimised for certain voltages and that device densities would
suffer.  But still... a device with a higher supply and I/O voltage
tolerance must surely have many applications ?  Anything that runs of
batteries would be easier to design, for instance.  So how about
persuading the chaps back at base for us ?  :-)

Regards,

David

On 2004-10-24, David <mangled_us@yahoo.com> wrote:

> I take it from your answer that Atmel don't have such a chip in their
> armoury ?  I'm interested to hear from a chip mfr what the reasons
> behind this might be ?

1) Because higher voltage means higher power, and most of us need
   to minimize power.
   
2) It would require a MASSIVE investment in process design and
   test equipment.  There's no way you could ever sell enough
   to break even.

> Of course I understand that CPU performance is all optimised
> for certain voltages and that device densities would suffer.

That's putting it mildly.  NRE aside, I would think that
geometry restrictions would mean the parts would have to be a
lot more expensive than lower-voltage equivalents.

> But still... a device with a higher supply and I/O voltage
> tolerance must surely have many applications?

Apparently not, or somebody would still be selling them. ;)

> Anything that runs of batteries would be easier to design, for
> instance.

Why is that?  Most cells put out 1.1-1.5V.  It would seem that
lower voltages would be a better answer than higher ones.

> So how about persuading the chaps back at base for us ?  :-)

I wouldn't hold my breath.

-- 
Grant Edwards                   grante             Yow!  Yow! Is this sexual
                                  at               intercourse yet?? Is it,
                               visi.com            huh, is it??

mangled_us@yahoo.com (David) wrote in message news:<fdf3b9b2.0410240417.3c0d02b7@posting.google.com>...
> > Since I/O is beteen 4 and 7 volts, why do you not connect the GND of the
> > Micro to 4 Volts.
> > Most CPUs will handle that.
> 
> Hi Ulf,  thanks for responding.  
> 
> I take it from your answer that Atmel don't have such a chip in their
> armoury ? 

Most Atmel fab processes top at 5.5V/6V.

> I'm interested to hear from a chip mfr what the reasons
> behind this might be ?

Different fab requirements for CPU and IO.

> Of course I understand that CPU performance is
> all optimised for certain voltages and that device densities would
> suffer.  But still... a device with a higher supply and I/O voltage
> tolerance must surely have many applications ?  Anything that runs of
> batteries would be easier to design, for instance.  So how about
> persuading the chaps back at base for us ?  :-)

Nop, can't even get them to provide 5V flash memories, instead of
3.3V/1.8V.  We tried and failed.

> 
> Regards,
> 
> David

mangled_us@yahoo.com (David) wrote in message news:<fdf3b9b2.0410240417.3c0d02b7@posting.google.com>...
> > Since I/O is beteen 4 and 7 volts, why do you not connect the GND of the
> > Micro to 4 Volts.
> > Most CPUs will handle that.
> 
> Hi Ulf,  thanks for responding.  
> 
> I take it from your answer that Atmel don't have such a chip in their
> armoury ?  I'm interested to hear from a chip mfr what the reasons
> behind this might be ?  Of course I understand that CPU performance is
> all optimised for certain voltages and that device densities would
> suffer.  But still... a device with a higher supply and I/O voltage
> tolerance must surely have many applications ?  Anything that runs of
> batteries would be easier to design, for instance.  So how about
> persuading the chaps back at base for us ?  :-)
> 
> Regards,
> 
> David

Well Dave, most chip mfr designs are a result of solving THEIR
problems, not ours (even though their "Mission Statements" would have
you believe otherwise). Or maybe they solve their top buyers (auto
mfr) problems, but thats about it (and they kick and fight the whole
way in any case).

CPU's that work under wide voltages ranges would make our life much
easier, but would cause them big headaches. Likewise for
microcontrollers with floating point, or at least a fixed point CPU
with a friggin divide instruction (i.e., where is the divide ARM?, oh
Thumb2 thanks finally).

But nooooo, they like to make nice sleek simple CPU's that solves all
their problem (the origins of the wacky RISC craze), in return, we
have to pay the price by wasting our time trying to figure out how to
optimize a binary divide algorithm (see related thread in this
newsgroup) all because they want to save some die space so they can
include a 20th serial inteface that no one needs (but is easy to
implement). Or we have to waste our time rewriting/rethinking all our
algorithms to not use a divide. Or deal with the headaches of fixed
point math and the typically non portable C code that goes along with
it(what are we still in the 1970's?).

I'm sure all the reasons why this is so is because it makes the most
sense for FORD or others who buy millions of these chips who require
the lowest recurring cost and thus is less concerned about NRE
(software development). Why if I want floating point do I have to buy
a 388 pin 1 mm ball grid array microcontroller to get it (MPC565 with
has more serial ports then I can count on two hands)? Because its best
for FORD, for embedded products which sell in the thousands or ten's
of thousands, most of chips out there don't make much sense and you
have a snowballs chance in hell changing it. Just my opinion.

"David" <mangled_us@yahoo.com> wrote in message 
news:fdf3b9b2.0410240417.3c0d02b7@posting.google.com...
>> Since I/O is beteen 4 and 7 volts, why do you not connect the GND of the
>> Micro to 4 Volts.
>> Most CPUs will handle that.
>
> Hi Ulf,  thanks for responding.
>
> I take it from your answer that Atmel don't have such a chip in their
> armoury ?  I'm interested to hear from a chip mfr what the reasons
> behind this might be ?  Of course I understand that CPU performance is
> all optimised for certain voltages and that device densities would
> suffer.  But still... a device with a higher supply and I/O voltage
> tolerance must surely have many applications ?  Anything that runs of
> batteries would be easier to design, for instance.  So how about
> persuading the chaps back at base for us ?  :-)
> Regards,
> David

Unfortunately for your design, the entire semiconductor world has been 
shifting to smaller dies sizes, lower power contraints,
and lower voltages. Pretty soon the 1.8v systems will be common place. That 
is what is driving the market now.
As for running off of batteries, many systems run off of one Lithium-Ion 
cell at 3.7v quite readily.
Many other battery powered systems use one 1.2v or two 1.2v cells and use 
DC-DC converters to
generate higher voltages such as for LCD back lighting and such. Thus the 
old four, six and eight cell battery designs have
all been replaced by the one or two cell battery designs.
Flash card devices all run at 3.3v or less now.
So unfortunately there is simply no market for 10v MCU's anymore. The 
manufacturers aren't going to make something
that doesn't make a profit for them. It costs many millions of dollars for a 
factory to tool up to make the chips.
You can't make obsolete chips if no one wants them.
Even if you wanted to buy several million 10v MCU's. none of the 
manufacturers would be able to accomodate you as they
have all been switching to ever smaller die sizes and equipment and no one 
has old chip manufacturing facilities left to make these kind of large die 
high power chips anymore.

On 24 Oct 2004 05:17:17 -0700, mangled_us@yahoo.com (David) wrote:

>But still... a device with a higher supply and I/O voltage
>tolerance must surely have many applications ? 

I do not see much need in a higher supply voltage, but higher I/O
voltages would be nice. I think that the largest problem is due to the
common use of multifunction pins, i.e. pins that can be programmed
both as inputs or outputs, which requires a lot of electronics on the
pin. Designing such pins for high I/O voltages would cause a lot of
reverse biasing problems. 

However, if dedicated input on output pins are used, the outputs could
be simply open collector(drain) types, in which the external I/O
voltage could be quite high, provided that there are no real or
parasitic diodes from the output pin (collector/drain) to the Vdd. If
the pin can sink sufficient currents (>20 mA) LEDs and small relays
could be driven directly. 

On the input side a high current protection diode would be required
between each input and Vdd and the input can be used as voltage input,
if the input voltage is always between 0 and Vdd or as a current
input, with an external series resistor, if the input voltage can
swing above Vdd. An extra resistor from input to ground may be needed
to move the "low" state threshold sufficiently low.

A CPU with a low internal power consumption can be driven with a
series resistor and a shunting zener from any voltage. The zener
should keep the Vdd below the maximum allowed Vdd and should be big
enough, so that it can also dissipate the total worst case input pin
current flowing trough the external series resistors through the input
protection diodes to Vdd and through the zener to ground

As such, I do not see a problem if the CPU core Vdd is quite low
(1.5-3.3V) but it sure would be nice to have (high voltage tolerant)
_current_ inputs and outputs (instead of voltage I/O).

Paul