Microcontroller with 7V supply and I/O tolerance ?

"David" <mangled_us@yahoo.com> skrev i meddelandet
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 ?  :-)

No, as others have mentioned, the cost makes the device unattractive.
To handle 7 Volt inside a transistor, you have to use processes
which are (today) totally unsuitable cost wise
Battery operated equipment is moving in the other direction to conserve
power.

Remember:

    P = C * U^2

So reduction off voltage is the most important factor in battery management.
You can use an regulator to reduce the voltage from a high voltage device.
You do not need to use the high voltage for I/O.




>
> Regards,
>
> David




-- 
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.

> Queestion as topic :  does anyone here know of a microcontroller that
> can operate with supply and I/O between 4 and 7 volts ?

Microchip produces "HV" variants (high voltage) of some of their PIC
chips.  IIRC they work at up to 14V, but at least they are good to
run off 9V batteries.

> Of course I could regulate the supply but then I would also need to
> opto-isolate all the I/O which is not viable.

If you IO doesnt exceed 7V, you dont necessarily have to optoisolate.
The 74VHC family can be used as cheap levelconverter.

Marc

"Norm Dresner" <ndrez@att.net> schrubbelte:

>So, if you had actually used Google

...which I actually did -- but thanks anyway.

-peter

-- 

David wrote:
>>>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 ?

There are some, but not many.

  Highest IO spec I've seen is 100V and 300V on
VERSA HV100, HV300 see
http://www.goalasic.com/productguide.html

  Also Fairchild make uC with 12V regulators, and IIRC Microchip did
an OTP one.  SiLabs hae parts with +/-60V Analog IP pins.

  Atmel's MARC4 family is specified to 6.5V Vcc [operate]

  So higher voltage can clearly be done, but normally the CPU Core is 
not designed for high voltage operation, as it is more power efficent to 
regulate the core power, but maybe offer higher IO voltages.

  STm and Motorola have CMOS+Power FAB processes, that can integrate
uC + PowerMOSFETS for high volume users.

  Anything over 5.5V these days is unusual, but maybe someone will
join Goal in offering a "CPU + ULN2003" in one package ?

  -jg

> > Queestion as topic :  does anyone here know of a microcontroller that
> > can operate with supply and I/O between 4 and 7 volts ?
> 
> Microchip produces "HV" variants (high voltage) of some of their PIC
> chips.  IIRC they work at up to 14V, but at least they are good to
> run off 9V batteries.
> 
> > Of course I could regulate the supply but then I would also need to
> > opto-isolate all the I/O which is not viable.
> 
> If you IO doesnt exceed 7V, you dont necessarily have to optoisolate.
> The 74VHC family can be used as cheap levelconverter.
> 
> Marc

Thanks to Marc and all who responded.  I will investigate the Goal &
Microchip parts and other suggestions re level shifting and
regulation.

Thanks again,

David

mangled_us@yahoo.com (David) writes:
> Queestion as topic :  does anyone here know of a microcontroller that
> can operate with supply and I/O between 4 and 7 volts ?

Microchip PIC16HV family.