Ulf Samuelsson wrote:

> If the choice had bveen made to support the lower voltage flash,
> then this would have affected the maximum clock frequency of the device.
> You can't run the SAM7S from a Lithium cell unless you have
> a voltage regulator stepping up to minimum 3.0V.
> The AT91M40800 will work at 1.8V with external 1.8V flash.
> 

could be the future SAM7L will satisfy his needs

rickman wrote:
> Eric Smith wrote:
>> "rickman" <gnuarm@gmail.com> writes:
>>> Unless there is some clear advantage
>>> to using a part like the AT91M40800, I would expect one of the SAM7S
>>> parts running at 1.8 volts for both core and I/O to be a much better
>>> choice.
>>
>> The datasheet indicates that the AT91SAM7S parts require 3.0-3.6V
>> for the flash memory.  Even just to read it.  Otherwise it would be
>> OK.
>
> Yes, you are right.  They also have a separate VDDIN pin to power the
> LDO.  Seems rather silly that they only offer 1.8 and 3.3 volt IO
> standards given that you have to have 3.3 volts for the part to work
> from Flash.  I guess there is some market for 1.8 volt IOs though.

If the choice had bveen made to support the lower voltage flash,
then this would have affected the maximum clock frequency of the device.
You can't run the SAM7S from a Lithium cell unless you have
a voltage regulator stepping up to minimum 3.0V.
The AT91M40800 will work at 1.8V with external 1.8V flash.

-- 
Best Regards,
Ulf Samuelsson
ulf@a-t-m-e-l.com
This message is intended to be my own personal view and it
may or may not be shared by my employer Atmel Nordic AB 

Eric Smith wrote:
> "rickman" <gnuarm@gmail.com> writes:
> > Unless there is some clear advantage
> > to using a part like the AT91M40800, I would expect one of the SAM7S
> > parts running at 1.8 volts for both core and I/O to be a much better
> > choice.
>
> The datasheet indicates that the AT91SAM7S parts require 3.0-3.6V for the
> flash memory.  Even just to read it.  Otherwise it would be OK.

Yes, you are right.  They also have a separate VDDIN pin to power the
LDO.  Seems rather silly that they only offer 1.8 and 3.3 volt IO
standards given that you have to have 3.3 volts for the part to work
from Flash.  I guess there is some market for 1.8 volt IOs though.

"rickman" <gnuarm@gmail.com> writes:
> Unless there is some clear advantage
> to using a part like the AT91M40800, I would expect one of the SAM7S
> parts running at 1.8 volts for both core and I/O to be a much better
> choice.

The datasheet indicates that the AT91SAM7S parts require 3.0-3.6V for the
flash memory.  Even just to read it.  Otherwise it would be OK.

"Ulf Samuelsson" <ulf@a-t-m-e-l.com> writes:
> AT91M40800 will run downto 1.8V, but
> does not have a lot of fancy features.

No flash memory, though.

I don't require that the flash memory be programmed at 1.8V (though that
would be nice), but I need a part that can run from Flash memory.

Ulf Samuelsson wrote:
> "steve" <bungalow_steve@yahoo.com> skrev i meddelandet
> news:1162693704.760605.61840@b28g2000cwb.googlegroups.com...
> >
> > Eric Smith wrote:
> >> Most of the ARM microcontrollers seem to require 3.0-3.6V supply,
> >> though many have an internal regulator for 1.8V for the core.
> >>
> >> Are there any ARM microcontrollers that can run directly on a
> >> lithium cell (e.g., 2.0 to 3.2V supply), avoiding the need for
> >> a boost regulator or charge pump?
> >
>
>
> AT91M40800 will run downto 1.8V, but
> does not have a lot of fancy features.

It still seems to me that it would be better to add the very small LDO
and run from 1.8 volts regardless of battery voltage.  That should
minimize the current at all voltages and extend battery life over a
design that simply connects the part to the battery and draws higher
currents at the higher voltages.  Unless there is some clear advantage
to using a part like the AT91M40800, I would expect one of the SAM7S
parts running at 1.8 volts for both core and I/O to be a much better
choice.

"steve" <bungalow_steve@yahoo.com> skrev i meddelandet 
news:1162693704.760605.61840@b28g2000cwb.googlegroups.com...
>
> Eric Smith wrote:
>> Most of the ARM microcontrollers seem to require 3.0-3.6V supply,
>> though many have an internal regulator for 1.8V for the core.
>>
>> Are there any ARM microcontrollers that can run directly on a
>> lithium cell (e.g., 2.0 to 3.2V supply), avoiding the need for
>> a boost regulator or charge pump?
>


AT91M40800 will run downto 1.8V, but
does not have a lot of fancy features.

-- 
Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may not be shared by my employer Atmel Nordic AB 

rickman wrote:
> steve wrote:
> > Eric Smith wrote:
> > > Most of the ARM microcontrollers seem to require 3.0-3.6V supply,
> > > though many have an internal regulator for 1.8V for the core.
> > >
> > > Are there any ARM microcontrollers that can run directly on a
> > > lithium cell (e.g., 2.0 to 3.2V supply), avoiding the need for
> > > a boost regulator or charge pump?
> >
> > yes
> >
> > http://www.standardics.nxp.com/news/lpc2800/~LPC2888/#LPC2888
>
> This seems to be an unusual part.  The data sheet is preliminary and
> the press release does not give many details, but it seems like the
> chip includes a DC/DC switching converter.  So a coil and bulk caps are
> still required and is typically the largest components of a switching
> converter.  It is very odd that the data sheet has so little info on
> this circuit.  It is not clear if it is a buck, boost, or a buck/boost
> converter.
>
> I guess we will have to wait...

yes it's a DC/DC converter, see users manual chapter 7

steve wrote:
> Eric Smith wrote:
> > Most of the ARM microcontrollers seem to require 3.0-3.6V supply,
> > though many have an internal regulator for 1.8V for the core.
> >
> > Are there any ARM microcontrollers that can run directly on a
> > lithium cell (e.g., 2.0 to 3.2V supply), avoiding the need for
> > a boost regulator or charge pump?
>
> yes
>
> http://www.standardics.nxp.com/news/lpc2800/~LPC2888/#LPC2888

This seems to be an unusual part.  The data sheet is preliminary and
the press release does not give many details, but it seems like the
chip includes a DC/DC switching converter.  So a coil and bulk caps are
still required and is typically the largest components of a switching
converter.  It is very odd that the data sheet has so little info on
this circuit.  It is not clear if it is a buck, boost, or a buck/boost
converter.  

I guess we will have to wait...

Eric Smith wrote:
> Most of the ARM microcontrollers seem to require 3.0-3.6V supply,
> though many have an internal regulator for 1.8V for the core.
>
> Are there any ARM microcontrollers that can run directly on a
> lithium cell (e.g., 2.0 to 3.2V supply), avoiding the need for
> a boost regulator or charge pump?

yes

http://www.standardics.nxp.com/news/lpc2800/~LPC2888/#LPC2888