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From: MooseFET on 14 Jun 2010 21:39
On Jun 15, 2:42 am, n...(a)puntnl.niks (Nico Coesel) wrote:
> MooseFET <kensm...(a)rahul.net> wrote:
>
> >I have been looking at the Analog Designs and NXPs and a few other
> >ARM chips. Does anyone have much experience with using an ARM
> >near analog workings?
>
> >My main requirements (in no order) are:
>
> >(1) Easy to develop and design with.
>
> NXP. A serial port is enough to program it.
>
> >(2) Low power for a given clock speed.
>
> LPC1100 series. AFAIK these also have an internal RC oscillator (1%
> accuracy).
>
> >(3) Low amounts of electrical noise.
>
> >The processor will be an inch away from signals down in the 1mV
> >range.
>
> That shouldn't be a problem with proper decoupling.

It often is. a problem with 1mV signals. Note that I didn't
say that the noise was 1mV. Thats the signal.


From: MooseFET on 14 Jun 2010 21:49
On Jun 15, 2:01 am, Joerg <inva...(a)invalid.invalid> wrote:
> MooseFET wrote:
> > I have been looking at the Analog Designs and NXPs and a few other
> > ARM chips. Does anyone have much experience with using an ARM
> > near analog workings?
>
> > My main requirements (in no order) are:
>
> > (1) Easy to develop and design with.
>
> > (2) Low power for a given clock speed.
>
> Might want to consider one with very fast wake-up that can be placed
> into sleep mode a lot.

The NXP parts and a few others seem to be able to idle
between interrupts and get going again fairy fast. This
will save some power.

>
> > (3) Low amounts of electrical noise.
>
> > The processor will be an inch away from signals down in the 1mV
> > range.
>
> > Any ideas or warnings?
>
> Yeah, use the 80C51 architecture since they won't go away :-))

I started with a Silabs part. It doesn't quite have enough
through put.


> But seriously, main things are, regardless of uC type:
>
> a. Common and full ground plane. Full VCC plane if you have the luxury
> of a 4+ layer board.

I will have internal layers so I can put a Vcc plain under the
micro and a v-analog under the analog parts. I had already
decided on this much.


>
> b. Tuck the crystal really close to XIN and XOUT, mount 1M or whatever
> starter resistor farther away.

I think I will be running on an external clock that is piped in
on a connector. I may use a HC14 or the like locally to
clean it up. Multiple cards will share one clock so that
they all agree on exactly what 1Hz is.



> Not the other way around. You wouldn't
> believe how often that is done wrong.
>
> c. Bypass caps really close to VCC pins but to a guy like you that'll be
> obvious anyhow (but maybe not to other readers). I've often seen lengthy
> skinny traces to bypass caps, they just left the CAD at the 10mil
> default. So if someone else does the layout that's a point to watch.

I often put extra bypassed on the back too.

>
> > BTW: For now I have given up on Analog's because they
> > appear to be going out of that business.
>
> Wow. Out of the uC biz or just ARM?

It was a false impression I got from the fact that they
never answered a simple question about the part. I
got a responding e-mail from the robot and then over
a week of nothing and then a note asking me to resend
the question because of a technical problem with the
web site and then another long delay. I bugged them
a gain and finally got a non-answer from a human.
They appear not to be going out of the processor
business on purpose. If they don't fix their problems
with answering questions, however, the result may
be the same.



>
> --
> Regards, Joerg
>
> http://www.analogconsultants.com/
>
> "gmail" domain blocked because of excessive spam.
> Use another domain or send PM.

From: Michael A. Terrell on 15 Jun 2010 11:17

"Charlie E." wrote:
>
> Rumor I heard had hit Wall Street was that Apple was going to buy ARM
> holding! If so, all those other ARM processors can probably say
> bye-bye... ;-)


Another rumor was that Apple was going to buy MOS Technology to keep
anyone from getting any 6502 processors. While they were talking to the
media, Commodore bought MOS Technology. :)


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
From: krw on 15 Jun 2010 23:41
On Mon, 14 Jun 2010 18:35:51 -0700, Charlie E. <edmondson(a)ieee.org> wrote:

>On Mon, 14 Jun 2010 11:01:04 -0700, Joerg <invalid(a)invalid.invalid>
>wrote:
>
>>MooseFET wrote:
>>> I have been looking at the Analog Designs and NXPs and a few other
>>> ARM chips. Does anyone have much experience with using an ARM
>>> near analog workings?
>>>
>>> My main requirements (in no order) are:
>>>
>>> (1) Easy to develop and design with.
>>>
>>> (2) Low power for a given clock speed.
>>>
>>
>>Might want to consider one with very fast wake-up that can be placed
>>into sleep mode a lot.
>>
>>
>>> (3) Low amounts of electrical noise.
>>>
>>> The processor will be an inch away from signals down in the 1mV
>>> range.
>>>
>>> Any ideas or warnings?
>>>
>>
>>Yeah, use the 80C51 architecture since they won't go away :-))
>>
>>But seriously, main things are, regardless of uC type:
>>
>>a. Common and full ground plane. Full VCC plane if you have the luxury
>>of a 4+ layer board.
>>
>>b. Tuck the crystal really close to XIN and XOUT, mount 1M or whatever
>>starter resistor farther away. Not the other way around. You wouldn't
>>believe how often that is done wrong.
>>
>>c. Bypass caps really close to VCC pins but to a guy like you that'll be
>>obvious anyhow (but maybe not to other readers). I've often seen lengthy
>>skinny traces to bypass caps, they just left the CAD at the 10mil
>>default. So if someone else does the layout that's a point to watch.
>>
>>d. Unused pins: Either as inputs with pull-down, or outputs with "low"
>>written to their port register bit.
>>
>>e. AC terminate longer traces that can switch during signal acquisition.
>>Or bury them if multi-layer.
>>
>>
>>> BTW: For now I have given up on Analog's because they
>>> appear to be going out of that business.
>>
>>
>>Wow. Out of the uC biz or just ARM?
>Rumor I heard had hit Wall Street was that Apple was going to buy ARM
>holding! If so, all those other ARM processors can probably say
>bye-bye... ;-)

All Billion of 'em? ;-) I had a rep bring yet another ARM wannabe company's
FAE around today. "That's nice; get in line". These guys were selling low
power. Ok, but the rest of the stuff takes a lot more than the DSP now.

From: Fred Bartoli on 16 Jun 2010 03:28
MooseFET a �crit :
> On Jun 15, 2:42 am, n...(a)puntnl.niks (Nico Coesel) wrote:
>> MooseFET <kensm...(a)rahul.net> wrote:
>>
>>> I have been looking at the Analog Designs and NXPs and a few other
>>> ARM chips. Does anyone have much experience with using an ARM
>>> near analog workings?
>>> My main requirements (in no order) are:
>>> (1) Easy to develop and design with.
>> NXP. A serial port is enough to program it.
>>
>>> (2) Low power for a given clock speed.
>> LPC1100 series. AFAIK these also have an internal RC oscillator (1%
>> accuracy).
>>
>>> (3) Low amounts of electrical noise.
>>> The processor will be an inch away from signals down in the 1mV
>>> range.
>> That shouldn't be a problem with proper decoupling.
>
> It often is. a problem with 1mV signals. Note that I didn't
> say that the noise was 1mV. Thats the signal.
>
>

Oh, 1mV is plentiful.

I'm currently working on a 1uV level signal board lost in volt level CM,
with onboard really sub ppm distortion level mid-power amplifiers @
50kHZ/10V, 1 FPGA, a bucket load of PWMs, 1.5MSPS 16b ADC and DACs, just
one 4"x6" PCB, has to work up to 85�C, and so and so...

And we're expected to go right on the first pass :-)

Yes, 1mV is plentiful :-)


--
Thanks,
Fred.
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