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From: MooseFET on 14 Jun 2010 10:06

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.

(3) Low amounts of electrical noise.

The processor will be an inch away from signals down in the 1mV
range.

Any ideas or warnings?

BTW: For now I have given up on Analog's because they
appear to be going out of that business.
From: MooseFET on 14 Jun 2010 13:58
On Jun 14, 7:06 am, 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.
>
> (2) Low power for a given clock speed.
>
> (3) Low amounts of electrical noise.
>
> The processor will be an inch away from signals down in the 1mV
> range.
>
> Any ideas or warnings?
>
> BTW:  For now I have given up on Analog's because they
> appear to be going out of that business.

I may have got it wrong about Analog going out of the business.
At least I don't think it is on purpose. They just don't have
complete documentation and can't seem to answer questions
about timing on the built in DACs.
From: Joerg on 14 Jun 2010 14:01
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?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
From: Nico Coesel on 14 Jun 2010 14:42
MooseFET <kensmith(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.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico(a)nctdevpuntnl (punt=.)
--------------------------------------------------------------
From: Charlie E. on 14 Jun 2010 21:35
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... ;-)

Charlie
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