microcontroller with built-in op-amp

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I know there are micros with built-in comparators, but are there any
that have a built-in rail-to-rail op-amp suitable for conditioning a
strain-gage bridge sensor and reading the results on an A/D?


-Robert Scott
 Ypsilanti, Michigan
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Re: microcontroller with built-in op-amp

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There are a few but performance is usually somewhat compromised compared to an
external amp.

Re: microcontroller with built-in op-amp
On Wed, 12 Jan 2005 14:58:58 GMT, the renowned no-one@dont-mail-me.com

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Some of the micros with delta-sigma ADCs have PGAs built in that would
be suitable for that sort of application.


Best regards,
Spehro Pefhany
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Re: microcontroller with built-in op-amp

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Check out Cypress' PSOCs. They have field-programmalbe analog gate arrays
with zippy little MCU attached.

Noel


Re: microcontroller with built-in op-amp



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The PSoC fits the bill.  BUT the Op-Amps and the analog have limitations.  It
may or may not work in your application.

The Zippy little MCU is limited by the weak C compiler.  ( code is a little big
and the ROM is a little small)
 (I am told ASM is OK) No bit operands.  the Development environment has a big
learning curve.

It is good for many things,  But not all.



Re: microcontroller with built-in op-amp
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True. But amazing things have been done with them.

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I stick with assembly. I've been burned by c compilers in the past when
code and data spaces are limited.

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I agree.

Noel



Re: microcontroller with built-in op-amp
Hi Robert,
look at www.ti.com for the MSP430 series, there are devices with opamp,
for example the MSP430FG437.

Andreas

Re: microcontroller with built-in op-amp

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  You can also do this using a DAC, and an increasing number of
mixed signal uC now also nclude DACS - see MSC12xx from TI, most SiLabs
C8051Fxx series, some Philips LPC series (etc).
-jg


Re: microcontroller with built-in op-amp

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Not a great idea to amplify such a low level signal inside a micro
banging the rails with digital noise. Your signal to noise ratio will be
huge.

You are better off amplifying with an external op amp,
with a good board layout to minimize noise floor.
Then feed that into a micro with A2D inputs.




Re: microcontroller with built-in op-amp
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A microcontroller on a chip is a too noisy friend to
low-level analog signals, like strain gages.

Could you think the other way around: take an
external very good A/D and use it on the bridge
directly?

For examples, get Linear Technology LTC2420 data sheets
and application notes.

--

Tauno Voipio
tauno voipio (at) iki fi


Re: microcontroller with built-in op-amp
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Take a look at the UTI (Universal Transducer Interface) from Smartec
(www.smartec.nl). This interface almost any type of sensor (bridge,
resistive, capacitive) to a uC. It compensates offset errors and the signal
to the uC is a multi-phase squareware which contains the measured value as
well as the reference value. Extremely good circuit. It is also used to
measue fF capacities in Tunneling Electron Microscopes.

Meindert



Re: microcontroller with built-in op-amp
Thanks to all of you for your very thoughtful comments and
suggestions.  Now I must digest it all to see what it means
for my application, which is a body-mounted humidity logger
for a medical research project.


-Robert Scott
 Ypsilanti, Michigan
(Reply through this forum, not by direct e-mail to me, as automatic reply
address is fake.)

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