microcontroller with built-in op-amp

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

On Wed, 12 Jan 2005 14:58:58 GMT, no-one@dont-mail-me.com (Robert Scott) wrote:

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

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

On Wed, 12 Jan 2005 14:58:58 GMT, the renowned no-one@dont-mail-me.com
(Robert Scott) wrote:

>
>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?

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
-- 
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Robert Scott wrote:

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

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

Noel

Hi Robert,
look at www.ti.com for the MSP430 series, there are devices with opamp, 
for example the MSP430FG437.

Andreas

Robert Scott wrote:

> 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?
> 
  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

"Robert Scott" <no-one@dont-mail-me.com> wrote in message 
news:41e53ad3.9061181@news.provide.net...
>
> 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?

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.

Noel Henson wrote:

> Robert Scott wrote:
>
> >
> > 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
> > (Reply through this forum, not by direct e-mail to me, as automatic reply
> > address is fake.)
>
> Check out Cypress' PSOCs. They have field-programmalbe analog gate arrays
> with zippy little MCU attached.
>
> Noel

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.

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

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

"Tauno Voipio" <tauno.voipio@iki.fi.NOSPAM.invalid> wrote in message
news:KDpFd.37$%P.12@read3.inet.fi...
> Could you think the other way around: take an
> external very good A/D and use it on the bridge
> directly?

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