INSAMP IN PSOC3/PSOC5

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Anonymous
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Does the PsOC 3 or PsOC 5 InsAmp available?

   

I haven't seen it in the Analog components. The PsOC 1 has InsAmp with two and three opamps.

   

How is this possible?

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Anonymous
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Seems to be the PsOC 3 and PsOC5 is still borning and rising. In  fact many datasheets are

   
   

uncomplete ("PRELIMINARY") so there's some user modules as INSAMP or radio frecuency are available into

   
   

PsOC 1 and isn't  into PsOC 3 and PsOC5.

   
   

Even so, there still been alternative solutions.

   
   

You can find several  ways to do INSAMP it in paper AN60319.

   
   

http://www.cypress.com/?rID=40987

   
   

How anyone answer me I do it.

   
   

I love myself.

   
   

Thanks everybody. 

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Anonymous
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I think the reason why they don't put an instrumentation amplifier in PSoC 3 and 5 is because in most cases it's not needed. You can consider it is embedded in the sigma-delta ADC as it has a difrential amplifier with High CMRR and high input impedance.

   

The main problem for my project is the input offset voltage (±0.1mVfor PSoC 3). Can you tell me if it is possible to perform offset correction and how could I do it?

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Bob_Marlowe
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Have a look at this KB-article: http://www.cypress.com/?id=4&rID=43218 

   

 

   

Bob

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ETRO_SSN583
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This might help -

   
   

 

   
   

http://www.cypress.com/?docID=35630

   
   

 

   
   

Regards, Dana.

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Anonymous
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Hi mmoron,

   

We can easily create an instrumentation amplifier with 2 PGAs and an OP-Amp of PSoC3. THe CMRR will depend on the precision of the external resistors (around the Op-amp) you use.

   

 

   

Regards,

   

Praveen

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Anonymous
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Hi Quijote,

   
   

We can easily perform offset cancellation using the offset correction register. Refer the ANNote that the max spec is 100uV. In most cases this value is less than 30uV.

   
   

 

   
   

In addition to the link posted, see the link below

   
   

http://www.cypress.com/?docID=32630

   
   

 

   
   

Regards,

   
   

Praveen

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Anonymous
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I cant acheive howe do you solve INSAMP problem.

   

I need to reduce common-mode signal and amplified main signal.so i must use deferential in-put amplifier like INSAMP.

   

hawe can create something like INSAMP?

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Anonymous
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        How about this? Not Tested!   
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ETRO_SSN583
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The problem with using PGA's in a IA solution is PGA gain inaccuracy

   

from one PGA to another degrades CMRR significantly. A quick DC

   

analysis will show you this. And non matching PGA to PGA AC res-

   

ponse adds to the problem.

   

 

   

The PGA G error in datasheet 2.0 shows +/- 10% at G = 50, */- 2% at

   

G = 1. This would at either extreme produce very poor IA CMRR performance.

   

And this is DC specs.

   

 

   

You have to set goals for G desired, CMRR, DC specs, AC specs,  and

   

then back into the design.

   

 

   

The best approach will be a precision R array external and use 3 OpAmps internal.

   

 

   

Some references to make calculations -

   

 

   

Regards, Dana.

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Anonymous
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        How's next? Still Not Tested!   
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ETRO_SSN583
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Correlated Double Sampling does not produce CMRR but does yield very

   

high offset, drift, noise reduction, if that is more of the problem you might

   

be having. See ap notes attached, one on CDS,m the other on signal chain

   

calibration.

   

 

   

Regards, Dana.

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Anonymous
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        The Setting of my first post was wrong. (1) Each PGA gain have to set greater than 2. (2) Vref have to set Vdda/2 (most wide input range) Here is a simulation chart.   
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ETRO_SSN583
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@PSoC73, the use of the PGA degrades CMRR performance due to

   

PGA to PGA G matching, which is very poor in terms of differential amp

   

performance. If you dropped the PGAs, just used the R array and an OpAmp,

   

at least you could get good CMRR, at the expense of input Z which would

   

produce some CMRR error associated with source Z imbalance.

   

 

   

Do the DC analysis, or look at earlier refeneces I posted, and that will show

   

you this. A quick analysis could be done in MATLAB or by hand.

   

 

   

Regards, Dana.

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Anonymous
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        Hi Dana-san "Konbanwa" Thank you. Three OP amp type is Bundle02.zip. I'm not worry, Becouse when I design a INS-AMP application, I'll use the proper INS-AMP outside of PSoC.   
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ETRO_SSN583
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To close this out LTC did an excellent ap note on CMRR vs finite CMRRamp

   

and R ratios. You can quickly see that to get 60 db of CMRR is not doable in

   

PSOC for a number of reasons, except maybe at room temp. Thats in a single

   

diff amp configuration. To implement the 3 OpAmp configuration PGAs in the

   

IA input stage are out of the question, unless CMRR of << 40 db interests you.

   

 

   

www.google.com/url     Design Note 1023 LTC

   

 

   

Note ap note did not cover T and V and aging effects, but equations can lead you to analyzing that.

   

Perfect problem for MatLab.

   

 

   

Regards, Dana.

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Anonymous
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        The application that use INS-AMP needs much good specifications, CMRR, Vos, linearity, and good amplitude precision. I recently use this chip often. AD8253: Which has decade amplitude 1/10/100/1000, controled by digital gain pins. CMRR is 100dB(minimum) Offset drift is 1.2uV/C(maximum). [ http://www.analog.com/en/specialty-amplifiers/instrumentation-amplifiers/ad8253/products/product.htm... ]   
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ETRO_SSN583
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Other vendors as well -

   

 

   

      focus.ti.com/paramsearch/docs/parametricsearch.tsp     TI/National

   

www.linear.com/products/instrumentation_amplifiers       LTC

   

www.intersil.com/en/parametricsearch.html                         Intersil

   

 

   

Precision R networks to make a diff amp in PSOC 3/5 -

   

 

   

parametric.linear.com/precision_resistor_network            LTC

   

www.maximintegrated.com/datasheet/index.mvp/id/3255    Maxim

   

www.vishay.com/networks-and-arrays/resistor-networks/     Vishay

   

 

   

Regards, Dana.

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Anonymous
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I couldn't open your files. my application open just c fiels.

   

about insamp problem you just use external insamp?

   

Is ir the only possible way?

   

I need to amplify it about 1000 times & reduce commen mode signal.

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Anonymous
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        Hi tar, Which file you couldn't open?   
If is it my bundle files I could be upload again.   
Around INS-AMP, take a look this article, Real instalation is here.   
[ http://www.cypress.com/?app=forum&id=2492&rID=82151 ]   
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Bob_Marlowe
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You should download PSoC Creator latest version from the Cypress website for free, it is able to handle the c-files AND the schematics for the PSoC3. Unzip the downloded file from the previous post into a new directory and open the project-file by double-clicking on it.

   

 

   

Bob

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ETRO_SSN583
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If you need that much G then you have no alternative but to use an external

   

IA from a vendor, like the links I posted.

   

 

   

Also not knowing the device/load cell/sensor you are trying to condition and the

   

CM environment you are in, or for that matter design goals, such as absolute

   

accuracy vs relative accuracy, drift, noise,  its hard to recommend solutions for you.

   

 

   

Last if you are noise or drift challened, consider CDS as part of the solution -

   

 

   

japan.cypress.com/

   

 

   

Regards, Dana.

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Anonymous
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Hi,

   

 

   

I would like to ask why you are using 2 PGAs & 1 OPAMP from PSoC for the instrumentation implementation ?

   

Shouldn't be better to use 3 OPAMP (components) , since the CMRR is better than the one of the PGA PSoC components. 

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