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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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PSoC 3
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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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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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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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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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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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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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@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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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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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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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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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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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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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 -
Regards, Dana.
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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.