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PSoC 5, 3 & 1 MCU

New Contributor II

Hello,

   

 

   

I'm improving a project containing a PSoC 1, switching to PSoC 5.

   

The problem is that PSoC 1 has an instrumentation amplifier up to Three Opamp Topology, allowing dynamical changing of the gain (differential gain + conversion gain). This feature allow to make a fine gain control (< 1) and a big gain control (> 1) too.

   

 

   

With PSoC 5 this feature is still not present. I have only Opamps and PGA that I could connect together to obtain the same configuration.

   

The problem is the dynamically gain control of PGA. I can't get down gain = 1, so this is reduce the performance of my system because I can make a fine gain control.

   

 

   

Is there a similar PSoC 1 component to use with PSoC 5 or alternatively do you have a solution?

   

Best regards

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1 Solution
Honored Contributor II
        Regretfully, PSoC5 has less analog capabilities than PSoC1 (and P6 less than P5), inflation rocks! I don't see other way but using either external trimpot, digital pot or multiplying DAC to fine-tune gain of analog signal chain. If analog signal has low bandwidth (<1kHz), it is possible to trim it down using Modulator component in multiplying mode by multiplying analog input by high frequency PWM of var. duty and filtering output. Theoretically, the switched capacitor block can be used for precision gain tuning, but I am not aware of any such examples.   

View solution in original post

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17 Replies
New Contributor II

Mainly I need the possibility to make a fine gain control between 0.8 and 1.2 after a big gain control (in step x2 for example 2,4,8,16 etc)..

   

I have to convert signals from a magnetoresistance into a 1Vpp signals so, if I set the gain to 8 or 16 lead my output signal to going out specifications. I can adjust my gain of 8 or 16 with another gain control between 0.8 to 1.2..

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Honored Contributor II
        One way would be to use external resistors http://www.cypress.com/blog/psoc-insiders-blog/design-idea-analog-gain-controlled-digitally Is 1V signal being consumed inside PSoC or it is an output for external use?   
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New Contributor II

Hello Odissey,

   

I already thought to place external resistors but I'm using PSoC 5LP in QFN68 where almost all pin are used. Even if I should have the available pins to create a resistors array, I should evaluate if my electronics board has the necessary space.

   

 

   

Furthermore, I'm using a double magnetic resistance  so I need to amplifier two couple of differential signals, so I should place a double array of resistors.

   

 

   

After the amplification, my signals going out from PSoC 5 sourcing an external differential driver where I must have the correct amplitude of 1Vpp.

   

 

   

Can you confirm that no more exist internal in the PSoC 5 a component that manage a fine gain control?

   

 

   

Thanks and regards

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Esteemed Contributor II

Depending on the required frequency / response time / precision

   

Can you use a DAC to output the 1V p-p value per software gain calculation?

   

 

   

Just my two cents

   

Bob

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New Contributor II

Hi Bob,

   

unfortunately I can't use a DAC because the final user takes the 1Vpp signals and use it to interpolate to increase the resolution of the system (he could divide the analog signals up to 2000), so these signals have to be very accurate.

   

 

   

The actually project with PSoC 1 works fine cause we can calibrate a big gain and also a fine gain.

   

I think that maybe the only way to solve this problem is to use only the big gain control by means of PGA and change the power supply dynamically to the MR (with a PWM) in order to changing the amplitude of the original signals..

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Honored Contributor II
        Regretfully, PSoC5 has less analog capabilities than PSoC1 (and P6 less than P5), inflation rocks! I don't see other way but using either external trimpot, digital pot or multiplying DAC to fine-tune gain of analog signal chain. If analog signal has low bandwidth (<1kHz), it is possible to trim it down using Modulator component in multiplying mode by multiplying analog input by high frequency PWM of var. duty and filtering output. Theoretically, the switched capacitor block can be used for precision gain tuning, but I am not aware of any such examples.   

View solution in original post

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New Contributor II

The bandwidth is higher. Is about 30kHz..

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New Contributor II

Hello,

   

could you confirm that in PSoC 5 the SAR ADCs have internal S&H?

   

My goal is to implement two ADC SAR channel to read analog values from the double MR (see above).

   

I have to set the two SAR to 1MSPS and when they going to receive a hw trigger, they start to convert (1 conversion each trigger on "soc" pin).

   

The trigger lets start converting both channel at the same time because the two values are to be used to interpolate sin/cos.

   

I can't use dedicate S&H component because I used all 4 SC/CT blocks to create two InsAmp, but if I well understood, the SAR has internal S&H, isn't it?
Regards

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Esteemed Contributor II

Yes, there is an internal S&H, but it samples only the current channel. The eoc signal indicates when the sampling phase is over and the input can be switched to the next channel.

   

Here is a "trick" to overcome that situation.

   

 

   

Bob

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New Contributor II

Hello Bob,

   

do you mean that there's only one S&H for both two SAR ADC or each SAR ADC has an internal S&H ?

   

 

   

In my device I've got two SAR ADC and I'm going to use both of them (one channel for each ADC), so if each ADC has an internal S&H, I can command both "soc" pin with the same signal to start one conversion at the same time.

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New Contributor II

Bob,

   

I'm implementing InsAmp of figure 2 of AN06319 on PSoC5.

   

My project can't compile the analog routing. Attached my project, could you take a look and explain which is the best configuration regarding the analog pins?

   

Thanks and regards

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Esteemed Contributor II

Cannot open your .zip. Please use

   

Creator->File->Create Workspace Bundle (minimal)
and attach the resulting file.

   

Of course there is a S&H for each SAR ADC 😉

   

 

   

Bob

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New Contributor II

Of course.

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Esteemed Contributor II

Well, most of your pins are locked. I unlocked all of them and built the project without errors. Just let the fitter do its work...

   

 

   

Bob

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New Contributor II

Hi Bob,

   

thanks for the support. I did not noticed about that opportunity. What's the function of "locked" flag?

   

Regards

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Esteemed Contributor II

Locked pins will not be changed by the fitter. When making a pcb it would be fatal when pins change.

   

Do not forget after a successful build to lock the pins or they might change with every new build.

   

 

   

 

   

Bob

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New Contributor II

Ok,

   

thanks.

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