Analog inputs

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Anonymous
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Hello all,

   

I am working with a PSoc3 chip.  First time using the PSoC, and I am wondering can I send a sine wave into an analog input to a low pass filter inside the PSoC?  Since the PSoC is running at 3.3vdc the sine wave will canter on 1.5vdc and swing approximately 1vp/p.

   

 

   

Is this allowable or is the analog input DC level only?  Also, if the answer is YES that I can send a sinewave into the device, can I take th eoutput of my PWM, and send it through an internal integrator and output a sine wave?

   

 

   

Thank you in advance.

   

 

   

Jim

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HeLi_263931
Level 8
Level 8
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Yes, you can send in a sine wave to the PSoC3 - its inputs are perfectly capable to handle AC inputs (up to several MHz, depending on the voltage levels). But you cannot go below ground or above Vdda with your signal - but your proposed signal would be fine even with 3.3V Vdda.

   

I think there is no internal integrator, but you should be able to build one by yourself using the inernal OpAmps and some external capacitors / resistors. Or you go experimental and digitize the signal and feed it into the digital filter...

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ETRO_SSN583
Level 9
Level 9
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Always examine data sheets to see if you are working withg R-R Inputs

   

and outputs, otherwise limited CM range will limit pk-pk swings.

   

 

   

To offset signals into PSOC you can ac couple to a simple divider that

   

supplies the offset to the input. Or you can use the following which eliminates

   

couplig cap, just uses two R's -

   

http://electronicdesign.com/analog/use-excel-calculate-d-level-shifter-resistor-values

   

 

   

Excel spreadsheet to calc values attached.

   

 

   

For PWM integrator, a simple RC network offten surfices. This ap note discusses tradeoff of

   

settling time and ripple in the RC filter.

   

 

   

http://www.ti.com/lit/an/slyt076/slyt076.pdf

   

 

   

 

   

Regards, Dana.

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