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PSoC 4 MCU

Anonymous
Not applicable

 How to get VDAC functionality from PSoC4? 

   

Need programmable votage in range of 0-4 voltage.

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Esteemed Contributor II

PSoC4 provides you with an IDAC which will deliver a programmable current

   

With the help of Ohm's Law U = R * I you can calculate an R that delivers your maximum voltage (4V) at the maximum output current (selectable 306µA or 612µA).

   

 

   

Bob

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Esteemed Contributor

 Keep in mind that the output Z of the IDAC using a R to become

   

a VDAC is the R used to develop the voltage. So if you need a buffered

   

output feed that to an OpAmp configed as a buffer.

   

 

   

Regards, Dana.

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Esteemed Contributor

 Keep in mind that the output Z of the IDAC using a R to become

   

a VDAC is the R used to develop the voltage. So if you need a buffered

   

output feed that to an OpAmp configed as a buffer.

   

 

   

Regards, Dana.

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Anonymous
Not applicable

 Is there any limit on resistance range? How much higher we can go in voltage?

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Esteemed Contributor II

You cannot exceed VDD with a maximum of 5V. Since this will not always work rail-to-rail I woud suggest to expect no more than VDD - 100mV.

   

 Since you are here in PSoC World it would be quite easy for you to set up a project that sweeps your IDAC from lowest to highest and additionally measure with PSoC4's ADC the voltage at that pin. Always good to have a Pioneer kit at hand!

   

There is even an easy way to output the ADC-measures via UART to your PC using 2 wires on the kit and using HyperTerm or PuTTY. That's RAD!!! (Papid Application Design)

   

 

   

Bob

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Esteemed Contributor

The IDAC has a compliance limit it needs to keep the current source in

   

constant current region. From spec sheet -

   

 

   

   

 

   

So max V before the IDAC comes out of regulation, as a source, is Vdd - .8V

   

 

   

if you wanted to test this use the PSOC 4 SAR, at 12 bits it can measure the 8 bit IDAC to 1/16 LSB, +/-

   

 

   

Regards, Dana.

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Esteemed Contributor II

...and I always wandered what "Compliance Voltage" would mean...

   

 

   

Bob

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Esteemed Contributor II

Interesting!!!

   

When I switch from the English explanation in wikipedia to German there is no mention of a characterization alike to the "Compliance Voltage". Might be the reason that I never heard (or understood) that before.

   

 

   

Bob

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Esteemed Contributor

Odd, many semiconductor papers around the world discuss.

   

Very early industrial control as well from vacum tube era.

   

 

   

Many ap notes also.

   

 

   

Dana.

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