How to get VDAC functionality from PSoC4?
Need programmable votage in range of 0-4 voltage.
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).
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.
Is there any limit on resistance range? How much higher we can go in voltage?
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)
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, +/-
...and I always wandered what "Compliance Voltage" would mean...
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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.
Odd, many semiconductor papers around the world discuss.
Very early industrial control as well from vacum tube era.
Many ap notes also.