ADC digital reading

[skon.1]

Hello,

I'm using the NUCLEO-F722ZE EVB.

Page 155 of the datasheet describes the ADCs characteristics: 

https://www.st.com/resource/en/datasheet/stm32f722ze.pdf

From the NUCLEO-F722ZE schematics I see that VDDA as well as VREF+ are 3.3V. 

VREF- is zero volts (connected to ground).

Based on this values I want to know the following:

1. What's the minimum input voltage I can drive the ADC with and digital value will be read when this voltage is applied ?

1. What's the maximum input voltage I can drive the ADC with and digital value will be read when this voltage is applied ? 

[Uwe Bonnes]

Did you have a look at the datasheet for these values? Did you read the section for the ADC in the reference manual?

[skon.1]

I'm interested in the ADC as well as the DAC.

The only information I was able to find is about the ADC from page 159 in the datasheet:

https://www.st.com/resource/en/datasheet/stm32f722ze.pdf

Where can I find the same information about the DAC ?

[Elkin Granados]

Hi @skon.1​ ,

Checking the tables of the ADC and the DAC there is the infomation that you need:

The maximun voltage that you can drive in an ADC input pin is Vain, the minimun is VSSA/VREF - that usually is tied to ground and the maximun is VDDA/VREF+ in this case 3.3V, check that the maximun value that you can apply to VDDA/VREF+ is 3.6V, a higher voltage could damage the pin.

About the value that you read from the ADC it is a simple calculation, Digital Value = (Vadc pin * 4096) / Vref+, so if the voltage in the ADC pin si 1V then Digital Value = (1V * 4096) / 3.3V = 1241 approximately, now if you want to convert the digital value into a voltage in the micro just make the inverse calculation in your program.

About the DAC there are to options for the minimun and the maximun value, if you use the buffer of the peripheral the minimun value is 0.2V and the maximun is VDDA-0.2V, but without the buffer the minimun value is 5mV and the maximun isv VREF+1LBS. Think about DAC as the reverse of the ADC, so if you want 1V in the DAC output pin you write a value in the DAC of 1241. Of course you should measure the real value because not always is exactly.