Setting reference voltages for the i.mx7 ADCs.

[dennis3]

I'm looking at directly using the built in ADCs on the i.mx7 in our project.

In the Reference manual for the i.mx7d board it mentions the ADCX_inX pins w/ 2 ADCs and 4 inputs each.  I see in the reference board schematic where these are connected to a header and brought into the CPU except for the one pin connected to the mikrobus.

It also mentions ADC_VREF[H/L] for the voltage high and low reference.  I can't find these inputs in the reference schematic or the data sheet though.  The only pins I see other than the inputs are the 1.8V power supply and pcap inputs.  

So the question is, how does one set the reference voltage for the ADCs?  I want to measure up to 12V for instance.

[Yuri · Accepted solution]

Hello,

  The ADC VREF relates to VDDA_ADC1_1P8 and VDDA_ADC2_1P8.

The ADC VREFH is internally connected to VDDA_ADCx_1P8 and VREFL is connected to GND.

Have a great day,

Yuri

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button. Thank you!

[dennis3]

Thanks Yuri.   I verified in the data sheet those pins are 1.8V only.  I'll look for a way to use them as is or just find an external companion chip to do what I need.