ADC Input Voltage & Vref in imxRT1064.

[jagan_k]

Hi,
    We are using the iMX.RT1064 in our project and we are working on the 12-bit ADC in the imx with the Input voltage - (0 to 3.3V) and Vref as 3.3V.
We are not receiving the expected ADC values while varying the Input voltages and ADC value not attaining the Max value, even the Input Voltage is 3.3V.

Based on the document, VRefH is VDD_ADC & VRefL is VSS. We have connected the VDD_ADC to 3.3V, so the Vref is 3.3V.

Even with the Vref as 3.3V & ADC Vin is 3.3V, we are not receiving max ADC value. We have measured the Input voltage it is 3.3V, with this supply we receiving ADC value of 3800 instead of 4095.
But the same Vin & Vref are followed in LPC1768, we are receiving the expected value in LPC. We have compared ADC's Electrical specs of LPC1768 & imxRT1064, it looks almost same.


Is there any change to be done in the imxRT? And is there any way to verify the Vref in firmware?



Thanks
Jagan K

[jingpan]

Hi @jagan_k ,

Do you use ADC examples in SDK to test? Are you using customer board? What is the input resistor?

Regards,

Jing

[jagan_k]

Hi Jing,
   Thanks for your Support. We have used the ADC examples used in SDK & found the same issue with example code.
    
  We are using the Custom board in which a Output of a Divider Circuit as Input to ADC pin.
 I/P Voltage of the ADC pin will be from 0 to 3.3V


Thanks
jagan K

[jingpan]

Hi @jagan_k ,

If the impedance of the divider is too big, this could happen. Please refer to the attachment.

Regards,

Jing