iMXRT ADC reading

[ancymuhammed]

I am using iMXRT1176 in one of our project. Battery voltage (6.4V to 8V) has to be monitored using the internal ADC. We had connected the battery voltage to pin GPIO_AD_08 through a voltage divider 200k & 56.2K. We had seen voltage drop at the input of the ADC. If the battery voltage is 7.2V we are getting only 0.7V instead of 1.58V. We had connected the same battery voltage using the same value resistor to the ADC of the MSP430F5310 microcontroller and here we are getting required voltage with no drop. Could you please explain why the voltage is dropped in imxrt. We see that the voltage drop is decreasing if we reduce the resistor values. We are getting error of almost 0.07V if the resistor values are less than 5K. Also what is the input impedance of the ADC 

[_Leo_]

Hi,

Thank you so much for your interest in our products and for using our community.

Please see the ERR051091 in IMXRT1170CE. There is a weak keeper in IO pad not closed when the pin work as ADC input. So, you must let the input resistor as small as possible.

Hope it helps you. 

Have a nice day!