Tool/software:
As We are using this Part in Our Design, and Driving The I/0 in ADC Mode ,
So , please Confirm can we Set Open Circuit Value for ADC .
As of Now in Open Circuit it is Showing The Maximum Value ie 1023 with i/0 is Open .
So It is Difficult to identify the circuit is close or Open.
Please Suggest is It possible To configure The ADC Open Circuit Values in IC.
Regards
Satish Kumar
Hi Satish,
An Open INx pin will always read High due to the leakage current flowing in the MUX circuit between the VS supply pin and the INx pin.
There is a small amount of current needed to active the gates of FETs in the MUX and connect the INx pin to the ADC or Comparator for measurement. This current flows from the VS supply pin to the INx pin where it is usually absorbed by the external switch or filter capacitor.
This is specified in the datasheet under the 0mA condition which has the current source and current sink circuits disabled which would otherwise mask or absorb this leakage current.
It is not possible to configure Open Circuit values. When the INx pin is Open, there is no path for this leakage current to flow and the ADc will read a High value. However, the ESD filter Capacitor that should be on the INx pin will also act as a decoupling capacitor and absorb this leakage current. Therefore, having a capacitor of 15nF or greater on each INx pin is recommended.
Regards,
Jonathan
