The HX9031A integrates a capacitance sense AFE used for Specific Absorption Rate (SAR) application. 

The HX9031A supports up to five sensor inputs, with an offset compensation capacitance up to 400pF. The HX9031A has high sensitivity which enables the detection of human body proximity. The portable electronic device can reduce the emission power upon the presence of human body according to the detection result of HX9031A. This will bring significant performance advantages for manufacturers of electronic devices with electro-magnetic radiation sources to meet stringent emission regulations criteria and Specific Absorption Rate (SAR) standards.

The HX9031A can operate from 1.8V single supply, and it outputs data via I2C bus. The I2C serial communication bus port is compatible with 1.65~3.6V host control to report user proximity. Upon proximity detection, the INTN output asserts, enabling the user to either determine the relative proximity distance, or simply obtain an indication of detection.

HX9031A has on-chip calibration logic to account for changes in the ambient environment, such as temperature, humidity. The calibration sequence is performed automatically and at continuous intervals, while the sensors are not touched. This ensures that there are no false detections on the external sensors due to the changing environment.