EMI robust design of sensor-frontends

Sensors are the first element in a signal chain and in order to fulfill their function they often have to be placed in close proximity to the measured object and substance. Consequently, a certain amount of wiring is required that is vulnerable to electromagnetic interferences. This is particularly true, when sensors are used that use the electromagnetic field for powering and data-transfer. In this case, the EMI robustness is of fundamental importance since it limits the accuracy of the measurement and has to be considered an integral part of the design process.

The focus will be on potentiostats, which are used as a front-end for electrochemical sensors, which are powered and read out using near-field communication (NFC). The design of these circuits comprises a number of different challenges. The energy is harvested from the field which limits the quality of the on-chip power supply and the amount of power that is available to operate the circuit.

A number of different topologies exist to realize the potentiostat. The focus will be on three-electrode configurations, where the voltage between a reference electrode (RE) and the working electrode (WE) is controlled using the control electrode (CE). The injected current has to be measured.
Different topologies will be presented and compared regarding their applicability for the required measurements. Methods to process the output signal under the presence of interferers will be discussed.