Analog Considerations for Designing a Potentiostat in a PSoC: Sources of Errors and Compensation Techniques

Designing with a Programmable System on a Chip (PSoC) allows for entire circuit designs to be implemented with a single commercially available chip and eliminates the need to physically assemble electronic components. This is possible as the PSoC incorporates a microcontroller with digital and analog components into a single package. While this design allows for much easier implementation of circuits, there are some drawbacks. In this paper we will demonstrate one of those drawbacks, high routing resistance in parts of the analog mesh that connects the analog parts and external pins. We show how this resistance can cause measurement errors when the PSoC is implemented as a single chip potentiostat. As the internal analog routing resistance is in the kΩ range, measuring currents in the Kॅ range can cause mV errors, leading to lose of voltage control during electrochemical experiments. We also demonstrate a calibration routine to compensate for this voltage error that reduced the error by over 90%.