The 7 series FPGAs XADC is a precision analog measurement system based on a 12-bit analog-to-digital converter (ADC) with an LSB size approximately equal to 250 µV. To achieve the best possible performance and accuracy with all measurements (both on-chip and external), several dedicated pins for the ADC reference and power supply are provided. Care must be taken with the connection of these pins to ensure the best possible performance from the ADC. This chapter outlines the basic design guidelines to consider as part of the requirements for board design.