System Board 5979 MAXREFDES38 : ECT/EPT CURRENT FAULT SENSOR MAXREFDES38 System Board Introduction To realize the vision of a truly smart electricity grid, utilities must find new ways to increase the speed at which they locate, isolate, and fix faults. The electronic current transformer/electronic potential transformer (ECT/EPT), or current fault sensor, fulfills this vision. The ECT/EPT is a low- power sensor that may be placed at many points in the grid thereby increasing the granularity grid health data and fault location. These sensors must be ultra-low power, because they generally receive energy from batteries or nearby fiber optic lines. Although power is readily present in the lines being measured, converting power from the kilovolts in the distribution lines is not feasible. In addition to low-power operation, these sensors must also maintain accuracy and performance, as they provide valuable grid health information during both faults and normal operation. The term ECT/EPT refers to a variety of technologies applied to grid measurement applications. MAXREFDES38 specifically provides the low-power, high-speed, high- accuracy analog front-end designed for the ECT/EPT or current fault sensor application. The MAXREFDES38 features a low-power, 16-bit, high- accuracy, three-channel analog input. Input channels can be configured as 3V single-ended or 6V differential. The P-P P-P MAXREFDES38 design integrates a three-channel analog switch (MAX14531E) a quad precision low-power buffer (MAX44245) a 16-bit fully differential ADC (MAX11901) an ultra-high-precision, 3V voltage reference (MAX6126) a low- noise precision op amp (MAX44241) a STM32L1 microcontroller a supervisory circuit (MAX16058) a 64kB SRAM, a FTDI USB-UART bridge a dual-output step-down DC-DC converter (MAX1775) a switched-capacitor voltage converter (MAX1044) and -3V, 1.8V, 3.3V, 3.38V, 4.5V power rails (MAX1735/MAX8891/MAX8881/MAX8902B/MAX16910). The