1 Introduction

High performance power supplies for server applications incorporate an output current monitoring pin which provides a scaled down representation of the output current. This current monitoring function provides valuable information about the real-time output current on different voltage buses. The current monitor pins from multiple power supplies can also be joined together to measure the total output current on multiple buses.

Current transmitter products, such as the XTR200, are useful building blocks for performing the current monitor function. These devices convert an input voltage to an output current with a transfer function specified by a single external resistor. The XTR200 also integrates the output transistor, protection circuitry, and diagnostic capabilities in an extremely small 2mm × 3mm WSON package that is designed for space-constrained power supply and motherboard PCBs.

The Open Compute Project (OCP), which is a collaboration between multiple companies, has defined a standard for power supplies called the Modular Hardware System – Common Redundant Power Supply (M-CRPS) Base Specification [1]. The standards document clearly outlines several requirements for current monitoring outputs which allows interoperability across hardware from multiple manufacturers. The requirements for M-CRPS current monitoring outputs are outlined in Table 1-1: