Patent ID: 7550980
Filing Date: 2009-06-23
Classification: H04L

Abstract:
1. Apparatus associated with power sourcing equipment having an output port, the apparatus for determining whether a load in a powered device that is coupled to the power sourcing equipment via a conductive cable via the output port has an acceptable resistance, the apparatus comprising: at least one current source for generating first and second test currents during successive first and second time periods, wherein the second test current is different in magnitude from the first test current; and control logic operative to couple the first and second test currents to the cable during the first and second successive time periods to produce successive first and second output port voltages based at least in part upon respective first and second voltage drops across the load produced by the first and second test currents when the first and second test currents are coupled to the load through the cable; a converter operative to generate first recharge and discharge currents responsive to the first and second output port voltages respectively, the magnitude of the first recharge and first discharge currents being proportional to the first and second output voltages respectively by a proportionality factor; a capacitor, the control logic further operative to: at least one comparator operative in response to the control logic to determine whether the load has a resistance less than a predetermined minimum acceptable resistance by comparing the first final voltage on the capacitor against a first predetermined first threshold voltage.