Loop current monitor circuitry and method for a communication system

摘要

Monitor circuitry is disclosed that produces a loop current monitor signal indicative of the DC loop current passing through DC holding circuitry, which may be part of phone line side circuitry that may be connected to phone lines. This loop current monitor signal may be digitized and then communicated across an isolation barrier to powered side circuitry as digital information representative of the DC loop current levels in the phone lines. Example embodiments for the monitor circuitry are also disclosed, such as a MOS transistor, for which the monitor signal is the drain current of the MOS transistor, and an external resistor, for which the monitor signal is a voltage associated with the external resistor.