Micrel, Incorporated

Vincent Stueve

Thomas S Wong

A signal detection circuit for an Ethernet physical layer transceiver (PHY) device includes a first capacitor AC coupling a signal on the first receive terminal of the Ethernet PHY device to a first node; a second capacitor AC coupling a signal on the second receive terminal to a second node; re-biasing resistors for re-biasing the AC-coupled signals on the first and second nodes; first and second gain stages for amplifying the AC coupled signals; and a peak detect circuit. The peak detect circuit includes first and second diodes receiving the amplified signals from the gain stages to charge a peak detect capacitor. The signal detection circuit includes a comparator for comparing the voltage on the peak detect capacitor to a reference voltage and providing an output signal being indicative of the presence or absence of a signal on the first and second receive terminals of the Ethernet PHY device.

Low current method for detecting presence of Ethernet signals

A digital signal detector detects digital signals by only sensing the rising and falling edges of a received digital signal and latches the logic state between the detected edges. Such edges contain very high frequencies that are much higher than the fundamental frequency of the digital signal train. A small high pass filter filters out at least the DC component and the fundamental frequency of the received digital signal. A filtered edge appears as a spike that goes either positive or negative depending on whether the edge is a rising or falling edge. A memory element, such as comprising an RS flip flop, is triggered by the positive and negative spikes. A positive spike triggers the flip flop to output a logical one, and a negative spike triggers the latch to output a logical zero. In this way, the digital signal is recreated without the original digital signal itself being required to pass through the high pass filter.

Growing community of inventors

Round Rock, TX, United States of America

Vincent Stueve