Apparatus and method for detecting loss of high-speed signal

A method of detecting loss of signal on a pair of conductors adapted to carry a pair of differential signals, comprising:

• generating voltages on a pair of signal lines by buffering levels on a pair of conductors;
• detecting a common mode level of said voltages on said pair of signal lines;
• generating a threshold level referenced to said detected common mode level;
• generating a short-term averaged signal level by operating a first charge pump with said voltages on said pair of signal lines;
• generating a reference level averaged over a longer term than said signal level by operating a second charge pump with said threshold level and said common mode level;
• comparing said signal level to said reference level to determine if a signal is present on said pair of signal lines, said comparing determining that a signal is not present when said signal level is less than or equal to said reference level.

An apparatus for detecting loss of a signal on a pair of signal lines adapted to carry a pair of differential signals, comprising:

• a level generator operable to detect a common mode level of voltages on a pair of signal lines and
• operable to generate a threshold level referenced to said detected common mode level;
• a first charge pump operable by said voltages on said pair of signal lines to generate a short-term averaged signal level;
• a second charge pump operable by said threshold level and said common mode level to generate a reference level averaged over a longer term than said signal level;
• and
• a comparator operable to compare said signal level to said reference level to determine if a signal is present on said pair of signal lines.

An apparatus for detecting loss of a signal on a pair of signal lines adapted to carry a pair of differential signals, comprising:

• level generating means for detecting a common mode level of a pair of voltages on a pair of signal lines and
• for generating a threshold level referenced to said detected common mode level;
• means for generating a short-term averaged signal level with said voltages on said pair of signal lines;
• means for generating a reference level averaged over a longer term than said signal level;
• and
• means for comparing said signal level to said reference level to determine if a signal is present on said pair of signal lines.