Transient signal detector
AssigneeNational Semiconductor Corporation
InventorDuncan James Bremner
Life of this patent
Estimating the term…
Abstract
A transient signal detector for monitoring a signal line and generating a control signal which indicates when the magnitude of a differential signal on the line exceeds either a positive or negative threshold value. The threshold value is defined by a single current, thereby allowing for a single, simple adjustment of such threshold in both the positive and negative directions.
Claims9
An apparatus including a transient signal detector for monitoring a signal and indicating when such signal has a magnitude which extends in either direction outside of a range defined by positive and negative threshold values, comprising:
- a differential buffer circuit that following reception of a differential signal selectively provides first and second currents, wherein
- said first and second currents are mutually exclusive,
- said first current is provided when said differential signal has a first polarity and a magnitude which exceeds a first threshold value,
- said second current is provided when said differential signal has a second polarity and a magnitude which exceeds a second threshold value, and
- each of said first and second currents is substantially zero when said differential signal has said first polarity and said differential signal magnitude is less than said first threshold value and when said differential signal has said second polarity and said differential signal magnitude is less than said second threshold value;
- an output circuit that selectively conveys a third current following reception thereof;
- and
- a current sinking circuit that is coupled to said differential buffer circuit and said output circuit and that
- sinks said first current via a common current path when said differential signal has said first polarity and said differential signal magnitude exceeds said first threshold value,
- sinks said second current via said common current path when said differential signal has said second polarity and said differential signal magnitude exceeds said second threshold value,
- sinks said third current via said common current path when said differential signal has said first polarity and said differential signal magnitude is less than said first threshold value, and
- sinks said third current via said common current path when said differential signal has said second polarity and said differential signal magnitude is less than said second threshold value,
- whereby one of said first, second and third currents exclusively is sunk by said current sinking circuit via said common current path.
A method of monitoring a signal and indicating when such signal has a magnitude which extends in either direction outside of a range defined by positive and negative threshold values, said method comprising the steps of:
- receiving a differential signal and in response thereto
- generating a first internal current with a first nonzero magnitude when said differential signal has a first polarity and a magnitude which exceeds a first threshold value,
- generating a second internal current with a second nonzero magnitude when said differential signal has a second polarity and a magnitude which exceeds a second threshold value, and
- maintaining said first and second internal currents at first and second substantially zero magnitudes when said differential signal has said first polarity and said differential signal magnitude is less than said first threshold value and when said differential signal has said second polarity and said differential signal magnitude is less than said second threshold value,
- wherein said first and second internal currents are mutually exclusive;
- sinking said first internal current via a common current path when said differential signal has said first polarity and said differential signal magnitude exceeds said first threshold value;
- sinking said second internal current via said common current path when said differential signal has said second polarity and said differential signal magnitude exceeds said second threshold value;
- sinking an external current via said common current path when said differential signal has said first polarity and said differential signal magnitude is less than said first threshold value;
- and
- sinking said external current via said common current path when said differential signal has said second polarity and said differential signal magnitude is less than said second threshold value;
- whereby one of said first and second internal currents and said external current exclusively is sunk at one time via said common current path.
Dependencies are inferred from the claim text.