Method of and Apparatus for Detecting Open Circuit Conditions at an Input to a Signal Chain and for Detecting Channel Imbalance in a Differential Signal Chain
AssigneeAnalog Devices Global Unlimited Company
InventorsJonathan Ephraim David Hurwitz, Jesus Bonache, Robert Sythes, Eamonn J. Byrne
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Abstract
It is often desirable to distinguish between an open circuit condition and a no signal condition. In both cases an input signal may be absent, but only one of these events represents a failure of the equipment. The present disclosure provides a way to use a difference amplifier to check for open circuit events, without requiring additional circuitry at the input of the amplifier.
Claims20
A method of detecting channel imbalance in a circuit that comprises a differential signal processing circuit, the method comprises modulating a common mode voltage at signal nodes of the signal processing circuit that are distinct from input nodes of the differential signal processing circuit, and monitoring a differential voltage at the signal nodes for changes that are correlated with changes in the common mode voltage at the output.
An apparatus for detecting channel imbalance in a differential signal processing system having a node for controlling a common mode value of a differential output signal, the apparatus comprising a common mode output modulator for modulating a common mode component of differential output signal, and a processor for examining a correlation between the differential output signal and the common mode modulation so as to identify channel imbalance.
An open circuit detector, comprising a first input node, a second input node, a difference amplifier and a signal generator providing a time varying signal for adjusting a common mode output voltage or a common mode input voltage of the amplifier, such that the input current becomes modulated in response to the reference signal, and a circuit for detecting when the common mode gain of the amplifier exceeds a threshold, the reference signal being applied to a node that sets a common mode output voltage of the amplifier or sets a common mode input voltage of the amplifier.
A method of detecting channel imbalance in a circuit that comprises a difference amplifier, the method comprising modulating a common mode voltage at an output of the amplifier and monitoring a differential output voltage of the amplifier to identify changes in the differential output signal that are correlated with changes in the common mode output voltage, and to estimate channel imbalance as a function of a magnitude of the correlation.
Dependencies are inferred from the claim text.