Low voltage differential signaling (LVDS) circuitry and method for dynamically controlling common mode voltage at input
AssigneeNational Semiconductor Corporation
InventorsArlo J. Aude, Soumya Chandramouli
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Abstract
Low voltage differential signaling (LVDS) circuitry and method for dynamically controlling the common mode voltage at the input of an LVDS receiver. The common mode voltage of the incoming LVDS signal is monitored. The common mode voltage at the input of the LVDS receiver is clamped at a clamp voltage when the common mode voltage of the incoming LVDS signal is less than a predetermined voltage, and allowed to track it otherwise.
Claims19
An apparatus including low voltage differential signaling (LVDS) circuitry capable of adaptively maintaining a minimum common mode input voltage, comprising:
- LVDS amplifier circuitry including input circuitry and output circuitry, and responsive to a LVDS input signal that includes a signal voltage and an input common mode voltage by providing a corresponding LVDS output signal and a voltage related to said input common mode voltage;
- voltage sensing circuitry coupled to said LVDS amplifier circuitry and responsive to said voltage related to said common mode voltage by providing at least one control signal;
- and
- voltage clamping circuitry coupled to said voltage sensing circuitry and said LVDS amplifier circuitry and responsive to said voltage sensing circuitry and said LVDS amplifier circuitry and responsive to said at least one control signal by
- clamping first and second common mode voltages within said input circuitry at a clamp voltage when said input common mode voltage is less than a predetermined reference voltage, and
- allowing said first and second common mode voltages within said input circuitry to track said input common mode voltage otherwise.
A system for low voltage differential signaling (LVDS) capable of adaptively maintaining a minimum common mode input voltage, comprising:
- a signaling interface coupled to a data communication link, and configured for at least one of receiving and transmitting LVDS signals;
- an LVDS signaling circuit coupled to the signaling interface, and including
- LVDS amplifier circuitry including input circuitry and output circuitry;
- and responsive to a LVDS input signal that includes a signal voltage and an input common mode voltage by providing a corresponding LVDS output signal and a voltage related to said input common mode voltage,
- voltage sensing circuitry coupled to said LVDS amplifier circuitry and responsive to said voltage related to said common mode voltage by providing at least one control signal, and
- voltage clamping circuitry coupled to said voltage sensing circuitry and said LVDS amplifier circuitry and responsive to said at least one control signal by
- clamping first and second common mode voltages within said input circuitry at a clamp voltage when said input common mode voltage is less than a predetermined reference voltage, and
- allowing said first and second common mode voltages within said input circuitry to track said input common mode voltage otherwise.
A method of adaptively maintaining a minimum common mode input voltage for use in connection with low voltage differential signaling (LVDS) circuitry, comprising:
- responding to a LVDS input signal that includes a signal voltage and an input common mode voltage by providing a corresponding LVDS output signal and a voltage related to said input common mode voltage;
- responding to said voltage related to said input common mode voltage by providing at least one control signal;
- and
- responding to said at least one control signal by
- clamping first and second common mode voltages within said input circuitry at a clamp voltage when said input common mode voltage is less than a predetermined reference voltage;
- and
- allowing said first and second common mode voltages within said input circuitry to track said input common mode voltage otherwise.
Dependencies are inferred from the claim text.