Differential input receiver circuit testing with a loopback circuit

An integrated circuit device comprising:

• a digital controller configured to provide a digital test sequence and receive a digital response sequence in response to the digital test sequence;
• a dummy transmitter configured to convert the digital test sequence to test differential signals, wherein the test differential signals are based on a tunable common mode voltage that varies incrementally over time over a range of common mode voltages;
• and
• a receiver circuit configured to convert the test differential signals from the dummy transmitter into the digital response sequence, wherein the range of common mode voltages includes a range of common mode voltages potentially used in the receiver circuit.

A method of testing a low voltage differential signaling (LVDS) receiver having a receiver circuit and a transmitter circuit, comprising:

• during a test mode of operation:
• generating test differential signals, by the transmitter circuit, from an input digital test sequence based on a tunable common mode voltage that varies incrementally over time over a range of common mode voltage values potentially used in a receiver circuit;
• providing the test differential signals to the receiver circuit;
• generating, by the receiver circuit, a digital response sequence in response to the test differential signals to determine whether the digital response sequence matches the digital test sequence;
• and
• when the digital response sequence from the receiver matches the digital test sequence, generating the test differential signals, by the transmitter circuit, using a next common mode voltage value for the tunable common mode voltage.