Voltage swing detection circuit for hot plug event or device detection via a differential link

A system, including:

• a transmitter;
• and
• a differential link, coupled to the transmitter and capable of being coupled to a device,
• wherein the transmitter includes a device detection circuit, said device detection circuit comprising:
• a first branch having a first node configured to be coupled to one conductor of the link, and including a first switch;
• a second branch having a second node configured to be coupled to another conductor of the link, and including a second switch;
• a current source, coupled to the first branch and the second branch, and operable to cause current to flow through either one of the first branch and the second branch, or to be shared by both the first branch and the second branch, depending on the state of the first switch and the second switch;
• switch control circuitry, coupled to the first switch and the second switch, and operable in a device detection mode to sequence the first switch and the second switch between a first state and a second state, wherein the first switch is open and the second switch is closed in the first state, and the first switch is closed and the second switch is open in the second state;
• and
• a voltage swing detector, coupled to the first node and the second node, and operable in the device detection mode to detect the voltage between the first node and the second node and to assert an output signal,
• wherein, when the first node and the second node are coupled to the differential link, the output signal is indicative of whether the device is coupled to the differential link.

A transmitter, including:

• a voltage swing detector;
• and
• differential signal transmission circuitry, wherein the differential signal transmission circuitry comprises:
• a first branch including a first node and a first switch;
• a second branch including a second node and a second switch, wherein each of the first node and the second node is configured to be coupled to a differential link;
• a current source, coupled to the first branch and the second branch, and operable to cause current to flow through either one of the first branch and the second branch, or to be shared by both the first branch and the second branch, depending on the state of the first switch and the second switch;
• and
• switch control circuitry coupled to the first switch and the second switch, and operable in a device detection mode to sequence the first switch and the second switch between a first state and a second state, wherein the first switch is open and the second switch is closed in the first state, and the first switch is closed and the second switch is open in the second state,
• wherein the voltage swing detector is coupled to the first node and the second node and operable in the device detection mode to detect the voltage between the first node and the second node and to assert an output signal, and wherein when the first node and the second node are coupled to the differential link, the output signal is indicative of whether a receiver is coupled to the differential link.