LVDS with idle state

• US 9,362,915 B1
• Filed: 12/12/2014
• Issued: 06/07/2016
• Est. Priority Date: 12/12/2014
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Lubbers, Gilford E., Micielli, Chris J., Phillippe, Jonathan M.
• Primary Examiner(s): Poos, John
• Application Number:
  US14/568,442
• Publication Number:
  US 20160173091A1
• Time in Patent Office: 543 Days
• Field of Search: 327/108, 327/109, 327/110, 327/111, 327/112, 326/30, 326/82, 326/83
• US Class Current: 1/1
• CPC Class Codes: H03K 19/0175 Coupling arrangements; Interface arrangements interface arrangements for digital computers G06F3/00, G06F13/00
• CPC Class Codes: H03K 19/017509 Interface arrangements
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission

Abstract

A low voltage differential signaling generating circuit, which comprises a current source a pair of output nodes for providing a differential signal by virtue of a voltage difference therebetween, first and second differential switch circuitries and a bypass circuitry. The first differential switch circuitry selectively connects the current source to the first output node based on a control signal to cause a current flow from the first output node to the second one. The second differential switch circuitry selectively connects the current source to the second output node based on the control signal to cause a current flow from the second output node to the first one. The bypass circuitry is arranged in parallel to the first and second differential switch circuitries and is selectively switched based on an idle mode signal to prevent a current between the output nodes.

Claims

1. A low voltage differential signaling generating circuit, comprising:

at least one current source,

a pair of output nodes for providing a differential signal by virtue of a voltage difference between the pair of output nodes;

a first differential switch circuitry configured to be switched based on a control signal to selectively connect the current source to a first one of the pair of output nodes to cause a current flow from the first output note to the second output node;

a second differential switch circuitry configured to be switched based on the control signal to selectively connect the current source to the second output node to cause a current flow from the second output note to the first output node; and

a bypass circuitry arranged in parallel to the first and second differential switch circuitries and configured to be selectively switched based on an idle mode signal to prevent a current between the pair of output nodes;

a feedback circuitry configured to generate a control signal for adjusting the current flow supplied by the at least one current source on the basis of a voltage at the bypass circuitry,

wherein the at least one current source is configured to adjust the current flow supplied thereof in accordance with the control signal.

2. The circuit according to claim 1,

wherein the feedback circuitry is further configured to generate the control signal for adjusting the current flow supplied by the at least one current source on the basis of an average voltage of voltages at the first and second output nodes.

3. The circuit according to claim 2, comprising:

a first current source, which is arranged upstream the circuitries; and

a second current source, which is arranged downstream the circuitries,

wherein the first and the second current source is configured to adjust the current flow supplied thereof in accordance with the control signal.

4. The circuit according to claim 2,

wherein the pair of output nodes are coupled resistively to each other and the average voltage of the voltages at the first and second output nodes is tapped at the resistive coupling thereof.

5. The circuit according to 1,

wherein the first and the second differential switch circuitries have a common supply input node which is connected to the current source, and a common supply output node, and comprise the pair of output nodes,

wherein the first differential switch circuitry further comprises a first switching element and a second switching element, wherein the first switching element is arranged upstream the pair of output nodes, wherein the second switching element is arranged downstream the pair of output nodes,

wherein the second differential switch circuitry further comprises a third switching element and a fourth switching element, wherein the third switching element is arranged upstream the pair of output nodes, wherein the fourth switching element (318) is arranged downstream the pair of output nodes.

6. The circuit according to claim 5,

wherein when the first differential switch circuitry switches to connect the current source to the first output node, the first and second switching elements are operated in conductive state and the third and fourth switching elements are operated in nonconductive state,

wherein when the second differential switch circuitry switches to connect the current source to the second output node, the third and fourth switching elements are operated in conductive (closed) state and the first and second switching elements are operated in nonconductive (open) state.

7. The circuit according to claim 6,

wherein the bypass circuitry is interconnected between the common supply input node and the common supply output node,

wherein the bypass circuitry further comprises at least one switching element.

8. The circuit according to claim 7,

wherein when one of the first and the second differential switch circuitries is switched to connect the current source to one of the first and the second output nodes, the at least one switching element is operated in nonconductive state,

when the bypass circuitry is switched to prevent a current between the pair of output nodes, the at least one switching element is operated in conductive state and the first to fourth switching elements of the differential switch circuitries are operated in nonconductive state.

9. The circuit according to claim 7,

wherein the pair of output nodes are resistively coupled to each other,

wherein the resistive coupling and the bypass circuitry have a common connection point.

10. The circuit according to claim 9, wherein

the resistive coupling of the pair of output nodes comprises two switching elements, one of which is arranged upstream and the other one of which is arranged downstream to the common connection point.

11. The circuit according to claim 10, wherein one or more of the switching elements are transistors,

wherein each of the transistors is one of a pMOS transistor or an nMOS transistor.

12. The circuit according to claim 1,

wherein the control signal is a complementary control signal.

13. The circuit according to claim 1,

wherein the first differential switch circuitry and the second differential switch circuitry form an H-bridge circuitry.

14. The circuit according to claim 1,

wherein the low voltage differential signaling generating circuit is provided to generate differential communication signals for signal communication on a communication line having at least two wires,

wherein a receiver is configured to receive differential communication signals on the communication line when the low voltage differential signaling generating circuit is in idle mode.

15. An integrated circuit, comprising:

at least one current source and a low voltage differential signaling generating circuit,

wherein the low voltage differential signaling generating circuit further comprises;

a pair of output nodes for providing a differential signal by virtue of a voltage difference between the pair of output nodes;

a first differential switch circuitry configured to be switched based on a control signal to selectively connect the current source to a first one of the pair of output nodes to cause a current flow from the first output note to the second output node;

a second differential switch circuitry configured to be switched based on the control signal to selectively connect the current source to the second output node to cause a current flow from the second output note to the first output node;

a bypass circuitry arranged in parallel to the first and second differential switch circuitries and configured to be selectively switched based on an idle mode signal to prevent a current between the pair of output nodes;

a signal transmitter comprising the low voltage differential signaling generating circuit (202) for transmitting differential communication signals on a shared communication medium; and

a signal receiver for receiving differential communication signals communicated on the shared communication medium, wherein the integrated circuit is capable of bi-directional data communication on the basis of differential communication signals on the shared communication medium having at least two wires.

16. The integrated circuit according claim 15, wherein

the signal receiver is configured to be selectively operated when the low voltage differential signaling generating circuit is in the idle mode.

17. Method of operating a low voltage differential signaling generating circuit, comprising:

providing at least one current source,

providing a pair of output nodes for outputting a differential output signal by virtue of a voltage difference between the pair of output nodes;

based on a control signal, selectively connecting the current source to a first one of the pair of output nodes through a first differential switch circuitries to cause a current flowing from the first output note to the second output node;

based on the control signal, selectively connecting the current source to the second output node through a second differential switch circuitries to cause a current flowing from the second output note to the first output node; and

based on an idle mode signal, selectively switching a bypass circuitry arranged in parallel to the first and second differential switch circuitries to prevent a current flowing between the pair of output nodes;

generating a control signal for adjusting the current flow supplied by the at least one current source on the basis of a voltage at the bypass circuitry in feedback circuitry,

wherein the at least one current source is configured to adjust the current flow supplied thereof in accordance with the control signal.