Use of differential pair as single-ended data paths to transport low speed data

• US 20080117994A1
• Filed: 11/17/2006
• Published: 05/22/2008
• Est. Priority Date: 11/17/2006
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Shetty, Naresh B.
• Granted Patent: US 7,953,162 B2
• Time in Patent Office: Days
• US Class Current: 375/257
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission
• CPC Class Codes: H04L 25/45 using electronic distributors
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

Provided herein are systems and methods for transmitting signals across a pair of wires. In accordance with specific embodiments, a differential signal is transmitted across the pair of wires during one period of time, and two single-ended signals are transmitted across the same pair of wires during another period of time. Low voltage differential signaling (LVDS) can be used to transmit the differential signal across the pair of wires. In contrast, non-differential signaling can be used to transfer the two singled-ended signals across the same pair of wires.

Claims

1. A method for transmitting signals across a pair of wires, comprising:

(a) transmitting a differential signal across the pair of wires during a period of time; and

(b) transmitting two single-ended signals across the same pair of wires during another period of time.

2. The method of claim 1, wherein:

step (a) includes using low voltage differential signaling (LVDS) to transmit the differential signal across the pair of wires; and

step (b) includes using non-differential signaling to transfer the two singled-ended signals across the same pair of wires.

3. The method of claim 1, wherein the pair of wires comprises a twisted pair.

4. The method of claim 1, wherein the pair of wires comprises a pair of conductive traces.

5. The method of claim 1, wherein:

step (a) is performed when a device is in a first mode; and

step (b) is performed when a device is in a second mode.

6. the method of claim 5, wherein:

the first mode is an active mode; and

the second mode is a sleep or standby mode.

7. The method of claim 5, wherein the second mode is a reduce power mode as compared to the first mode.

8. A method, for reducing power consumption in a battery powered mobile device that has a first mode and a second mode, the method comprising:

(a) using low voltage differential signaling (LVDS) to transfer both a first type of information and a second type of information across a pair of wires, when the device is in the first mode; and

(b) using non-differential signaling to transfer the second type of information, but not the first type of information, across the same pair of wires, when the device is in the second mode.

9. The method of claim 8, wherein:

step (a) includes using the pair of wires as a single differential pair, when the device is in the first mode; and

step (b) includes using the pair of wires as two separate serial lines, when the device is in the second mode.

10. The method of claim 8, wherein:

the first mode is an active mode; and

the second mode is a sleep or standby mode.

11. The method of claim 8, wherein the second mode is a reduce power mode as compared to the first mode.

12. The method of claim 8, wherein:

the first type of information includes data that is to be transferred at a first speed; and

the second type of information includes data that is to be transferred at a lower speed than the first speed.

13. The method of claim 8, wherein:

the first type of information includes a video signal, at least one corresponding control signal, and a corresponding first clock signal; and

the second type of information includes a low speed control data signal and a corresponding second clock signal that is slower than the first clock signal.

14. A system, comprising:

a transmitter including a pair of outputs; and

a receiver including a pair of inputs;

wherein the pair of outputs of the transmitter are configured to be connected, by a pair of wires, to the two inputs of the receiver;

wherein the transmitter, when in a first mode, outputs a differential signal at the two outputs to transmit across the two wires to the two inputs of the receiver; and

wherein the transmitter, when in a second mode, outputs two single-ended signals, one at each of the two outputs, to transmit across the same two wires to the two inputs of the receiver.

15. The system of claim 14, wherein:

the receiver can also be in the first mode and the second mode;

the receiver treats signals received at its two inputs as a differential signal, when the receiver is in the first mode; and

the receiver treats signals received at its two inputs as two single-ended signals when the receiver is in the second mode.

16. The system of claim 14, wherein:

the first mode is an active mode; and

the second mode is a sleep or standby mode.

17. The system of claim 14, wherein the second mode is a reduce power mode as compared to the first mode.

18. The system of claim 14, wherein the transmitter includes a pair of switches that enable I2C data and clock signals to be transmitted either as an embedded portion of a differential signal across the pair of wires, or as two separate single-ended signals across the same pair of wires.

19. The system of claim 14, wherein:

the transmitter includes a serializer and an output stage that produces a differential signal based on an output of the serializer; and

the receiver includes an input stage that produces a single-ended signal based on the differential signal received at the two inputs of the receiver, and a deserializer that receives an output of the input stage.

20. A system for transmitting signals across a pair of wires, comprising:

means for transmitting a differential signal across the pair of wires during a period of time; and

means for transmitting two single-ended signals across the same pair of wires during another period of time.