LOW-VOLTAGE DIFFERENTIAL SIGNAL DRIVER FOR HIGH-SPEED DIGITAL TRANSMISSION

• US 20070279098A1
• Filed: 06/01/2006
• Published: 12/06/2007
• Est. Priority Date: 06/01/2006
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Jiang, Jian Hong, Koyanagi, Yoichi
• Granted Patent: US 7,427,878 B2
• Time in Patent Office: Days
• US Class Current: 326/83
• CPC Class Codes: H03K 19/018528 with at least one differential stage

Abstract

A low-voltage differential signal (LVDS) driver includes at least two programmable fingers operable to drive a signal and at least two pre-drivers. Each pre-driver is associated with one or more of the programmable fingers and is operable to enable or disable the associated one or more programmable fingers. An enabled programmable finger drives the signal and contributes to the capacitive loading of the driver, and a disabled programmable finger does not drive the signal and does not contribute to the capacitive loading of the driver.

Claims

1. A low-voltage differential signal (LVDS) driver, comprising:

at least two programmable fingers operable to drive a signal; and

at least two pre-drivers, each pre-driver associated with one programmable finger and operable to enable or disable the associated programmable finger, an enabled programmable finger driving the signal and contributing to the capacitive loading of the driver, and a disabled programmable finger not driving the signal and not contributing to the capacitive loading of the driver.

2. The driver of claim 1, wherein the at least two pre-drivers each comprises pre-driver logic.

3. The driver of claim 1, wherein the at least two programmable fingers each comprises a plurality of transistors, the plurality of transistors comprising a plurality of p-channel metal-oxide field effect transistors and a plurality of n-channel metal-oxide field effect transistors.

4. The driver of claim 1, comprising five programmable fingers and wherein only two of the programmable fingers are enabled to facilitate the transmission of the signal at a high speed, wherein the driver has a low output voltage swing.

5. The driver of claim 4, wherein the high speed transmission is greater than or equal to approximately ten Gigabits per second and the low output voltage swing of a differential circuit is less than or equal to approximately 600 mV and the low output voltage swing of a single-end circuit is less than or equal to approximately 300 mV.

6. The driver of claim 1, comprising five programmable fingers and wherein all five of the programmable fingers are enabled to facilitate the transmission of a signal at a low speed, wherein the driver has a high output voltage swing.

7. The driver of claim 6, wherein the low speed transmission is less than or equal to approximately three Gigabits per second and the high output voltage swing of a differential circuit is greater than or equal to approximately 1200 mV and the high output voltage swing of a single-end circuit is greater than or equal to approximately 600 mV.

8. A method for driving a low-voltage differential signal (LVDS), comprising selectively enabling one or more programmable fingers of an LVDS driver, each programmable finger operable to drive a signal, an enabled programmable finger driving the signal and contributing to the capacitive loading of the driver, and a disabled programmable finger not driving the signal and not contributing to the capacitive loading of the driver.

9. The method of claim 8, wherein selectively enabling one or more programmable fingers comprises receiving a signal at PD of the driver.

10. The method of claim 8, wherein selectively enabling one or more programmable fingers comprises receiving an input having a logic value of zero or one.

11. The method of claim 8, wherein selectively enabling one or more programmable fingers comprises:

enabling two programmable fingers to facilitate the transmission of the signal at a high speed; and

having a low output voltage swing.

12. The method of claim 11, wherein the high speed transmission is greater than or equal to approximately ten Gigabits per second and the low output voltage swing of a differential circuit is less than or equal to approximately 600 mV and the low output voltage swing of a single-end circuit is less than or equal to approximately 300 mV.

13. The method of claim 8, wherein selectively enabling one or more programmable fingers comprises:

enabling five programmable fingers to facilitate the transmission of the signal at a low speed; and

having a high output voltage swing.

14. The method of claim 13, wherein the low speed transmission is less than or equal to approximately three Gigabits per second and the high output voltage swing of a differential circuit is greater than or equal to approximately 1200 mV and the high output voltage swing of a single-end circuit is greater than or equal to approximately 600 mV.

15. A system for driving a low-voltage differential signal (LVDS), comprising:

means for driving a signal; and

means for selectively enabling one or more driving means of an LVDS driver, an enabled driving means driving the signal and contributing to the capacitive loading of the driver, and a disabled driving means not driving the signal and not contributing to the capacitive loading of the driver.

16. The system of claim 15, further comprising means for receiving a signal at PD of the driver.

17. The system of claim 15, further comprising means for receiving an input having a logic value of zero or one.

18. The system of claim 15, further comprising:

means for driving the signal at a high speed; and

means for having a low output voltage swing.

19. The system of claim 15, further comprising:

means for driving the signal at a low speed; and

means for having a high output voltage swing.