Low-voltage differential signal driver for high-speed digital transmission

• US 7,427,878 B2
• Filed: 06/01/2006
• Issued: 09/23/2008
• Est. Priority Date: 06/01/2006
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Jiang, Jian Hong, Koyanagi, Yoichi
• Primary Examiner(s): Barnie; Rexford
• Assistant Examiner(s): Tabler; Matthew C
• Application Number:
  US11/421,522
• Publication Number:
  US 20070279098A1
• Time in Patent Office: 845 Days
• Field of Search: 326 62- 92, 326 9- 15, 326 21- 34, 326 59- 60
• 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:

a high speed component comprising a first set of two or more programmable fingers;

a low speed component comprising a second set of two or more programmable fingers;

a plurality of pre-drivers, each pre-driver associated with a programmable finger of either the high speed component or the low speed component and operable to enable or disable the associated programmable finger, an enabled programmable finger driving a signal and contributing to capacitive loading of the driver, and a disabled programmable finger not driving the signal and not contributing to the capacitive loading of the driver;

wherein the drivers are configured to enable the programmable fingers of the high speed component to drive the signal at a high speed;

wherein the drivers are configured to enable the programmable fingers of the high speed component and the programmable fingers of the low speed component to drive the signal at a low speed to contribute to the capacitive loading of the driver.

2. The driver of claim 1, wherein each pre-driver comprises pre-driver logic.

3. The driver of claim 1, wherein the programmable finger 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 two of the programmable fingers are enabled to facilitate the transmission of the signal at the 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 the five programmable fingers are enabled to facilitate the transmission of a signal at the 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 a first set of two or more programmable fingers of a high speed component;

selectively enabling a second set of two or more programmable fingers of a low speed component;

wherein a programmable finger of either the high speed component or the low speed component is operable to drive a signal, an enabled programmable finger driving the signal and contributing to capacitive loading of a driver, and a disabled programmable finger not driving the signal and not contributing to the capacitive loading of the driver;

wherein selectively enabling a first set of two or more programmable fingers comprises enabling the programmable fingers of the high speed component to drive the signal at a high speed;

wherein selectively enabling a second set of two or more programmable fingers comprises enabling the programmable fingers of the high speed component and the programmable fingers of the low speed component to drive the signal at a low speed to contribute to the capacitive loading of the driver.

9. The method of claim 8, wherein selectively enabling either the first set of two or more programmable fingers or the second set of two or more programmable fingers comprises receiving a signal at the driver.

10. The method of claim 8, wherein selectively enabling either the first set of two or more programmable fingers or the second set of two 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 the first set of two or more programmable fingers comprises:

enabling two programmable fingers to facilitate the transmission of the signal at the 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 the first set of two or more programmable fingers and the second set of two or more programmable fingers comprises:

enabling five programmable fingers to facilitate the transmission of the signal at the 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;

means for selectively enabling a first set of two or more programmable fingers of a high speed component;

means for selectively enabling a second set of two or more programmable fingers of a low speed component;

wherein an enabled driving means drives the signal and contributes to the capacitive loading of driving means, and a disabled driving means does not drive the signal and does not contribute to the capacitive loading of the driving means;

wherein means for selectively enabling a first set of two or more programmable fingers comprises means for enabling the programmable fingers of the high speed component to drive the signal at a high speed;

wherein means for selectively enabling a second set of two or more programmable fingers comprises means for enabling the programmable fingers of the high speed component and the programmable fingers of the low speed component to drive the signal at a low speed to contribute to the capacitive loading of the driver.

16. The system of claim 15, further comprising means for receiving a signal at 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 the 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 the low speed; and

means for having a high output voltage swing.