Low voltage differential signal driver circuit and method

• US 6,900,663 B1
• Filed: 11/04/2002
• Issued: 05/31/2005
• Est. Priority Date: 11/04/2002
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Roper, Weston, Feng, Xiaoxin
• Primary Examiner(s): CHO, JAMES HYONCHOL
• Application Number:
  US10/288,003
• Time in Patent Office: 939 Days
• Field of Search: 326 82- 83, 326 86- 87, 327108-109, 330258-261
• US Class Current: 326/83
• CPC Class Codes: H04L 25/028 Arrangements specific to the transmitter end

Abstract

Embodiments of the present invention relate to a low voltage differential signal driver (LVDS) circuit which comprises a current source, logic controlled switches for controlling the driver'"'"'s output, an electronic load circuit coupled across the circuit, and a common-mode resistor feedback circuit coupled across the circuit, in parallel with the RC load, for tuning the driver'"'"'s impedance. The driver is enabled to operate without op-amps and achieves optimum performance at 1.8 v supply voltages.

Claims

1. A system for driving a low voltage differential signal comprising:

a current source;

a driver circuit coupled to said current source and controlled by logical switches, wherein said driver circuit comprises a common-mode resistor feedback circuit for reducing an output impedance of said driver circuit during transitions in said low voltage differential signal;

a current mirror coupled to said driver circuit and controlled by a feedback voltage of said common mode resistor feedback circuit; and

a bias voltage source coupled to said current mirror and enabled to control said current mirror.

2. The system for driving a low voltage differential signal described in claim 1, wherein said driver circuit further comprises a capacitive load.

3. The system for driving a low voltage differential signal described in claim 1, wherein said driver circuit further comprises a resistive load.

4. The system for driving a low voltage differential signal described in claim 1, wherein said current source is controlled by said feedback voltage of said common-mode resistor feedback circuit.

5. The system for driving a low voltage differential signal described in claim 1, wherein said common-mode resistor feedback circuit enables tuning said output impedance of said driver circuit.

6. The system for driving a low voltage differential signal described in claim 1, wherein said driver circuit is enabled to operate in a single pole mode.

7. The system for driving a low voltage differential signal described in claim 1, wherein said driver circuit further comprises:

a resistive load; and

a parasitic capacitance of said system.

8. A low voltage differential signal driver circuit, comprising:

an electronic load circuit coupled to said current source, wherein an output signal is generated as a function of a direction of a current flowing through said electronic load circuit;

logic controlled switches coupled to said current source, for selectively controlling said direction of said current flowing through said electronic load circuit;

a common-mode resistor feedback circuit coupled to said electronic load circuit for generating a common mode voltage and for reducing an output impedance during transitions of said output signal; and

a current mirror coupled to said electronic load circuit for controlling said current as a function of said common mode voltage.

9. The low voltage differential signal driver circuit according to claim 8, further comprising a current source coupled to said electronic load circuit for supplying said current.

10. The low voltage differential signal driver circuit according to claim 8, further comprising a bias voltage source coupled to said current mirror for further controlling said current.

11. The low voltage differential signal driver circuit according to claim 8, wherein said low voltage differential signal driver circuit is enabled to operate in a single pole mode.

12. The low voltage differential signal driver circuit described in claim 8, wherein said common-mode resistor feedback circuit is coupled in parallel with said electronic load circuit.

13. The low voltage differential signal driver circuit described in claim 12, wherein said electronic load circuit comprises a resistive load.

14. The low voltage differential signal driver circuit described in claim 12, wherein said electronic load circuit comprises a capacitive load.

15. A method for driving a low voltage differential signal, comprising:

selectively controlling a direction of a current through an output impedance as a function of an input signal;

generating a differential output signal as a function of said direction of said current through said output impedance;

generating a common mode feedback signal as a function of said differential output signal;

controlling said current as a function of said common mode feedback signal and as a function of a bias voltage; and

modifying said output impedance during transitions of said differential output signal.

16. The method according to claim 15, wherein said modifying said output impedance is accomplished by varying a resistance of said output impedance.

17. The method according to claim 15, wherein said modifying said output impedance is accomplished by varying a capacitance of said output impedance.