Programmable logic integrated circuit devices with differential signaling capabilities

• US 6,433,579 B1
• Filed: 05/22/2001
• Issued: 08/13/2002
• Est. Priority Date: 07/02/1998
• Status: Expired due to Term

• Current Assignee: Altera Corporation (Intel Corporation)
• Original Assignee: Altera Corporation (Intel Corporation)
• Inventors: Chong, Yan, Sung, Chiakang, Huang, Joseph, Wang, Xiaobao, Pan, Philip, Wang, Bonnie I., Nguyen, Khai, Kim, In Whan, Rangan, Gopinath
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): Tan, Vibol
• Application Number:
  US09/863,143
• Time in Patent Office: 448 Days
• Field of Search: 326/38-41, 326/86, 326/83, 326/90, 326/119, 326/121
• US Class Current: 326/38
• CPC Class Codes: H03K 19/018521 of complementary type, e.g. CMOS
• CPC Class Codes: H03K 19/17744 for input/output signals
• CPC Class Codes: H03K 19/1778 Structural details for adapting physical parameters
• CPC Class Codes: H03K 19/17784 for supply voltage
• CPC Class Codes: H03K 19/17792 for operating speed

Abstract

A programmable logic device is equipped for various differential signaling schemes by providing a differential output buffer on the device that can be configured according to the needs of the particular differential signaling schemes that may be used. The buffer includes a differential output driver, an adjustable current limiting circuit between the supply voltage and the differential output driver, and an adjustable current limiting circuit between the differential output driver and ground. By selectively adjusting the two current limiting circuits, the output impedance and current, as well as the common mode output voltage and the differential output voltage can be controlled.

Claims

1. A programmable logic device comprising:

at least one of (a) a voltage source, and (b) a ground terminal;

a pair of output terminals;

a differential output driver for driving said pair of output terminals in accordance with a differential signaling scheme; and

a programmable current-limiting circuit operatively connected to said differential output driver for selectably configuring said differential output driver for use with any one of a plurality of differential signaling schemes;

wherein;

said programmable current-limiting circuit comprises at least one programmable current-limiting portion connected between (1) said differential output driver, and (2) said one of (a) said voltage source, and (b) said ground terminal; and

said at least one programmable current-limiting portion comprises;

at least one current-limiting component, and

for each one of said at least one current-limiting component, a programmable switch for selectably connecting said one of said at least one current-limiting component between (1) said differential output driver, and (2) said one of (a) said voltage source, and (b) said ground terminal.

2. The programmable logic device of claim 1 comprising:

said voltage source; and

said ground terminal;

wherein;

said at least one programmable current-limiting portion comprises;

a first programmable current-limiting portion connected between said voltage source and said differential output driver; and

a second programmable current-limiting portion connected between said differential output driver and said ground terminal.

3. The programmable logic device of claim 2 wherein said first programmable current-limiting portion comprises:

at least one first current-limiting component; and

for each one of said at least one first current-limiting component, a programmable switch for selectably connecting said one of said at least one first current-limiting component between said voltage source and said differential output driver.

4. The programmable logic device of claim 3 wherein said first current-limiting component is selected from the group consisting of a resistor, a capacitor, a transistor and combinations thereof.

5. The programmable logic device of claim 4 wherein said programmable switch comprises a pass gate.

6. The programmable logic device of claim 5 wherein said pass gate is controlled by a configuration bit.

7. The programmable logic device of claim 3 wherein said programmable switch comprises a pass gate.

8. The programmable logic device of claim 7 wherein said pass gate is controlled by a configuration bit.

9. The programmable logic device of claim 2 wherein said second programmable current-limiting portion comprises:

at least one second current-limiting component; and

for each one of said at least one second current-limiting component, a programmable switch for selectably connecting said one of said at least one second current-limiting component between said differential output driver and said ground terminal.

10. The programmable logic device of claim 9 wherein said second current-limiting component is selected from the group consisting of a resistor, a capacitor, a transistor and combinations thereof.

11. The programmable logic device of claim 10 wherein said programmable switch comprises a pass gate.

12. The programmable logic device of claim 11 wherein said pass gate is controlled by a configuration bit.

13. The programmable logic device of claim 9 wherein said programmable switch comprises a pass gate.

14. The programmable logic device of claim 13 wherein said pass gate is controlled by a configuration bit.

15. The programmable logic device of claim 1 wherein said current-limiting component is selected from the group consisting of a resistor, a capacitor, a transistor and combinations thereof.

16. The programmable logic device of claim 15 wherein said programmable switch comprises a pass gate.

17. The programmable logic device of claim 16 wherein said pass gate is controlled by a configuration bit.

18. The programmable logic device of claim 1 wherein said programmable switch comprises a pass gate.

19. The programmable logic device of claim 15 wherein said pass gate is controlled by a configuration bit.

20. The programmable logic device of claim 1 wherein said plurality of differential signaling schemes comprises Low Voltage Differential Signaling, Bus Low Voltage Differential Signaling, Low Voltage Emitter-Coupled Logic, Low Voltage Positive Emitter-Coupled Logic, Current Mode Logic and Lightning Data Transport.

21. A digital processing system comprising:

processing circuitry;

a memory coupled to said processing circuitry; and

a programmable logic device as defined in claim 1 coupled to the processing circuitry and the memory.

22. A printed circuit board on which is mounted a programmable logic device as defined in claim 1.

23. The printed circuit board defined in claim 22 further comprising:

memory circuitry mounted on the printed circuit board and coupled to the programmable logic device.

24. The printed circuit board defined in claim 23 further comprising:

a memory mounted on the printed circuit board and coupled to the memory circuitry.

25. The printed circuit board defined in claim 23 further comprising:

processing circuitry mounted on the printed circuit board and coupled to the memory circuitry.

27. The differential output circuit of claim 21 comprising:

said voltage source; and

said ground terminal;

wherein;

said at least one programmable current-limiting portion comprises;

a first programmable current-limiting portion connected between said voltage source and said differential output driver; and

a second programmable current-limiting portion connected between said differential output driver and said ground terminal.

28. The differential output circuit of claim 27 wherein said first programmable current-limiting portion comprises:

at least one first current-limiting component; and

for each one of said at least one first current-limiting component, a programmable switch for selectably connecting said one of said at least one first current-limiting component between said voltage source and said differential output driver.

29. The differential output circuit of claim 28 wherein said first current-limiting component is selected from the group consisting of a resistor, a capacitor, a transistor and combinations thereof.

30. The differential output circuit of claim 29 wherein said programmable switch comprises a pass gate.

31. The differential output circuit of claim 30 wherein said pass gate is controlled by a configuration bit.

32. The differential output circuit of claim 28 wherein said programmable switch comprises a pass gate.

33. The differential output circuit of claim 32 wherein said pass gate is controlled by a configuration bit.

34. The differential output circuit of claim 27 wherein said second programmable current-limiting portion comprises:

at least one second current-limiting component; and

for each one of said at least one second current-limiting component, a programmable switch for selectably connecting said one of said at least one second current-limiting component between said differential output driver and said ground terminal.

35. The differential output circuit of claim 34 wherein said second current-limiting component is selected from the group consisting of a resistor, a capacitor, a transistor and combinations thereof.

36. The differential output circuit of claim 35 wherein said programmable switch comprises a pass gate.

37. The differential output circuit of claim 36 wherein said pass gate is controlled by a configuration bit.

38. The differential output circuit of claim 34 wherein said programmable switch comprises a pass gate.

39. The differential output circuit of claim 38 wherein said pass gate is controlled by a configuration bit.

26. A differential output circuit comprising:

at least one of (a) a voltage source, and (b) a ground terminal;

a pair of output terminals;

a differential output driver for driving said pair of output terminals in accordance with a differential signaling scheme; and

a programmable current-limiting circuit operatively connected to said differential output driver for selectably configuring said differential output driver for use with any one of a plurality of differential signaling schemes;

wherein;

said programmable current-limiting circuit comprises at least one programmable current-limiting portion connected between (1) said differential output driver, and (2) said one of (a) said voltage source, and (b) said ground terminal; and

said at least one programmable current-limiting portion comprises;

at least one current-limiting component, and

for each one of said at least one current-limiting component, a programmable switch for selectably connecting said one of said at least one current-limiting component between (1) said differential output driver, and (2) said one of (a) said voltage source, and (b) said ground terminal.

40. The differential output circuit of claim 26 wherein said current-limiting component is selected from the group consisting of a resistor, a capacitor, a transistor and combinations thereof.

41. The differential output circuit of claim 40 wherein said programmable switch comprises a pass gate.

42. The differential output circuit of claim 41 wherein said pass gate is controlled by a configuration bit.

43. The differential output circuit of claim 26 wherein said programmable switch comprises a pass gate.

44. The differential output circuit of claim 43 wherein said pass gate is controlled by a configuration bit.

45. The differential output circuit of claim 26 wherein said plurality of differential signaling schemes comprises Low Voltage Differential Signaling, Bus Low Voltage Differential Signaling, Low Voltage Emitter-Coupled Logic, Low Voltage Positive Emitter-Coupled Logic, Current Mode Logic and Lightning Data Transport.

46. A digital processing system comprising:

processing circuitry;

a memory coupled to said processing circuitry; and

a programmable logic device comprising a differential output circuit as defined in claim 43 coupled to the processing circuitry and the memory.

47. A printed circuit board on which is mounted a programmable logic device comprising a differential output circuit as defined in claim 26.

48. The printed circuit board defined in claim 47 further comprising:

memory circuitry mounted on the printed circuit board and coupled to the programmable logic device.

49. The printed circuit board defined in claim 48 further comprising:

a memory mounted on the printed circuit board and coupled to the memory circuitry.

50. The printed circuit board defined in claim 48 further comprising:

processing circuitry mounted on the printed circuit board and coupled to the memory circuitry.