LOW VOLTAGE DIFFERENTIAL VOLTAGE-CONTROLLED RING OSCILLATOR

• US 20020057135A1
• Filed: 05/01/2000
• Published: 05/16/2002
• Est. Priority Date: 05/01/2000
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Nelson, Dale, Sun, Lizhong
• Granted Patent: US 6,396,357 B1
• Time in Patent Office: Days
• US Class Current: 331/57
• CPC Class Codes: H03K 3/0315 Ring oscillators
• CPC Class Codes: H03K 3/354 Astable circuits

Abstract

A ring oscillator including a voltage-to-current converter for producing at least one control current from at least one control voltage and, a plurality of delay cells coupled to the converter, wherein at least one output of the one of the delay cells is coupled to the input of another of the delay cells, wherein the voltage-to-current converter produces a substantially linear output when the at least one control voltage is varied between zero volts and a rail supply voltage. Since the ring oscillator operates from a low voltage source, it can be used in applications where power supply (e.g., battery size) is small (e.g., pagers, cellular phone applications).

Claims

1. A ring oscillator comprising:

a voltage-to-current converter for producing at least one control current from at least one control voltage; and

,

a plurality of delay cells coupled to the converter, wherein at least one output of the one of the delay cells is coupled to the input of another of the delay cells,

wherein the voltage-to-current converter produces a substantially linear output when the at least one control voltage is varied between zero volts and a rail supply voltage.

2. The ring oscillator of claim 1, wherein the at least one control voltage is in a range from zero volts to approximately 2 volts.

3. The ring oscillator of claim 1, wherein the at least one control voltage is in a range from 0.01 volts to 1.5 volts.

4. The ring oscillator of claim 1, wherein the voltage-to-current converter includes at least two stages, a first stage for producing a first component of the control current, and a second stage for producing a second component of the control current.

5. The ring oscillator of claim 4, wherein the first stage of the voltage-to-current converter comprises:

a first transistor having a gate terminal coupled to the at least one control voltage; and

,

a second transistor having a gate terminal coupled to a source of the first transistor.

6. The ring oscillator of claim 5, wherein a first stage of the voltage-to-current converter further comprises:

a third transistor having a gate terminal and a drain terminal coupled to a drain of the second transistor; and

,

a fourth transistor having a gate terminal coupled to the drain of the second transistor.

7. The ring oscillator of claim 6, wherein the first, second, third and fourth transistors comprise Metal-Oxide Semiconductor Field Effect Transistors.

8. The ring oscillator of claim 4, wherein the second stage of the voltage-to-current converter comprises:

a first transistor having a gate terminal coupled to the at least one control voltage;

a second transistor having a gate terminal coupled to a drain of the first transistor; and

,

a third transistor having a gate terminal coupled to a drain of the first transistor.

9. The ring oscillator of claim 8, wherein the second stage of the voltage-to-current converter further comprises:

a fourth transistor having a drain terminal coupled to a drain terminal of the third transistor.

10. The ring oscillator of claim 9, wherein the first, second, third and fourth transistors comprise Metal-Oxide Semiconductor Field Effect Transistors.

11. The ring oscillator of claim 1, wherein each of the plurality of delay cells comprise:

at least four transistors having their gates coupled to a bias voltage generated from the control current; and

,

at least two differential input transistors; and

,

at least two cross-coupled transistors.

12. The ring oscillator of claim 11, wherein each of the plurality of delay cells additionally comprise:

at least two diodes for limiting voltage swing.

13. The ring oscillator of claim 11, wherein the at least four transistors, the at least two differential input transistors and the at least two cross-coupled transistors comprise Metal-Oxide Semiconductor Field Effect Transistors.

14. The ring oscillator of claim 1, wherein each of the plurality of delay cells includes:

at least one first input terminal;

at least one second input terminal; and

,

at least one first output terminal.

15. The ring oscillator of claim 14, wherein the at least one first input terminal, the at least one second input terminal and the at least one first output terminal each comprise a pair of terminals.

16. The ring oscillator of claim 1, wherein the rail supply voltage is in a range from zero to 2 volts.

19. The ring oscillator of claim 18, wherein the voltage-to-current converter includes at least one additional stage, said at least one additional stage generating a bias voltage from said at least one control current.

17. A ring oscillator comprising:

a voltage-to-current converter for producing at least one control current from at least one control voltage; and

,

a plurality of delay cells coupled to the converter, wherein at least one output of the one of the delay cells is coupled to the input of another of the delay cells,

wherein the plurality of delay cells each include at least one transistor with a gate terminal biased by a bias voltage generated from the at least one control current.

18. A ring oscillator comprising:

a voltage-to-current converter for producing at least one control current from at least one control voltage; and

,

a plurality of delay cells coupled to the converter, wherein at least one output of the one of the delay cells is coupled to the input of another of the delay cells,

wherein the voltage-to-current converter includes at least two stages, a first stage for producing a first component of the control current, and a second stage for producing a second component of the control current.

20. A voltage-to-current converter comprising:

a plurality of MOS transistors; and

at least two resistors having approximately the same resistance,

wherein the voltage-to-current converter produces a substantially linear output when an input voltage is varied between zero volts and a rail supply voltage.

21. The voltage-to-current converter of claim 21, wherein the input voltage is in a range from zero volts to approximately 2 volts.

22. The voltage-to-current converter of claim 20, wherein the plurality of MOS transistors are formed in first and second stages.

23. The voltage-to-current converter of claim 22, wherein the first stage of the plurality of MOS transistors comprises:

a first MOS transistor having a gate terminal coupled to the at least one input voltage; and

,

a second transistor having a gate terminal coupled to a source of the first transistor.

24. The voltage-to-current converter of claim 23, wherein the first stage of the plurality of MOS transistors further comprises:

a third transistor having a gate terminal and a drain terminal coupled to a drain of the second transistor; and

,

a fourth transistor having a gate terminal coupled to the drain of the second transistor.

25. The voltage-to-current converter of claim 22, wherein the second stage of the plurality of MOS transistors comprises:

a first transistor having a gate terminal coupled to the at least one input voltage;

a second transistor having a gate terminal coupled to a drain of the first transistor; and

,

a third transistor having a gate terminal coupled to a drain of the first transistor.

26. The voltage-to-current converter of claim 25, wherein the second stage of the plurality of MOS transistors comprises:

a fourth transistor having a drain terminal coupled to a drain terminal of the third transistor.