Current starved inverter ring oscillator having an in-phase signal transmitter with a sub-threshold current control unit

• US 6,803,831 B2
• Filed: 05/16/2003
• Issued: 10/12/2004
• Est. Priority Date: 05/20/2002
• Status: Expired due to Fees

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Nishikido, Ryoji
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Chang, Joseph
• Application Number:
  US10/439,873
• Publication Number:
  US 20030214361A1
• Time in Patent Office: 515 Days
• Field of Search: 331/57, 331/17, 331/117.R
• US Class Current: 331/57
• CPC Class Codes: H03K 3/0231 Astable circuits H03K3/0315 takes precedence
• CPC Class Codes: H03K 3/0315 Ring oscillators

Abstract

A ring oscillator according to the present invention comprises:

a ring oscillation unit, including

a current starved inverter CSI having a current control P channel transistor P2, a signal transmission P channel transistor P3, a signal transmission N channel transistor N3 and a current control N channel transistor N2, and

an in-phase signal transmitter receiving a signal from the current starved inverter, and outputting an in-phase signal to the current starved inverter; and

a current control unit, including

a basic current source having P channel transistor P10 and an N channel transistor N10 which is operated in a weak inversion state and flows a subthreshold current, and

a current mirror circuit having a P channel transistor P12current-mirror connected to the P channel transistors P10 and P2, and an N channel transistor N12 current-mirror connected to the N channel transistor N2.

Claims

1. A ring oscillator comprising:

a current control unit, including

a basic current source having a series circuit formed of a first P channel transistor, the drain and the gate of which are connected, and a first N channel transistor, the drain of which is connected to the drain of the first P channel transistor and which, to supply a sub-threshold current, is operated in a weak inversion state, and

a current mirror circuit having a series circuit formed of a second P channel transistor, the gate of which is connected to the drain of the first P channel transistor, a second N channel transistor, the drain and the gate of which are connected to the drain of the second P channel transistor; and

a ring oscillation unit, including

a current starved inverter, having

a current control P channel transistor, the source of which is connected to the power source and the gate of which is connected to the drain of the first P channel transistor of the basic current source,

a signal transmission P channel transistor, the source of which is connected to the drain of the current control P channel transistor,

a signal transmission N channel transistor, the drain of which is connected to the drain of the signal transmission P channel transistor, and

a current control N channel transistor, the drain of which is connected to the source of the signal transmission N channel transistor, the gate of which is connected to the drain of the second N channel transistor of the current mirror circuit, and the source of which is grounded,

wherein a connection point of the gate of the signal transmission P channel transistor and the gate of the signal transmission N channel transistor serves as a signal input terminal, and a connection point of the drain of the signal transmission P channel transistor and the drain of the signal transmission N channel transistor serves as an output terminal for outputting an inverted signal; and

an in-phase signal transmitter for receiving an input signal from the output terminal of the current starved inverter, and for outputting, to the input terminal of the current starved inverter and to an external device, a signal having the same phase as the input signal.

2. A ring oscillator according to claim 1, wherein, in the basic current source of the current control unit, the first P channel transistor, the first N channel transistor and a resistor are connected in series between a power source and a ground terminal;

and wherein a bandgap reference voltage is applied to the gate of the first N channel transistor.

3. A ring oscillator according to claim 1,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor; and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a bias generating resistor.

4. A ring oscillator according to claim 1,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor;

and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a fourth N channel transistor, the gate of which is connected to the power source.

5. A ring oscillator according to claim 1,

wherein the ring oscillation unit further includes a capacitor provided between the output terminal of the current starved inverter and the ground terminal;

and

wherein the in-phase signal transmitter consists of a Schmit trigger circuit, for outputting an in-phase signal of an input signal, a circuit threshold value of which represents a hysteresis characteristic relative to the change of an input signal.

6. A ring oscillator according to claim 5, wherein, in the basic current source of the current control unit, the first P channel transistor, the first N channel transistor and a bias generating resistor are connected in series between a power source and a ground terminal;

and wherein a bandgap reference voltage is applied to the gate of the first N channel transistor.

7. A ring oscillator according to claim 5,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor;

and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a bias generating resistor.

8. A ring oscillator according to claim 5,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor;

and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a fourth N channel transistor, the gate of which is connected to the power source.

9. A ring oscillator according to claim 1, wherein the in-phase signal transmitter consists of a current starved inverter group including an even number of current starved inverters connected in series.

10. A ring oscillator according to claim 9, wherein, in the basic current source of the current control unit, the first P channel transistor, the first N channel transistor and a bias generating resistor are connected in series between a power source and a ground terminal;

and wherein a bandgap reference voltage is applied to the gate of the first N channel transistor.

11. A ring oscillator according to claim 9,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor;

and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a bias generating resistor.

12. A ring oscillator according to claim 9,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor;

and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a fourth N channel transistor, the gate of which is connected to the power source.

17. A ring oscillator according to claim 1, wherein the ring oscillation unit further includes

a capacitor located between the output terminal of the current starved inverter and the ground terminal,

a current supplying P channel transistor selector, including at least one series circuit formed of a current supplying P channel transistor, which is located between the power source and the drain of the current control P channel transistor in the current starved inverter and the gate of which is connected to the drain of the first P channel transistor in the basic current source, and a switching P channel transistor, for receiving a select signal at the gate, and

a current supplying N channel transistor selector, including at least one series circuit formed of a current supplying N channel transistor, which is located between the ground terminal and the drain of the current control N channel transistor in the current starved inverter and the gate of which is connected to the drain of the second N channel transistor in the current mirror circuit, and a switching N channel transistor, for receiving a select signal at the gate;

wherein the in-phase signal transmitter consists of a Schmit trigger circuit, for outputting an in-phase signal of san input signal, the circuit threshold value of which represents a hysteresis characteristic relative to the change of the input signal.

18. A ring oscillator according to claim 17, wherein, in the basic current source of the current control unit, the first P channel transistor, the first N channel transistor and a bias generating resistor are connected in series between a power source and a ground terminal;

and wherein a bandgap reference voltage is applied to the gate of the first N channel transistor.

19. A ring oscillator according to claim 17,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor;

and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a bias generating resistor.

20. A ring oscillator according to claim 17,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor;

and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a fourth N channel transistor, the gate of which is connected to the power source.

13. A ring oscillator comprising:

a current control unit, including

a basic current source having a series circuit formed of a first P channel transistor, the drain and the gate of which are connected, and a first N channel transistor, the drain of which is connected to the drain of the first P channel transistor and which, to supply a sub-threshold current, is operated in a weak inversion state,

current mirror circuit having a series circuit formed of a second P channel transistor, the gate of which is connected to the drain of the first P channel transistor, a second N channel transistor, the drain and the gate of which are connected to the drain of the second P channel transistor; and

a ring oscillation unit, including

a current starved inverter, having

a current control P channel transistor, the source of which is connected to the power source and the gate of which is connected to the drain of the first P channel transistor of the basic current source,

a signal transmission P channel transistor, the source of which is connected to the drain of the current control P channel transistor,

a signal transmission N channel transistor, the drain of which is connected to the drain of the signal transmission P channel transistor, and

a current control N channel transistor, the drain of which is connected to the source of the signal transmission N channel transistor, the gate of which is connected to the drain of the second N channel transistor of the current mirror circuit, and the source of which is grounded,

a Schmit trigger circuit, for outputting an in-phase signal of an input signal, a circuit threshold value of which represents a hysteresis characteristic relative to the change of the input signal, and the output terminal of which is connected to the input terminal of the current starved inverter

a resistance setting circuit, located between the output terminal of the current starved inverter and the input terminal of the Schmit trigger circuit, and formed of a parallel connection of multiple series circuits, each having a resistor and a switching element, and

capacitance setting circuit, located between the input terminal of the Schmit trigger circuit and the ground terminal, and formed of a parallel connection of multiple series circuits, each having a capacitor and a switching element.

14. A ring oscillator according to claim 13, wherein, in the basic current source of the current control unit, the first P channel transistor, the first N channel transistor and a bias generating resistor are connected in series between a power source and a ground terminal;

and wherein a bandgap reference voltage is applied to the gate of the first N channel transistor.

15. A ring oscillator according to claim 13,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor; and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a bias generating resistor.

16. A ring oscillator according to claim 13,

wherein the current control unit further includes a second current source constituted by a series connection, between the power source and the ground terminal, a third P channel transistor, the gate of which is connected to the drain of the first P channel transistor, and a third N channel transistor, the drain and the gate of which are connected to the gate of the first N channel transistor;

and

wherein the basic current source is constituted by a series connection, between the power source and the ground terminal, the first P channel transistor, the first N channel transistor and a fourth N channel transistor, the gate of which is connected to the power source.