XTAL oscillator

• US 20140062609A1
• Filed: 08/31/2012
• Published: 03/06/2014
• Est. Priority Date: 08/31/2012
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Lee, Chang-Hyeon, Kabalican, Lindel
• Granted Patent: US 8,866,557 B2
• Time in Patent Office: Days
• US Class Current: 331/116.FE
• CPC Class Codes: H03B 2200/0034 including a buffer amplifier
• CPC Class Codes: H03B 2200/0036 including an emitter or source coupled transistor pair or a long tail pair
• CPC Class Codes: H03B 2200/0062 Bias and operating point
• CPC Class Codes: H03B 2200/0088 Reduction of noise
• CPC Class Codes: H03B 2202/027 the noise being essentially proportional to the inverse of the frequency, i.e. the so-called 1/f noise
• CPC Class Codes: H03B 5/364 the amplifier comprising field effect transistors H03B5/366 takes precedence

Abstract

Resistor bias circuitry is included in components of an XTAL oscillator system to reduce 1/f noise. An XTAL oscillator includes a resistor bias circuit attached to the XTAL core. A common mode feedback OP amp connected to the XTAL core also includes a resistor bias circuit. An XTAL oscillator chain includes an XTAL core, common mode feedback OP amp, common mode logic buffer (CML BF), and differential to CMOS converter (D2C) each with resistor bias circuitry.

Claims

1. A crystal oscillator comprising:

a crystal oscillator core;

a current generator;

a transistor (M1) connected to an output of the current generator and to inputs of the crystal oscillator core;

a first resistor bias circuit connected to the transistor (M1) and further to the crystal oscillator core between ground and a common input to the crystal oscillator core, and

wherein the first resistor bias circuit reduces 1/f noise of the crystal oscillator.

2. A crystal oscillator, as per claim 1, wherein the crystal oscillator core further comprises a cross-coupled RC circuit.

3. A crystal oscillator, as per claim 1, wherein the crystal oscillator further comprises a common mode feedback OP amp.

4. A crystal oscillator, as per claim 3, wherein the common mode feedback OP amp further comprises a second resistor bias circuit.

5. A crystal oscillator, as per claim 4, wherein the second resistor bias circuit comprises:

a fourth branch with a fourth resistor connected between a first common mode feedback OP amp transistor and a second common mode feedback OP amp transistor, a fifth branch with a fifth resistor connected between the second common mode feedback OP amp transistor and ground, and a sixth branch with a sixth resistor connected between ground and a common input to the common mode feedback OP amp.

6. A crystal oscillator, as per claim 1, further comprising a common mode logic buffer.

7. A crystal oscillator, as per claim 6, wherein the common mode logic buffer further comprises a third resistor bias circuit.

8. A crystal oscillator, as per claim 1, further comprising a differential to CMOS converter.

9. A crystal oscillator, as per claim 8, wherein the differential to CMOS converter further comprises a fourth resistor bias circuit.

10. A crystal oscillator, as per claim 1, further comprising an output CMOS buffer.

11. A crystal oscillator, as per claim 1, wherein the crystal oscillator is operative in any of:

set top box, satellite tuner, base station, mobile communications circuitry, LTE circuitry and MIMO circuitry.

12. A crystal oscillator, as per claim 1, wherein the crystal oscillator is operative in a phase-locked loop.

13. A crystal oscillator, as per claim 1, wherein the crystal oscillator provides timing signals to chips within communication systems.

14. A crystal oscillator system comprising:

a crystal oscillator core with first resistance bias circuitry;

a common mode feedback OP amp operative with the crystal oscillator core, the common mode feedback OP amp further comprising second resistance bias circuitry;

a common mode logic buffer connected to the crystal oscillator core and further comprising third resistance bias circuitry;

a differential to CMOS converter connected to the common mode logic buffer and further comprising fourth resistance bias circuitry, and

wherein each of the resistance bias circuits reduces jitter of the crystal oscillator system.

15. A crystal oscillator, as per claim 14, further comprising a CMOS output buffer connected to the differential to CMOS converter.

16. A crystal oscillator system, as per claim 14, wherein the crystal oscillator system is operative in any of:

set top box, satellite tuner, base station, mobile communications circuitry, LTE circuitry and MIMO circuitry.

17. A crystal oscillator, as per claim 14, wherein the crystal oscillator is operative in a phase-locked loop.

18. A crystal oscillator system, as per claim 14, wherein the crystal oscillator system provides timing signals to chips within communication systems.

19. A crystal oscillator comprising:

a crystal oscillator core;

a current generator;

a transistor (M1) connected to an output of the current generator;

a resistor bias circuit connected to the crystal oscillator core comprising;

a first branch with a first resistor connected between the transistor (M1) and a transistor (M2) of the crystal oscillator core,

a second branch with a second resistor connected between the transistor (M1) and a transistor (M3) of the crystal oscillator core, and

a third branch with a bias resistor connected between ground and a common input to the crystal oscillator core, and

wherein the resistance bias circuit reduces 1/f noise of the crystal oscillator.

20. A crystal oscillator, as per claim 19, wherein the crystal oscillator system is operative in any of:

set top box, satellite tuner, base station, mobile communications circuitry, LTE circuitry and MIMO circuitry.