METHODS AND APPARATUS FOR GENERATING A HIGH SWING IN AN OSCILLATOR

• US 20170353157A1
• Filed: 06/03/2016
• Published: 12/07/2017
• Est. Priority Date: 06/03/2016
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Mukherjee, Subhashish, Shrivastava, Kumar Anurag, Bonu, Madhulatha
• Granted Patent: US 10,483,909 B2
• Time in Patent Office: Days
• CPC Class Codes: H03B 5/04 Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature
• CPC Class Codes: H03B 5/06 Modifications of generator to ensure starting of oscillations
• CPC Class Codes: H03B 5/1221 the amplifier comprising multiple amplification stages connected in cascade
• CPC Class Codes: H03B 5/1234 and comprising means for varying the output amplitude of the generator H03B5/1278 takes precedence
• CPC Class Codes: H03L 3/00 Starting of generators
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation

Abstract

Methods and apparatus are disclosed to generate an oscillating output signal having a voltage swing greater than a voltage swing across nodes of active devices. An example oscillator includes a tank to generate an oscillating output signal in response receiving an edge of an enable signal; a feedback generator including a first gain stage forming a first feedback loop with the tank, the first feedback loop providing a first charge to maintain the oscillating output signal and a second gain stage forming a second feedback loop with the tank, the second feedback loop providing a second charge to maintain the oscillating output signal, the first and second charges combining with the oscillating output signal to generate a high voltage swing; and an attenuator connected between the tank and the feedback generator to isolate the tank from active components of the feedback generator.

Claims

1. An oscillator comprising:

a tank to generate an oscillating output signal in response receiving an edge of an enable signal;

a feedback generator including;

a first loop forming a first feedback loop with the tank, the first feedback loop providing a first charge to maintain the oscillating output signal; and

a second loop forming a second feedback loop with the tank, the second feedback loop providing a second charge to maintain the oscillating output signal, the first and second charges combining with the oscillating output signal to generate a high voltage swing; and

an attenuator connected between the tank and the feedback generator to isolate the tank from active components of the feedback generator.

2. The oscillator of claim 1, wherein a peak voltage of the high voltage swing is greater than a breakdown voltage of the active components in the feedback generator.

3. The oscillator of claim 1, further including an oscillation starter to output the enable signal.

4. The oscillator of claim 1, wherein the feedback generator is structured to provide the first charge at a first phase and a second phase at a second phase, the first phase and the second phase being 180 degrees out of phase with respect to each other.

5. The oscillator of claim 1, wherein the tank ceases to generate the oscillating output signal in response to a lowering of the enable signal from a first voltage to a second voltage.

6. The oscillator of claim 1, wherein the oscillating output signal corresponds to a voltage differential between a first node voltage at a first node of the tank and a second node voltage at a second node of the tank.

7. The oscillator of claim 6, wherein the first loop includes a sine-to-square wave converter to convert an oscillating voltage at the first node of the tank to a square wave.

8. The oscillator of claim 7, wherein the sine-to-square wave converter is structured to amplify the oscillating voltage.

9. The oscillator of claim 8, wherein the first loop includes a logic gate to output a first voltage when the enable signal and the output of the sine-to-square wave converter are above a threshold.

10. The oscillator of claim 9, wherein the attenuator includes coupling capacitors to isolate the first node from the sine-to-square wave converter and the logic gate.

11. The oscillator of claim 9, wherein the logic gate is structured to output a second voltage greater than the first voltage when at least one of the enable signal or the output of the sine-to-square wave converter are below the threshold.

12. The oscillator of claim 11, wherein the first loop is structured to provide the first charge to the oscillating output signal by transmitting the output of the logic gate to the first node.

13. The oscillator of claim 11, wherein the first loop is structured to provide a third charge to the oscillating output signal by transmitting the output of the sine-to-square wave converter to the second node via a coupling capacitor, the third charge providing phase correction to the tank.

14. The oscillator of claim 6, wherein the second loop includes a sine-to-square wave converter to convert an oscillating voltage at the second node of the tank to a square wave.

15. The oscillator of claim 14, wherein the sine-to-square wave converter is structured to amplify the oscillating voltage.

16. The oscillator of claim 15, wherein the second loop includes a logic gate to output a first voltage when a complementary enable voltage and the output of the sine-to-square wave converter are below a threshold.

17. The oscillator of claim 16, wherein the attenuator includes coupling capacitors to isolate the second node from the sine-to-square wave converter and the logic gate.

18. The oscillator of claim 16, wherein the logic gate is structured to output a second voltage lower than the first voltage when at least one of the complementary enable voltage or the output of the sine-to-square wave converter are above the threshold.

19. The oscillator of claim 18, wherein the second loop is structured to provide the second charge to the oscillating output signal by transmitting the output of the logic gate to the second node.

20. The oscillator of claim 18, wherein the second loop is structured to provide a third charge to the oscillating output signal by transmitting the output of the sine-to-square wave converter to the first node via a coupling capacitor, the third charge providing phase correction to the tank.

21. The oscillator of claim 1, wherein the tank includes a first inductor and a second inductor coupled to the first inductor, the first inductor and the second inductor being mutually coupled.

22. The oscillator of claim 21, wherein the oscillating output signal is a voltage difference at a first node connected to a first terminal of the first inductor and a second node connected to a terminal of the second inductor.

23. The oscillator of claim 1, wherein the feedback generator includes a fully differential amplifier to:

receive a first oscillating signal of a first node in the tank and a second oscillating signal of a second node in the tank, the first oscillating signal and the second oscillating signal oscillating 180 degrees out of phase with respect to each other,

output a third oscillating signal opposite the first oscillating signal, the third oscillating signal being amplified; and

output a fourth oscillating signal opposite the second oscillating signal, the fourth oscillating signal being amplified.

24. The oscillator of claim 23, wherein:

the first loop includes a first sine-to-square wave converter to convert the third oscillating signal into a first square wave; and

the second loop includes a second sine-to-square wave converter to convert the fourth oscillating signal into a second square wave, the first and second square waves providing charge to maintain the oscillating output signal.