High stability fast start up oscillator for implants

• US 20070247247A1
• Filed: 04/20/2006
• Published: 10/25/2007
• Est. Priority Date: 04/20/2006
• Status: Active Grant

• Current Assignee: Data Sciences U K Limited (International Business Machines Corporation)
• Original Assignee: Transoma Medical, Inc.
• Inventors: Mosesov, Oleg
• Granted Patent: US 7,489,209 B2
• Time in Patent Office: Days
• US Class Current: 331/158
• CPC Class Codes: H03B 5/06 Modifications of generator to ensure starting of oscillations
• CPC Class Codes: H03B 5/32 being a piezoelectric resonator selection of piezoelectric material H10N30/00

Abstract

An oscillator for use within an implantable medical device is provided. The oscillator includes a resonator and a first switch coupled to a first resistive network. The first resistive network provides a first electrical path through the first switch and a second electrical path not going through the switch. The oscillator additionally includes a second switch coupled to a second resistive network. The second resistive network provides a third electrical path through the second switch and a fourth electrical path not going through the switch. Furthermore, the oscillator includes a transistor, the base terminal coupled with the first resistive network and the resonator and the emitter terminal coupled to the fourth resistor. The second electrical path with the first switch opened has a substantially higher resistance than the first electrical path when the first switch is closed. In addition, the fourth electrical path with the second switch opened has a substantially higher resistance than the third electrical path when the second switch is closed.

Claims

1. An oscillator for use within an implantable medical device comprising:

a resonator;

a first switch coupled to a first resistive network, the first resistive network providing a first electrical path through the first switch and a second electrical path bypassing the switch;

a second switch coupled to a second resistive network, the second resistive network providing a third electrical path through the second switch and a fourth electrical path bypassing the switch; and

a transistor, the base terminal coupled with the first resistive network and the resonator and the emitter terminal coupled to the second resistive network,

wherein

the second electrical path with the first switch opened has a substantially higher resistance than the first electrical path when the first switch is closed; and

the fourth electrical path has a substantially higher resistance with the second switch opened than the third electrical path when the second switch is closed.

2. The oscillator of claim 1 wherein the transistor is an NPN transistor.

3. The oscillator of claim 2 further comprising a tank circuit coupled to the collector terminal of the NPN transistor.

4. The oscillator of claim 3 wherein the tank circuit comprises:

a capacitor, a third variable capacitor, and an inductor coupled in parallel.

5. The oscillator of claim 1

wherein the first resistive network comprises a first resistor coupled in parallel with the first switch, the first resistor and the first switch both further coupled in series to a second resistor;

and

wherein the second resistive network comprises a third resistor coupled in parallel with the second switch, the third resistor and the second switch both further coupled in series to a fourth resistor.

6. The oscillator of claim 1

wherein the first resistive network comprises a first resistor coupled in series with the first switch, with the first resistor and the first switch further coupled in parallel with a second resistor;

and

wherein the second network comprises a third resistor coupled in series with the second switch, with the third resistor and the second switch further coupled in parallel with a fourth resistor.

7. The oscillator of claim 1 wherein signals are input into the switches from an external source, the signals controlling an open or closed state of the switches.

8. The oscillator of claim 1 wherein the first and second switches are opened at the same time and are closed at the same time.

9. The oscillator of claim 1 wherein the resonator is made from a crystal or ceramic material.

10. The oscillator of claim 1 wherein the resonator is a 8 MHz resonator.

11. The oscillator of claim 1 wherein one or more of the switches are analog switches.

12. The oscillator of claim 1 wherein the duty cycle of the oscillator is about 1% or less.

13. A method of operation for a dual-mode oscillator comprising:

providing an oscillator including a resonator, a base switch and an emitter switch, the base switch being coupled to a first resistive network and the emitter switch being coupled to a second resistive network;

operating the oscillator within a first current mode wherein the base and emitter switches are open and a first current is applied to the resonating element through the first and second resistive networks;

receiving a signal from an external source to switch the oscillator to a second current mode; and

operating the oscillator within the second current mode wherein the base and emitter switches are closed providing a lower resistance path through the first and second resistive networks for a second current applied to the resonating element, the second current being substantially larger than the first current.

14. The method of claim 13 further comprising:

returning the oscillator to operation within the first current mode when the signal from an external source is no longer received.

15. The method of claim 13 wherein the period between the first current mode and the second current mode is less than about 1 ms.

16. The method of claim 13 wherein the first current is about 2.2-2.7 μ

A.

17. The method of claim 13 wherein the second current is about 0.5-1 mA.

18. The method of claim 13 wherein the signal is a pulsed signal.

19. The method of claim 13 wherein the duration of the pulse is about 5-10 μ

s.