Variable inductor technique

• US 20060197642A1
• Filed: 03/04/2005
• Published: 09/07/2006
• Est. Priority Date: 03/04/2005
• Status: Active Grant

• Current Assignee: 138 East LCD Advancements Limited (Vector Capital Corporation)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Hargrove, Michael, Petrosky, Joseph
• Granted Patent: US 7,598,838 B2
• Time in Patent Office: Days
• US Class Current: 336/200
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 17/0013 with stacked layers
• CPC Class Codes: H01F 2021/125 Printed variable inductor with taps, e.g. for VCO
• CPC Class Codes: H01F 21/12 discontinuously variable, e.g. tapped
• CPC Class Codes: H01L 23/5227 Inductive arrangements or effects of, or between, wiring layers other inductive arrangements H01L23/645
• CPC Class Codes: H01L 27/08 including only semiconductor components of a single kind
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H03J 2200/35 Inductance tunable by switching in/out parts of the inductor

Abstract

An integrated variable inductor is achieved by placing a second closed-loop inductor immediately above or below a primary inductor. The closed-loop configuration of the second inductor may be broken on-chip by several ways, including use of a transistor to selectively short together both ends of the second inductor. If one wishes to alter the inherent inductance characteristics of the primary inductor, the transistor coupling both ends of the second inductor is actuated. Thus, a current applied to the primary inductor induces a current in the second inductor by inductive coupling. The second current in the second inductor then alters the impedance of the primary inductor by mutual inductance. Thus, the inductance value of the primary inductor is altered. To remove the influence of the second inductor on the primary inductor, the closed-loop configuration of the second inductor is broken.

Claims

1. A variable inductor comprising:

a first inductor;

a selectively conductive current path in physical arrangement with said first inductor for permitting inductive coupling with said first inductor;

wherein said selectively conductive current path may selectively be placed in one of a first state and a second state, said first state being characterize by said current path having an open circuit configuration wherein no current may conduct within said current path, and said second state being characterized by said current path having a closed circuit configuration wherein said current path forms a closed current loop.

2. The variable inductor of claim 1, wherein:

said selectively conductive path has first and second ends selectively coupled to each other by a coupling device;

said conductive path is placed in said first state by said coupling device being set to decouple said first end from said second end; and

said conductive path is placed in said second state by said coupling device being set to couple said first end to said second end.

3. The variable inductor of claim 2, wherein said coupling device is a switching device.

4. The variable inductor of claim 3, wherein said switching device is a transistor.

5. The variable inductor of claim 1, wherein said selectively conductive path is a second inductor that establishes mutual inductance with said first inductor when said second inductor is in said second state, and provides no inductive load to said first inductor when said second inductor is in said first state.

6. The variable inductor of claim 1, wherein:

said selectively conductive path is a second inductor having an input terminal node and an output terminal node;

said second inductor is placed in said first state by selectively decoupling its input terminal node from its output terminal node; and

said second inductor is place in said second state by selectively coupling its input terminal to its output terminal node to established a closed circuit loop about said second inductor.

7. The variable inductor of claim 6, wherein said input terminal node and output terminal node are selectively coupled to, and decoupled from, each other by a coupling device.

8. The variable inductor of claim 7, wherein said coupling device is a transistor.

9. The variable inductor of claim 6, further having a plurality of said second inductors.

10. The variable inductor of claim 9, wherein said plurality of second inductors are constructed immediately above and/or below said first inductor on an integrated circuit.

11. The variable inductor of claim 10, further having a control circuit for selectively placing a select combination of said second inductors in either of said first or second states.

12. The variable inductor of claim 1, wherein said first inductor is part of an integrated circuit on a common substrate.

13. The variable inductor of claim 1, wherein said selectively conductive path is a second inductor having two end terminal nodes, said variable inductor further having;

a plurality of said second inductors concentrically arranged on a common process layer, each of said second inductors being selectively inductively coupled to said first inductor by coupling together their respective end terminal nodes.

14. The variable inductor of claim 13, further having a switching network for selectively interconnecting the end terminal nodes of said plurality second inductors.

15. The variable inductor of claim 13, wherein said plurality of second inductors are constructed immediately above or below said first inductor on an integrated circuit.

16. An integrated circuit variable inductor comprising:

a first inductor on a substrate;

a second inductor arranged on said substrate to permit inductive coupling with said first inductor, wherein said second inductor has an input node and an output node;

a coupling device for selectively coupling said input node to said output node to establish a closed circuit through said second inductor between said input and output nodes, and for selectively isolating said input node from said output node to establish an open circuit preventing current flow through said second inductor.

17. The integrated circuit variable inductor of claim 16, wherein:

said input node and output node are first and second access nodes constituting a first access node pair; and

said second inductor further includes additional access nodes for establishing a plurality of selectable access node pair combinations, and current may selectively conduct through said second inductor only between the access nodes of a selected access node pair combination.

18. The integrated circuit variable inductor of claim 16, wherein:

wherein said first inductor resides within a first set of layer including at least one layer on said common substrate, and said second inductor resides within said first set of layers.

19. The integrated circuit variable inductor of claim 16, further comprising a plurality of said second inductors concentrically arranged on a common process layer, each of said second inductors being selectively inductively coupled to said first inductor by coupling together their respective input and output nodes.

20. The integrated circuit variable inductor of claim 16, wherein:

said first inductor resides within a first layer set on said common substrate, and said second inductor resides within a second layer set on said substrate, said first and second layer sets having no layer in common.

21. The integrated circuit variable inductor of claim 16, further having a plurality of said second inductor and coupling device pairs, each second inductor being responsive to its corresponding coupling device for selectively establishing an open circuit or closed circuit through a selected second inductor.

22. A method for varying the inductive value of a first inductor on a semiconductor substrate comprising:

arranging a second inductor in proximity to said first inductor for permitting inductive coupling with said first inductor;

establishing a first inductive value for said first inductor by preventing current flow in said second inductor;

establishing a second inductive value for said first inductor by creating a short circuit through at least part of said second inductor to promote mutual inductive coupling with said first inductor.