Digital circuit decoupling for EMI reduction

• US 6,337,798 B1
• Filed: 01/25/2000
• Issued: 01/08/2002
• Est. Priority Date: 01/25/2000
• Status: Expired due to Term

• Current Assignee: Dell USA LP (Dell Technologies Inc.)
• Original Assignee: Dell USA LP (Dell Technologies Inc.)
• Inventors: Steigerwald, Todd W., Hailey, Jeffrey C.
• Primary Examiner(s): Sircus, Brian
• Assistant Examiner(s): Prasad, Chandrika
• Application Number:
  US09/491,290
• Time in Patent Office: 714 Days
• Field of Search: 361/763, 361/818, 361/760, 361/761, 361/762, 361/777, 307/91, 176/250, 176/260, 333/12, 333/186
• US Class Current: 361/763
• CPC Class Codes: H05K 1/0231 Capacitors or dielectric substances
• CPC Class Codes: H05K 2201/09309 Core having two or more power planes; Capacitive laminate of two power planes
• CPC Class Codes: H05K 2201/09481 Via in pad; Pad over filled via if used for surface mounting H05K1/113
• CPC Class Codes: H05K 2201/10522 Adjacent components
• CPC Class Codes: H05K 2201/10545 Related components mounted on both sides of the PCB
• CPC Class Codes: H05K 2201/10636 Leadless chip, e.g. chip capacitor or resistor
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A printed circuit board assembly characterized by at least two decoupling capacitors for decoupling transient currents resulting from, for example, logic transitions in high-speed digital circuitry. The decoupling capacitors are physically arranged, and electrically connected between a power plane and a ground plane, so that transient currents flow in respectively opposite directions through the capacitors, thereby maximizing the capacitors'"'"' mutual inductance, and thus minimizing the electromagnetic interference generated by the capacitors.

Claims

1. A circuit assembly comprising:

a printed circuit board (PCB) characterized by a first surface, a first conductive layer, and a second conductive layer;

first and second discrete capacitive elements, each of the capacitive elements having conductive terminals disposed at opposing extremities of the associated capacitive element, the capacitive elements mutually juxtaposed on the first surface of the PCB so that the first conductive terminal of the first capacitive element is disposed adjacent to the first conductive terminal of the second capacitive element and remotely from the second conductive terminal of the second capacitive element; and

a first conductor coupling the first conductive terminal of the first capacitive element to the first conductive layer;

a second conductor coupling the second conductive terminal of the first capacitive element to the second conductive layer;

a third conductor coupling the first conductive terminal of the second capacitive element to the second conductive layer; and

a fourth conductor coupling the second conductive terminal of the second capacitive element to the first conductive layer.

2. A circuit assembly as defined in claim 1, wherein each of the conductors comprises a via.

3. A circuit assembly as defined in claim 1 wherein the first conductor comprises a via extending between the first surface and the first conductive layer.

4. A circuit assembly as defined in claim 1, wherein the second conductor comprises a via extending between the first surface and the second conductive layer.

5. A circuit assembly as defined in claim 1, wherein the third conductor comprises a via extending between the first surface and the second conductive layer.

6. A circuit assembly as defined in claim 1, wherein the fourth conductor comprises a via extending between the first surface and the first conductive layer.

7. A circuit assembly as defined in claim 1, wherein the first conductor comprises a first pad contiguous to the first conductive terminal of the first capacitive element, the second conductor comprises a second pad contiguous to the second conductive terminal of the first capacitive element, the third conductor comprises a third pad contiguous to the first conductive terminal of the second capacitive element, and the fourth conductor comprises a fourth pad contiguous to the second conductive terminal of the second capacitive element.

8. A circuit assembly as defined in claim 7, wherein the first conductor comprises a first via coupling the first pad to the first internal conductive layer;

the second conductor comprises a second via coupling the second pad to the second internal conductive layer;

the third conductor comprises a third via coupling the third pad to the second internal conductive layer; and

the fourth conductor comprises a fourth via coupling the fourth pad to the first internal conductive layer.

9. A circuit assembly as defined in claim 8, wherein the first conductive layer is coupled to a voltage source.

10. A circuit assembly as defined in claim 9, wherein the second conductive layer is coupled to a reference potential for the voltage source.

11. A circuit assembly comprising:

a printed circuit board (PCB) characterized by a first exterior surface, a first conductive layer, and a second conductive layer;

first and second discrete capacitive elements, each of the capacitive elements having conductive terminals disposed at opposing extremities of the associated capacitive element, the capacitive elements mutually juxtaposed on the first exterior surface of the PCB so that the first conductive terminal of the first capacitive element is disposed adjacent to the first conductive terminal of the second capacitive element and remotely from the second conductive terminal of the second capacitive element; and

a conductor array coupling two of the conductive terminals to the first conductive layer and coupling two of the conductive terminals to the second conductive layer;

wherein the conductor array comprises;

a first conductor contiguous to the first conductive terminal of the first capacitive element and extending to the first conductive layer;

a second conductor contiguous to the second conductive terminal of the first capacitive element and extending to the second conductive layer;

a third conductor contiguous to the first conductive terminal of the second capacitive element and extending to the second conductive layer; and

a fourth conductor contiguous to the second conductive terminal of the second capacitive element and extending to the first conductive layer.

12. A circuit assembly as defined in claim 11, wherein the first conductive layer is a power plane and the second conductive layer is a ground plane.

13. A circuit assembly as defined in claim 11, wherein each of the conductors comprises a pad that is contiguous to a conductive terminal and a via.

14. A circuit assembly as defined in claim 13, wherein the first internal conductive layer is a power plane and the second internal conductive layer is a ground plane.

15. A circuit assembly comprising:

a printed circuit board (PCB) characterized by a first exterior surface, a second exterior surface, a first internal conductive layer, and a second internal conductive layer;

first and second discrete capacitive elements, each of the capacitive elements having respective first and second conductive terminals disposed at opposing extremities of the associated capacitive element, the first capacitive element positioned on the first exterior surface and the second capacitive element positioned on the second exterior surface, substantially orthogonally aligned with the first capacitive element; and

a conductive array selectively coupling each of the conductive terminals of the capacitive elements to either the first internal conductive layer or to the second internal conductive layer for reducing electromagnetic coupling between the capacitive elements.

16. A circuit assembly as defined in claim 15, wherein the conductor array comprises:

a first conductor contiguous to the first conductive terminal of the first capacitive element and extending to the first internal conductive layer;

a second conductor contiguous to the second conductive terminal of the first capacitive element and extending to the second internal conductive layer;

a third conductor contiguous to the first conductive terminal of the second capacitive element and extending to the second internal conductive layer; and

a fourth conductor contiguous to the second conductive terminal of the second capacitive element and extending to the first internal conductive layer.

17. A circuit assembly as defined in claim 16, wherein the first internal conductive layer is a power plane and the second internal conductive layer is a ground plane.

18. A circuit assembly as defined in claim 16, wherein each of the conductors comprises pad that is contiguous to a conductive terminal and a via.

19. A circuit assembly as defined in claim 18, wherein the first internal conductive layer is a power plane and the second internal conductive layer is a ground plane.

20. A printed circuit board (PCB) adapted for the arrangement of at least two capacitive elements, each of which capacitive elements has respective first and second conductive terminals, the PCB comprising:

an exterior surface for supporting the capacitive elements;

a first internal conductive layer;

a second internal conductive layer; and

a conductive array for selectively coupling each of the conductive terminals of the capacitive elements to either the first internal conductive layer or the second internal conductive layer and for reducing electromagnetic coupling between the capacitive elements, wherein the conductive array comprises;

a first conductor disposed for connection to the first conductive terminal of the first capacitive element and extending between the exterior surface and the first internal conductive layer;

a second conductor disposed for connection to the second conductive terminal of the first capacitive element and extending between the exterior surface and the second interior conductive layer;

a third conductor disposed for connection to the first conductive terminal of the second capacitive element and extending between the exterior surface and the second internal conductive layer; and

a fourth conductor disposed for connection to the second conductive terminal of the second capacitive element and extending between the exterior surface and the first internal conductive layer.

21. A circuit assembly as defined in claim 20, wherein the first internal conductive layer is a power plane and the second internal conductive layer is a ground plane.

22. A circuit assembly as defined in claim 20, wherein each of the conductors comprises a pad that is contiguous to a conductive terminal and a via.

23. A circuit assembly as defined in claim 22, wherein the first internal conductive layer is a power plane and the second internal conductive layer is a ground plane.

24. A circuit assembly comprising:

a printed circuit board (PCB) characterized by an exterior surface, a first conductive layer, and a second conductive layer;

first and second discrete capacitive elements, each of the capacitive elements having respective first and second conductive terminals disposed at opposing extremities of the associated capacitive element, the capacitive elements axially aligned on the exterior surface of the PCB so that the first conductive terminal of the first capacitive element is disposed remotely from the first conductive terminal of the second capacitive element and in proximity to the second conductive terminal of the second capacitive element; and

a first conductor coupling the first conductive terminal of the first capacitive element to the first conductive layer;

a second conductor coupling the second conductive terminal of the first capacitive element to the second conductive layer;

a third conductor coupling the first conductive terminal of the second capacitive element to the second conductive layer; and

a fourth conductor coupling the second conductive terminal of the second capacitive element to the first conductive layer.

25. A circuit assembly as defined in claim 24, wherein each of the conductors comprises a via.

26. A circuit assembly as defined in claim 25, wherein the first conductor comprises a first pad contiguous to the first conductive terminal of the first capacitive element, the second conductor comprises a second pad continuous to the second conductive terminal of the first capacitive element, the third conductor comprises a third pad contiguous to the first conductive terminal of the second capacitive element, and the fourth conductor comprises a fourth pad contiguous to the second conductive terminal of the second capacitive element.

27. A circuit assembly as defined in claim 26, wherein the first conductor comprises a first via coupling the first pad to the first internal conductive layer;

the second conductor comprises a second via coupling the second pad to the second internal conductive layer;

the third conductor comprises a third via coupling the third pad to the second internal conductive layer; and

the fourth conductor comprises a fourth via coupling the fourth pad to the first internal conductive layer.

28. Electronic equipment comprising a printed circuit assembly, the printed circuit assembly in turn comprising:

a printed circuit board (PCB) having a first exterior surface, a first internal conductive layer, and a second internal conductive layer;

a first discrete capacitive element having first and second conductive terminals disposed at opposing extremities of the first capacitive element;

a first conductor coupling the first conductive terminal of the first capacitive element to the first conductive layer; and

a second conductor coupling the second conductive terminal of the first capacitive element to the second conductive layer.

29. Electronic equipment as defined in claim 28, wherein the first conductor comprises a first pad contiguous to the first conductive terminal of the first capacitive element and a first via coupling the first pad to the first internal conductive layer and the second conductor comprises a second pad contiguous to the second conductive terminal of the first capacitive element and a second via coupling the second pad to the second internal conductive layer.

30. Electronic equipment as defined in claim 29, wherein the first internal conductive layer is a power plane and the second internal conductive layer is a return for the power plane.

31. Electronic equipment as defined in claim 28, wherein the printed circuit assembly further comprises:

a second capacitive element having first and second conductive terminals disposed at opposing extremities of the second capacitive elements, the second capacitive element laterally juxtaposed to the first capacitive element on the first exterior surface of the PCB;

a third conductor coupling the first conductive terminal of the second capacitive element to the second internal conductive layer; and

a fourth conductor coupling the second conductive terminal of the second capacitive element to first internal conductive layer.

32. Electronic equipment as defined in claim 31, wherein the third conductor comprises a third pad contiguous to the first conductive terminal of the second capacitive element and a third via coupling the third pad to the second internal conductive layer and the fourth conductor comprises a fourth pad contiguous to the second conductive terminal of the second capacitive element and a fourth via coupling the fourth pad to the fourth internal conductive layer.

33. Electronic equipment as defined in claim 32, wherein the first internal conductive layer is a power plane and the second internal conductive layer is a return for the power plane.

34. Electronic equipment as defined in claim 28, wherein the printed circuit assembly additionally comprises:

a PCB having a second exterior surface substantially parallel to the first exterior surface;

a second discrete capacitive element having first and second conductive terminals disposed at opposing extremities of the second capacitive element, the second capacitive element position on the second exterior surface at a position orthogonally juxtaposed to the first capacitive element;

a third conductor coupling the first conductive terminal of the second capacitive element to the second internal conductive layer; and

a fourth conductor coupling the second conductive terminal of the second capacitive element o first internal conductive layer.

35. Electronic equipment as defined in claim 34, wherein the third conductor comprises a third pad contiguous to the first conductive terminal of the second capacitive element and a third via coupling the third pad to the second internal conductive layer and the fourth conductor comprises a fourth pad contiguous to the second conductive terminal of the second capacitive element and a fourth via coupling the fourth pad to the fourth internal conductive layer.

36. Electronic equipment as defined in claim 35, wherein the first internal conductive layer is a power plane and the second internal conductive layer is a return for the power plane.