Programmable analog array and method
AssigneeMotorola, Inc.
InventorsDavid J. Anderson, Danny A. Bersch
Life of this patent
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Abstract
A system for laying out a capacitor array (400) implements a programmable capacitor (33-39) whose operation is controlled with a binary control word. A programmable capacitance is produced by coupling binary weighted, switchable capacitors (101-107) between terminals (51, 52) of the programmable capacitor. The capacitor array includes two or more unit capacitors (101, 103) of unequal areas. The other capacitors in the array are derived by interconnecting multiple capacitors that match one of the unit capacitors. Die area is reduced while accuracy is maintained by controlling the larger unit capacitor with the least significant bit of the binary control word whenever possible and using the smaller unit capacitor only as a trim capacitor.
Claims11
A programmable analog cell, comprising:
- an active circuit;
- and
- a first programmable element coupled between a first node of the programmable analog cell and an input of the active circuit or between the input of the active circuit and an output of the active circuit, and including a first common plate and first and second passive elements that are switchably coupled between first and second terminals of the first programmable element, where the first passive element includes a single top plate continuous over a first portion of the first common plate and the second passive element includes a single top plate continuous over a second portion of the first common plate and where an area of the single top plate of the first passive element is unequal to an area of the single top plate of the second passive element.
A programmable element, comprising:
- a common plate;
- a first passive element including a top plate continuous over a first portion of the common plate, where the first passive element is switchably coupled between first and second terminals of the programmable element;
- and
- a second passive element including a top plate continuous over a second portion of the common plate, where the second passive element is switchably coupled between the first and second terminals of the programmable element and where an area of the top plate of the first passive element is unequal to an area of the top plate of the second passive element.
A method for programming a programmable analog cell, comprising the steps of:
- forming a conductive region;
- forming a first unit capacitor having a top plate that is continuous over a first portion of the conductive region;
- forming a second unit capacitor having a top plate that is continuous over a second portion of the conductive region, where the first and second portions of the conductive region are unequal;
- switchably coupling the first unit capacitor between first and second terminals of the programmable analog cell;
- and
- switchably coupling the second unit capacitor between the first and second terminals of the programmable analog cell.
A capacitor array having a first terminal and a second terminal, comprising:
- first and second unit capacitors coupled between the first and second terminals of the capacitor array;
- where the first and second unit capacitors each has a top plate that is continuously formed over a common plate;
- and
- where an area-to-perimeter ratio of the top plate of the first unit capacitor is unequal to an area-to-perimeter ratio of the top plate of the second unit capacitor.
Dependencies are inferred from the claim text.