An Adaptive Circuits Concept
Original Publication Date: 2003-Apr-16
Included in the Prior Art Database: 2003-Apr-16
The “Adaptive Circuits Concept (ACC)” presented in this paper is an alternative to reliance on specialized process technologies for achieving tight matching requirements by embedding small, quiet, adaptive digital circuits within analog chips. Matching requirements may originate from an analog RF/IF application (e.g. for minimized undesired inter-modulation) or a digital application (e.g. RC delay matching to avoid clock/data skew). In such cases, our adaptive circuitry can provide precision matching. To be practical, however, penalties in power, chip area, noise, circuitry speed, design time, etc., must be minimized. Our approach described herein achieves these objectives, by use of exact digital storage (registers and non-volatile memory) for error correcting values and surprisingly simple ‘mismatch sensors’ that require no external hardware. We envision highly reusable, adaptive, components being a standard part of a design library, just as resistors and capacitors are today. Many ‘formerly analog’ circuits have been replaced by digital implementations to attain higher performance, lower cost, and improved yield (e.g. by eliminating mismatch and bias issues). However, most RF circuits, and some IF circuits, still operate at too high a frequency for power-efficient, all-digital implementations. It is still possible to utilize digital circuit advantages to improve RF (as well as IF and general analog) circuits. For example, digital registers can store, and later recall, extremely precise values with zero error. Also, software can rapidly perform extremely sophisticated operations on those digital register values. The result can be used to adjust/compensate/adapt the analog RF circuits that would otherwise suffer from the typical analog problems (e.g. mismatch and bias problems). This ability to adapt circuits, after they are packaged or in the field, enables design tradeoffs between performance, area and cost. Previously, customized designs of digital programming/trimming techniques have been reported. However, completing each custom implementation is a daunting task, with little or no potential for re-use. A reusable, unifying method for implementing adaptive circuits is needed. This is the underlying principal of the ACC concept.