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Analog counterparts of FPGAs ease system design
Abstract
Electronically Programmed Analog Circuits (EPACs) are the answer to need for low-cost, easy-to-use, foolproof analog ASIC, and counterparts to the digital designer's field-programmable gate array (FPGA). These are analog ICs which have functionality, performance and connectivity programmed by the user or even by a host microprocessor or microcontroller. With the 50E10, the first EPAC, costs are lowered, functional-block level design is easily modifiable, loading or stability problems are detected and corrected, and control of system dynamic range is achieved by summing input of programmable-gain module. It also provides group switching input signals to different group inputs to create unique signal conditioning for each input. Though the 50E10 is aimed at general-purpose signal-conditioning tasks in medical, industrial, or other instrumentation and control system, future EPAC will target such tasks as data acquisition, running control loops, and providing systems scan-test capability.
... Switched-Capacitor FPAA. In 1994, IMP Inc. introduced the 50E10 Programmable Analog Signal Conditioning Circuit (Fig. 15), the ®rst IC in their series of Electrically Programmable Analog Circuit (EPAC) devices [13,32,77]. Aimed at multi-channel analog signal conditioning applications that require channel-dependent signal scaling and offsets, the 50E10 has an analog multiplexer front end, variable offset and gain modules, a summing ampli®er and output blocks that can be con®gured as comparators, ampli®ers or sample and hold circuits. ...
The drive towards shorter design cycles for analog integrated circuits has given impetus to several developments in the area of Field-Programmable Analog Arrays (FPAAs). Various approaches have been taken in implementing structural and parametric programmability of analog circuits. Recent extensions of this work have married FPAAs to their digital counterparts (FPGAs) along with data conversion interfaces, to form Field-Programmable Mixed-Signal Arrays (FPMAs). This survey paper reviews work to date in the area of programmable analog and mixed-signal circuits. The body of work reviewed includes university and industrial research, commercial products and patents. A time-line of important achievements in the area is drawn, the status of various activities is summarized, and some directions for future research are suggested.
A novel field-programmable analog array (FPAA) architecture based on switched-capacitor techniques is proposed. Each configurable analog block (CAB) in the proposed architecture is an opamp with feedback switches which are controlled by configuration bits. Interconnection networks are used to connect programmable capacitor arrays (PCAs) and the CABs. The routing switches in the interconnection networks not only function as interconnection elements but also switches for the charge transfer required in switched-capacitor circuits. This scheme minimizes the number of connecting switches between CABs and PCAs, thereby, it reduces the settling time of the resultant SC circuits and thus achieving high speed operation. The architecture is highly flexible and provides for the implementation of various A/D and D/A converters when the FPAA is connected with external digital circuits or field-programmable gate arrays (FPGAs).
This paper presents a variety of applications of an FPAA based on a regular pattern of signal-processing cells and primarily local signal interconnections. Despite the limitations introduced by local interconnections, the presented architecture accommodates a wide variety of linear and nonlinear circuits found in many signal processing systems. Thus it effectively proves that it is possible to improve the performance of an FPAA by means of constraining the interconnection pattern, without significantly limiting the class of circuits it can implement.
The design of a high-frequency field-programmable analog array (FPAA) is presented. The FPAA is based on a regular pattern of cells interconnected locally for high frequency performance. No switches of any kind are used in the signal path of a cell: programming of the functions, parameters, and interconnections is achieved solely by modifying cells'' bias conditions digitally. Limited global signal interconnections are also available for those application circuits which cannot be mapped onto locally-only interconnected structure. Key circuits of the FPAA have been fabricated in a CPI transistor-array bipolar technology.
A reconfigurable analog integrated circuit architecture based on
switched-capacitor techniques is proposed. The architecture consists of
an array of opamps and programmable capacitor arrays (PCAs)
interconnected by an interconnection network. The routing switches in
the interconnection networks not only function as interconnection
switches but also switches for charge transfer. This scheme minimizes
the number of routing switches and the settling time of the embedded
circuits. The architecture is also highly flexible and allows the
implementation of various circuits including different types of data
converters
An electronically-programmable analog circuit (EPAC), based on the
switched-capacitor (SC) technique, is an analog counterpart of digital
FPGAs. The full speed potential of analog circuits, however, can be
utilized only by continuous-time (CT) field-programmable analog arrays
(FPAAs). In this paper an example of an FPAA structure with local
interconnections is shown. Each cell derives a weighted sum of selected
signals from four nearest neighbors, and optionally performs integration
(ideal or lossy) to produce its own output signal
The development of accurate, low-cost, rapid prototyping
techniques for analog circuits has been attempted at various times using
variety of implementation formats over the past several decades with
varying degrees of success. Commercial products introduced recently,
along with progress made at University research labs, indicates renewed
interest and further accomplishment in achieving this goal. This paper
reviews past work in the area from both universities and industry,
provides a status report on the state of activities world-wide, and
attempts to forecast developments in prototyping analog and mixed-signal
systems one can expect in the near future
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