Motorola and Zetex take centre stage with FPAAs

Motorola and Zetex take centre stage with FPAAsOver the next three pages Steve Bush previews the annual showcase for Asics, FPGAs and EDA tools the Silicon Design Show taking place at Olympia 2 in London on September 17-18
Two manufacturers, Zetex and Motorola, are showing their field programmable analogue arrays (FPAAs) at the Silicon Design Show and both have recently induced development packages to go with their products.
Zetex, through its subsidiary Fast Analog Solutions (FAS) is promoting its ‘totally reconfigurable analogue circuit, or TRAC. This is a 20 cell device where each cell can be configured as one of seven analogue functions including log, rectify and add.
The TRAC development system consists of an evaluation board and a software package. The software allows users to drag and drop icons representing the functional options onto the cells to programme them. Macros, pre designed blocks of cells, can be moved around and stored for later use.
A simulator, with outputs in graphical and tabular form, predicts circuit performance and Zetex claims that this closely follow the performance of programmed actual devices. The development board allows completed designs to be tested on real hardware.
Motorola’s development system, like Zetex’s, consists of a board for hardware development and a Windows-based software design package. The board is called the MPAA3DS and the package is called EasyAnalog – not to be confused with Micrel’s analogue ASIC design package called EZ-Analog.
EasyAnalog offers similar facilities to the Zetex software, although simulation is not as comprehensive. The hardware evaluation board has a wire-wrap area for prototyping and several I/O connector options. Included is a four-pole 200kHz anti-aliasing filter for high frequency inputs.
Although they both have 20 cells, the Zetex and Motorola designs differ in architecture. TRAC has two 10 cell strings where all nodes are available and cells can be turned off to split the strings.
Motorola has a four by five matrix with multi-way switches controlling interconnection. Motorola’s I/O is through 13 nodes which each contain an opamp for signal conditioning.
Zetex’s cells are continuous-time analogue blocks with a bandwidth of 4MHz (20mV p-p input). This contrasts with the Motorola cell (Originally developed by Pilkington in the UK) which is a switched capacitor type, offering 200kHz maximum recommended frequency (500kHz Nyquist). On the other hand, the Motorola cell offer control over gain (1/20 to 20) and frequency response without the use of external resistors and capacitors.
In general, the Zetex part seems to be better suited to implementing non-linear functions like multipliers, whereas the Motorola FPAA seems to be better suited to creating reconfigurable filters.
Both companies offer design examples, with Motorola including a number of two-cell macros including a Schmidt trigger, biquad filter and sinewave oscillator.

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