Programmable analogue makes a resurgence 2014

Description:

Some of the earliest computers used for controlling processes featured analogue architectures because they were much more responsive than valve based logic circuits. But they needed to be custom designed and succumbed to the more flexible – and ultimately cheaper – digital computer.

However, advances in programmable analogue technology may see not just the resurgence of analogue computing in areas where digital works out to be more power hungry, but also a way of supporting analogue functions on increasingly dense but highly variable SoCs.

Although switched capacitor circuitry is a good match for CMOS, switching imposes a limit on the achievable bandwidth of the circuit. Continuous time architectures can, in principle, process higher frequency signals. Zetex' TRAC architecture achieved bandwidths more than an order of magnitude higher than its switched capacitor peers in the late 1990s and early 2000s. One architecture developed at the University of Freiburg in the last five years, has achieved unity gain of close to 200MHz. 



The recognition that most analogue circuitry now drives a digital core has led to the appearance of devices such as Cypress Semiconductor's PSoC and, more recently, Maxim Integrated's MAX11300. These put a series of analogue building blocks onto a digital chip. In the case of the PSoC, analogue functions are under the control of an on chip microcontroller. The Maxim part, meanwhile, is configured at design time to link different mixed signal elements such as A/D and D/A converters together directly.