Cheap mixed-signal ASIC as easy as FPGA - Embedded.com

Cheap mixed-signal ASIC as easy as FPGA

How will you make that complex analog/digital circuit in volume?

Traditionally one would lay out a board. Maybe all or most of the digital bits can be stuffed into a field-programmable gate array (FPGA). The analog generally gets distributed via op amps, transistors, and passive components over the printed-circuit board. Crank up the volume and it might make sense to ASIC-ize the FPGA, but there's not much one can do to compress the analog.

Triad Semiconductor now offers an intriguing solution, a mixed-signal ASIC that is relatively cheap to produce.

The company sells ICs they call Via Configurable Arrays (VCA), which are nearly-complete ASICs. They're composed of “tiles” that contain standard components, such as all sorts of op amps, resistors, capacitors, data converters, and the like.

These are mixed-signal parts so MCUs and memory are available on-chip as well, with a variety of common peripherals.

Triad's web site is a little frustrating to navigate, but this page lists the characteristics of the different VCAs. An IC with a Cortex M0 can have a few dozen op amps and gobs of digital circuits and programmable logic. Or a more analog-centric device (like their VCA-6) will have a couple of hundred op amps with gain-bandwidth products up to 50 MHz, 10,000 capacitors (!), nearly as make resistors, 2,500 transistors, over a megabit of static random-access memory, a couple of 200-MHz phase-locked loops, and a million logic gates. That could form one heck of a complex analog/digital circuit.Since the VCA is a standard component, only a single mask layer is needed to specify a user's design. VCA wafers are staged at the foundry (they are fabless and work with several production houses), awaiting the last mask layer.

The ViaASIC costs around $250k for the non-recurring engineering (NRE)–down from $1m typical full-ASIC costs–and speeds initial deliveries to 3 to 5 months. But most of those costs are engineering labor. Now the company offers ViaDesigner, a software tool that automates much of that effort, dropping the cost by better than an order of magnitude.

ViaDesignerViaDesigner is akin to the tools we use when working with FPGAs. It does schematic capture, supports Verilog and VHDL, and includes modeling and simulation components. SPICE and HDL modeling tools run side-by-side, helping the engineer get a correct design on the first spin of silicon. Wizards automatically generate a lot of the circuits; one can specify, for instance, a digital-to-analog converter's voltage output, clocking schemes, number of bits of resolution, etc, and the wizard will design the DAC. Or a filter: do you want high or low pass? Band pass or band stop? Which order? What sort of approximation algorithm? Fill in a form with these parameters and the tool does the rest.

The notion is pretty cool: design a mixed signal circuit as simply as putting an FPGA together. Keep costs low with a single-layer mask instead of a (hugely expensive) full-custom ASIC.

Triad tells me the these parts make a lot of financial sense for products in the 10K units of volume, but that that cost should eventually rival the price of a PCB.

Triad's web site is here: www.triadsemi.com. And they have launched a new website, www.ViaDesigner.com, where you can download your own copy of ViaDesigner and share mixed signal design questions and ideas.

Jack G. Ganssle is a lecturer and consultant on embedded development issues. He conducts seminars on embedded systems and helps companies with their embedded challenges. Contact him at . His website is .

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