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DESIGN & PRODUCTS ANALOG & MIXED SIGNAL Optimizing embedded designs with configurable mixed-signal ICs and asynchronous state machines By Michael Noonen Systems on a Chip for embedded devices offer an astounding level of integration. Advanced processes give SoC and MCU developers plenty of transistors to work with. These devices can integrate multi-core processors, wireless connectivity, memory as well as graphics controllers. However, even the most sophisticated and highly integrated SoC or MCU requires some external circuitry for power management, human interface or connecting to sensors. As a result, there are almost always comparators, op amps, level shifters, various logic and discrete transistors scattered across a design. These SoCs are almost never truly Systems on a Chip. In some cases, the support logic needed can be swept up into a low-end FPGA. But usually this is not a cost saving over discrete components. It is also an inadequate solution since an FPGA cannot address the analog or discrete components. For an embedded device, this challenge will be even more pronounced as an MCU or SoC cannot address all the possible sensor, power, and connectivity options. This is further complicated by the fact that any one embedded device will be much lowervolume Silego’s GreenPack CMICs. than an SoC for a mobile phone application. Therefore, a typical MCU or SoC vendor will not be justified in spending the large sums needed to design and fabricate a device to support all the necessary permutations and integrate the required surrounding support circuitry. So, are designers forced to put up with sub-optimal designs with stray logic, overpriced analog and space-consuming discretes? Will the next generation of embedded devices surrender valuable space and be burdened by a bloated bill of materials? The answer is happily “No”, thanks to the emergence of Configurable Mixed-Signal ICs (CMICs). These devices are a clever matrix of analog and digital circuit functions that are configurable through One-Time-Programmable (OTP) Non-Volatile Memory. The pioneer and leader of this new category of devices is Silego Technology who introduced CMICs in 2009. Since then, Silego has completed over 1,300 customer designs and shipped over 2 billion configurable devices. Silego’s CMICs offer a variety of analog and digital resources that a designer can configure into mixed-signal circuits. These include asynchronous state machines, timing delays counters, pulse width modulators, comparators, voltage monitors, voltage references, ADCs, glue logic and level shifters. Designers can drag and drop these resources and “wire up” their design in a schematic capture tool, or they can emulate the design with Silego’s hardware development kit. When they are satisfied with the design, they can program the CMIC device with the on-board OTP memory. CMICs can be used for a variety of essential mixed-signal functions ranging from motor and fan control, to sensor interfaces and power sequencing. Cost and space savings Replacing traditional discretes and analog, configurable mixedsignal ICs offer multiple benefits to embedded designers and manufacturers. While a dozen or more components can take up precious space which could be better used for a larger battery or a slimmer form factor, a CMIC can integrate several components into one tiny package ranging from 8-pin 1.0x1.2mm to 20-pin 2.0x3.0 STQFN footprint. Traditional circuit prototyping requires days if not weeks to design a PCB, order components, fabricate the board, assemble, debug and repeat. In comparison, prototyping with a CMIC is much faster. Schematic capture, emulation and programming can be done in the same day. Changing a function is as easy as making the schematic change and programming a new part. CMICs have been designed to reduce the bill of materials cost over discrete and analog components in most situations. A recent design profiled on embedded.com highlighted that one single $0.35 CMIC part replaced $1.50 of level shift and comparator circuitry. Finally a discrete circuit with standard off the shelf components is easy to copy or clone. The CMIC circuitry inside is as secure as a full custom IC and only the designer or its designated ODM and supply chain partners can procure it. When designing portable systems, size and battery life constraints are often the most severe challenges to overcome. One traditional way to pack a lot of functionality into a small size and power budget is to use a low power microcontroller such as TI’s popular MSP430. These types of ultra-low power microcontrollers offer high levels of flexibility and are available in small packages. Silego Technology has taken a different approach in attacking this same problem, by adding a user programmable Asynchronous State Machine (ASM) macrocell to its fifth generation GreenPAK CMIC product family. The following comparisons illustrate design tradeoffs and tips that the user may consider when choosing between a variety of microcontroller options, and doing the same job using an ASM like the one inside a CMIC. Handling MCU code The CMIC’s Asynchronous State Machine contains 8 states and 24 possible decisions. The ASM represents an MCU program with up to 24 IF..THEN statements. When the 8 State ASM capabilities are considered together with hardware input and output circuits, the CMIC may be represented as being roughly Michael Noonen is VP Sales and Business Development at Silego Technology – www.silego.com. He can be reached at mnoonen@silego.com 26 Electronic Engineering Times Europe March 2017 www.electronics-eetimes.com


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