Today’s System on a Chip offer an astounding level of integration. Advanced processes like 28nm, 16/14nm and soon 10/4nm give designers billions of transistors to work with. SoCs can integrate multi-core processors, high speed interfaces, graphics subsystems and embedded memories.
However, even the most sophisticated and highly integrated SoC 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. 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 a fairly expensive addition to a bill of materials and is not a cost saving over discrete components. It is also an inadequate solution since an FPGA cannot address the entire external circuit, namely the analog or discrete components.
For IoT solutions, this issue will be even more pronounced as an MCU or SoC cannot address all of the possible sensor, power, and connectivity options. This is further complicated by the fact that any one IoT application will be much lower-volume 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 of 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 devices have to surrender valuable board 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. The concept of analog and digital FPGAs has been around a long time, Silego was the first company to truly think through the architecture, analog design and software issues. Silego 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. Included are:
- Asynchronous State Machines
- Timing Delays Counters
- Pulse Width Modulators
- Comparators
- Voltage Monitors
- Voltage References
- ADCs
- Glue Logic
- 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 the Silego 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. Some of the most popular are:
- Motor & Fan Control
- System Reset
- LED Control
- Over Voltage Protection
- Power Sequencing
- Voltage Detection
- Frequency Detection
- Sensor Interface
- Port Detection
- Temperature Control
These can be found in a wide variety of applications and markets, from mobile devices to wearables, industrial control and consumer audio.
Configurable Mixed-Signal ICs offer multiple advantages over traditional discretes and analog:
- Convenient, Faster Way to Prototype
- Optimized Board Space
- Lower-Cost Bill of Materials
- Confidential Design That Is Hard to Copy
- Less Complex and Less Stressful Supply Chain
Convenient, Faster Way to Prototype
Traditional circuit prototyping involves multiple time consuming steps:
- Circuit design
- Part selection
- Ordering samples and then waiting for the parts to arrive
- Laying out a board, hand assembly of sometimes dozens of parts
- Debug
- And repeat…..
This process can take many days if not weeks. Engineers don’t want to wait for parts to arrive or spend time doing tedious assembly. They want to get to work and get results quickly.
Prototyping with Configurable Mixed-Signal IC is much faster. Schematic capture, emulation and programming can be done in the same day. CMICs are very similar to FPGAs but with analog functionality. The CMIC process makes “what if” exploration easy as well. Changing a function is as easy as making the schematic change and programming a new part.
Optimized Board Space
A dozen or more components can take up precious real estate in any system. Today’s smartwatches, IoT devices, mobile phones, and ultra-thin laptops and tablets can’t spare any board space.
A Configurable Mixed-Signal IC can integrate several components into one tiny product. Depending on the functions supported, these range in size from 8 pin 1.0×1.2mm to 20 pin 2.0×3.0 STQFN packages.
Board savings will depend most importantly on the type and number of functions implemented. Customers have seen space reductions of 60-90% by integrating 12-30 components or more. For this reason, designers of wearable devices are especially enthusiastic users of Configurable Mixed-Signal ICs.
Lower-Cost Bill of Materials
It is easy to see how a Configurable Mixed-Signal IC allows for an easier design process and faster development. It is also easy to see how valuable board space can be saved by using CMICs. However, unlike traditional FPGAs, Configurable Mixed-Signal ICs don’t offer these benefits at a price premium. 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 1 CMIC part replaced $1.50 of level shift and comparator circuitry with a single $0.35 CMIC. This CMIC delivered significant savings with an opportunity to include even more functionality with its unused resources. There are several reasons for the relative cost effectiveness of CMICs:
- The One Time Programmable NVM is very cost efficient
- CMICs are designed and fabricated in a single process node that is a sweet spot for die size, analog performance, digital density and cost per layer and assembled in a single packaging technology.
- Analog components and discretes are priced relatively high on a per-function basis.
- The suppliers of analog and discrete components are not motivated to reduce or improve their low ASP product cost structure. For many of them it would require going fabless or redesigning.
A Confidential Design That Is Hard to Copy
A discrete circuit with standard off the shelf components is easy to copy or clone. A CMIC design is unique to the customer who designed it. This makes it very difficult to copy or reverse engineer. This helps designers of consumer products maintain a competitive advantage where there might be dozens of would-be competitors looking to knock off their innovative designs. 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.
Less Complex and Less Stressful Supply Chain
An important effect of avoiding or integrating multiple components is reduced complexity for a supply chain. Fewer parts to qualify, fewer to order, fewer to inventory; all of these factors have positive bottom line impacts. By reducing multiple parts, the risk of being in allocation or not being able to get a particular component device is reduced. It only takes a single discrete transistor to go on allocation or end of life to bring a line down or cause other serious issues.
CMICs offer many benefits that will make designers’ work easier and their products more profitable. They are the ideal solution when board space is tight or needs to be maximized to save space for other valuable functions (such as a bigger battery). They also make procurement happy by saving significantly over traditional analog and discrete while dramatically reducing the risk and stress involved. So while SoCs are not truly SoCs, the next best thing is an SoC with a CMIC.