Near field communications (NFC) is a standardised short range radio link that builds on the well established technology of RFID tagsand is now being used in mobile phones and an increasing range of consumer applications.One way this can be integrated cost-effectively in mass-market electronic devices is through System on Chip (SoC) implementation in other common chipsetsincluding those for BluetoothWiFi and UWB. In high-volume productsSoC implementation of NFC offers significant unit-cost savings and very efficient integrationwith lower overall spaceprocessing and power requirements – while adding great value.
Integration is an established ‘fact of life’ in the consumer electronics product lifecycle. Usuallythe first products to market are built from discrete componentsand their typically high sale price reflects the high production costs and small production volumes. As a product becomes more popular and successfulmanufacturers can begin to invest in progressively greater integration of components to drive down manufacturing costs as volumes increase.
In consumer electronic devicesintegration of a new technologies follows a well-trodden path. When a new technology comes alongthe first products might be external devices that can be connected via a cable tosaya PCdigital camera or mobile phone. Next there are card accessories that can be plugged into the PC or phone. Then comes a chipset that sits on the motherboard. And finally there could be even closer integration of the technology with other functionality on the motherboardwhere this makes technical and economic sense.
Technologies undergo a similar process of integration within the devices themselvesof course. A prime example is the development of the GSM mobile phone from single-band (900MHz) only operationthrough multi-band GSM (900MHz1800MHz1900MHz) operation to multi-mode (GSM/WCDMA) operation. As these new capabilities were introducedmulti-band and multi-mode blocks were typically added for the digital logic and signal processing parts.
Initiallyhoweverthe different RF parts were implemented as separate blocksas digital logic and RF technology were developing at different ratesand market demand for the different combinations of RF bands was not well established. TodayRF design and market acceptance have moved on to the point where the RF part is common for all frequenciesand even the previously separate antennas for the different bands have become integrated into one planar design. In other wordsover timeit has become possible to move commonality further down the mobile phone functionality stack.
The key issue facing electronic product designers and manufacturers is whereand how closelyNFC should be integrated into their products. When to integrate NFC with other technologiesand which interfaces to provide to the host systemare key considerations. Integrate too earlyand you could have an expensive white elephant on your hands that proves difficult to update in line with changing market demands. Integrate too late and you could be left behind in the race to meet volume demand from a mass market cost-effectively.
The choice of interface point is a key market success factorespecially when different technologies are developing at different speeds. If integration is performed with interfaces at the wrong point – with stable technologies integrated with less mature ones – adding or developing capabilities on the ‘integrated’ side of the divide could become much more costly than if they had been left on the other side of the interface.
The integration point shifts with time and changing market conditions. The trick is to know when to move to the next level of integration.
NFC integration
As with other technologiesNFC is going through a classic integration process. The first prototype implementations of NFC in mobile phones were as cover units that clipped on to the back of the phone – analogous to a plug-in line card. While these devices were useful for accessing and testing the market for NFC-enabled mobile phonesthey were unlikely to take off as a mass-market consumer productas the NFC covers cost about the same for 10000 units as complete phones cost for 10million units. Nowas NFC moves to the next level of integrationdesigners have the choice of developing NFC chipsets to sit on electronic device motherboardsor moving to SoC implementations.
The benefit of greater integration is a significant cost benefit in high-volume productionwhich should more than cover the up-front design and development costs. But before jumping in and choosing one route or anotherdesigners and engineers should consider what role NFC will play in the deviceand whether there are ‘overlap’ areas with other circuitry on the host device’s existing silicon.
So is there circuitry already available on the typical electronic device motherboard for NFC to ‘piggy-back’ on to? Like any RF-based technology todayNFC requires a certain amount of analogue circuitry for transmitting and receiving analogue radio waves. Around 99percent of silicon today is purely digital (mostly memory)and there is little scope for building extra processes on this. But luckilythere are several areas of combined digital/analogue circuitry in devices like mobile phonesPDAsdigital cameras and payment terminalswhich provide ideal hosts for NFC processes. Chief among these are BluetoothWiFi and UWB chipsetsand there are several other candidates.
Using such hosts for SoC implementations of NFC makes a lot of sense financially. The additional cost of including a stand-alone NFC chipset on the typical electronic device motherboard can be US$3-5 per unitand requires 25–30 connector pins. Implementing the same NFC functionality as a custom IP block on a Bluetooth chipset typically adds much less than US$1.00 per unit (and only a few tens of cents in sufficient volumes)requires only 6–8 connector pins (including test pins) andobviouslyneeds no separate chip. The NFC IP block can be placed in the corner of the Bluetooth chipset using on-chip connections.
The financial attractions of SoC are clear when addressing a mass market. Of coursethere are up-front costs for developing custom IP for SoC implementationsbut these will quickly be repaid through bill of materials and production savings in high volumes. When one considers that there are 300million Bluetooth chipsets sold annuallythe time taken to recoup even a US$1million development investment would not be significant if the manufacturer can charge an extra US$0.50 per unit for built-in NFC capability.
The reduction in pin connectors is also significant. In electronic devices like mobile phonesdigital cameras and payment terminalsmotherboard 'real estate' is very limited and expensive.
Integrating NFC with BluetoothWiFi or UWB chipsets also makes a lot of sense from a technical perspective. Many of the processes and components needed by these RF-based technologies are the same: antennapowerclockdata busto name a few. Having the NFC IP block on-chip also avoids the need for it to have its own ESD protection and drivers to ensure it works over the distances involved.
As with its host chipsetNFC can be implemented as a ‘clever peripheral’ with its own microprocessorso that it does not need to wake up the main processor each time there is NFC activity – only when ‘real’ data is passed does the host processor get involved. What is more it means the NFC element avoids becoming part of the main device development programme.
Design and implementation issues
The choice between a custom IP block for SoC and a custom chip implementation is determined by the emphasis of the project – whether it is on memorysizepower requirementfor example – or if additional functionality is required for an existing SoC.
For exampleto add NFC capability to a Bluetooth SoCthe challenges stem from the fact that different semiconductor vendors use different SoC design practices and procedures. Some emphasise memory optimisation; others focus on sizelayout or power consumption. Providing an NFC IP block that is optimised for use across these different environments requires extensive experience of the fab industry toolseach vendor’s proceduresan in-depth understanding of the customer requirements and design-flow.
The design-flow starts with the specificationand then moves on to architecturecomprising both analogue and digital elements. Successfully combining both elements into a customised solution requires highly specialised expertise in both analogue and digital design.
Once the analogue and digital components of the design have been integratedthis element of the design can be fed back into the specification to enable productisation.
Assuming there is sufficient volume to justify the development costscustom IC design – whether for stand-alone or SoC implementations – offers the advantage of enabling the designer to focus on meeting customer requirements in a way that cannot be achieved using standard products.
In a nutshellcustom IC design optimises the cost of IP ownership and – as it is tailored specifically for purpose – it contains exclusively non-recurrent engineering. This means that for a given applicationpower usagesilicon area and memory can be optimised to a specific requirement. Using custom IC design for NFC SoC implementations also means the host chipset designers do not need to become experts in a new area.
Typical implementations of custom IC design for NFC would be for mobile handsetssmart posterssmart business cardsand consumer electronics.
As NFC becomes more widely adopted as a mass-market technologythe advantages of SoC implementations become more compelling. Bluetooth chipset manufacturers have already shown that bluetooth/FM integration provides a successful business model in the mobile phone market. If anythingthe business case for Bluetooth/NFC integration is even betteracross a boarder range of applications - and this model applies equally well to other chipsets.
Designing and implementing NFC SoC circuitry requires detailed knowledge and experience. Mistakes or late changes in the design of a bluetooth or WiFi chipset could cost hundreds of thousands of dollars to put right. Chipset manufacturers are now implementing NFC in a number of different ways toprovide this integration.
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