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Reference designs help simplify a designer's work, but could they go a few steps further?

Reference designs are becoming increasingly valuable in terms saving development time. Traditionally, these references were particularly useful at the 'proof of concept' stage, but tended to be too over specified and cumbersome to be used in the final design.

On top of that, concedes John Jones, technical marketing manager for distributor Avnet Memec, not all suppliers are necessarily that good at making development or evaluation kits. On those occasions, Avnet Memec would sometimes step in and design a reference itself, assuming the volume potential was there.

However, the company has recently aligned its business model to cater for the Internet of Things which, obviously, has connectivity at its heart and this encourages the use of reference designs. Jones commented: "There are a lot more challenges when you connect things. If it is a wireless connection, there is interoperability so, for Bluetooth, you need to go to the Bluetooth SIG and get approvals and that is before you get to CE approvals and type approvals. That is where people need – and almost expect – a reference design."

Such references traditionally come from suppliers, but Avnet Memec realised it was in an ideal position to provide more integrated solutions by bringing suppliers together. "CSR, for example, does its own reference designs. But if it wants to catch the attention of, for example, a MEMS supplier and then a power management supplier and then a battery supplier, get their support and then invest in the reference design itself, it is expensive and time consuming," said Jones. "But we can bring suppliers together, share funding of the reference design between the various partners and undertake in house any further integration that needs to be done. It is much more efficient."

One early example is the Avnet Memec designed Powerhouse – a plug-and-play module forming part of a new energy monitoring reference platform. Accurate energy measurement from Powerhouse is achieved by the inclusion of a high resolution analogue front end (AFE) from Cirrus Logic, based on a 24bit A/D converter. The CS5490 AFE is a preprogrammed power calculation core that provides active, reactive and apparent power, as well as power factor and instantaneous or RMS voltage and current. It uses a minimal number of devices for repeating in order to compute the most efficient path for each packet to reach its final destination, making it suited to building control applications. Powerline communication is supplied by Echelon's PLC system. Additionally, the smart transceiver includes self installation functions to eliminate the need for installation tools in those devices aimed at the consumer market.

This high level of integration of measurement, control and communication functions has brought a compact form factor that would not have been possible using individual reference designs, enabling the device to fit in a standard wall power socket. Plug and play functionality is achieved by the inclusion of Interoperable Self-Installation (ISI) from Echelon, enabling Powerhouse to address growing demand for real-time energy monitoring in home appliance, utility sub-metering, DIN rail modules and building automation applications.

This particular reference design was unusual in that its design was partly conducted by a customer, rather than by the lead suppliers, which is the norm.

Another example is an energy harvesting reference design. The core supplier was Maxim, which had the controller to manage the power. Jones commented: "We bought in the other suppliers from our line card or from other Avnet companies – we didn't have a battery company, for example, so we called on Avnet Abacus – and so we could bring the whole bill of materials together."

Of course, the bottom line is that Avnet Memec stands to get more components on its customers' BOMs if they have been used successfully on an integrated reference design. However, the company's focus on IoT solutions lends itself to this approach. Jones commented: "We may have been successful with a key part – the MCU – but have not managed to sell the power management or the connectivity piece. If we go to the rest of the customer base with a reference design, it increases our chance of getting the connectivity and the power management components, along with the MCU. If we make it really easy for our customers, then we are more likely to get more of the BOM."

The key aspect is the company's knowledge of its supplier's components, along with its own integration capabilities, allows it to provide integrated solutions – working and optimised – that save the customer time. "By doing the design, we are simplifying things for customers," said Jones. "They can 'cut and paste' and get to market quickly. We are saving money for our customers and for our suppliers."

Designing with NFC
SmarTool NFC is a reference design board created to help customers develop hardware and software that uses Near Field Communication (NFC) technology for applications such as access control, payment systems and contactless data exchange. The board was developed jointly by Arrow's European engineering team and NXP Semiconductors.

David Spragg, VP Semiconductor Engineering, Arrow EMEA, said: "NFC standards, which have achieved widespread adoption in smartphones and passenger transit payment systems, are now being designed into a wide range of other applications. In developing SmarTool NFC, our aim was to speed the development of these new systems by providing a simple and effective path to NFC deployment."

The SmarTool NFC main board includes an NXP PN532 transceiver for contactless communication; an NXP LPC11U37 MCU that supports full speed USB 2.0; a step down DC/DC converter; ultra low jitter clock; and an LCD. The MCU is based around a 50MHz ARM Cortex-M0 core and features a 128kbyte flash memory and 12kbyte of RAM.
The reference design is supplied with a set of ready made application software that demonstrates the implementation of NFC technology in areas such as access control and micropayment.

Under access control, the system interacts with a mobile phone or an NFC tag and registers the presence of an enabled device. In the micropayment application, the system simulates a vending machine and allows money to be loaded and products dispensed. The software is compatible with devices using NXP MIFARE smartcard ICs including Classic, Ultralight and DESFire.

An additional application is supplied to assist antenna calibration. It provides an alternative to measuring parameters when users do not have access to specialist analysers. Using this method, a frequency generator feeds the antenna with a sweep around the desired resonance frequency. At the same time, the MCU generates an analogue signal proportional to the output frequency. By connecting two scope probes to the ramp generated by the MUC and to the antenna and setting the scope to XY mode, the user can see the resonance frequency profile of the antenna. This will then aid the tuning process.

Tim Fryer

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