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EDNE MAY 2014

by Colin Dugan and Denis Labrecque, Analog Devices Analogue components plus ARM MCU cores to met embeded challenges The design of tomorrow’s embedded systems presents complex challenges given the aggressive goals of improvement in areas of performance, cost, power, size, new features, and efficiency. An emerging design option to address these complex problems lies in analogue components intelligently integrated with ARM microcontroller cores. Smart integration of high performance analogue components (amplifiers, ADCs, DACs, voltage references, temperature sensors, wireless transceivers etc.) and 32 bit processor cores from ARM with the right digital peripherals can address goals that discrete solutions cannot. In order to create the optimum analogue microcontroller solution, a strong knowledge of the overall system along with the availability of the right intellectual property (IP), and expertise in that intellectual property, is required. Chip designers and system engineers specifying the features of these integrated devices must have an exceptional understanding of the end application requirements. This domain knowledge is critical and includes a solid understanding of board level requirements such as form factor, temperature ranges, manufacturing, power consumption, cost, and complementary components in the signal chain. Availability of the right IP provides a strong starting point for meeting system level goals. This starting point is needed to keep the development period of the analogue microcontroller short. Increasingly, the acquisition/ creation and implementation of the IP itself, Figure 1. Block diagram of two stage solar PV inverter system; area in red shows blocks targeted for smart integration. appropriate for the application, needs to be facilitated by the semiconductor manufacturer. This IP then needs to be modified to meet two requirements, in particular. The first is to maximise system level benefits by optimising performance and operation based on the needs of the primary target application. The next is to optimise the IP to work very well and very easily with the other complementary IP blocks in the analogue microcontroller. And finally, there needs to be the opportunity at a business level for collaboration, combining the expertise and knowledge of the system manufacturer and semiconductor manufacturer resulting in an optimised, unique design. Analogue MCU applications There are many applications that can benefit from a device that integrates high performance analogue with ARM microcontrollers including temperature sensing, pressure sensing, gas detection, solar inverters, motor control, health care vital signs monitoring, automotive monitoring systems, and gas/water/ electric meters. This article will look at two applications areas where integration of optimised high performance analogue and ARM microcontroller cores leads to significant benefits in cost, power, size, and performance: 1) Inverters for solar photovoltaic systems (PV) with goals of increased efficiency, bill of material (BOM) cost reduction, and integration of intelligence to support interfacing to the smart grid. 2) Motor Control, with the goals of improved efficiency for environmental benefits and cost reduction. Note that while these smartly integrated mixed signal devices are optimised for particular end-applications, they can also work well for numerous adjacent applications having similar functional requirements to the primary target application. Solar photovoltaic inverters: : context - cost reduction, and the smart grid To better compete against traditional energy sources such as natural gas, coal, and oil, cost reductions of solar PV generated electricity is best achieved by both increases in efficiency and reduction in system BOM costs. As cost/efficiency of the panels themselves is trending down, new technologies also promise advances for solar PV inverters - the interface between the power generated by a solar panel and the grid. These new technologies include NPC topologies 3 level/ 5 level / multilevel, and high frequency switching topologies using fast power transistors based on silicon carbide (SiC) and gallium nitride (GaN) materials. Figure 1 shows a two stage solar PV inverter system. Power from the panels, essentially a DC source, is converted to AC for the grid. The first stage is a DC to DC conversion that raises the voltage level so it is compatible with the peak voltage on the grid. The second stage is a DC to AC conversion. The area in red shows the low voltage circuit control components that, when integrated into a single analogue microcontroller chip, give benefits at a system level. The authors continue the expanded version of this introduction by looking in more detail at the level of performance required of the analogue blocks in this mixed-signal scenario. Complete article, here www.edn-europe.com EDN Europe | MAY 2014 25


EDNE MAY 2014
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