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EDNE MARCH 2013

pulse Microchip turns tag into touch BodyCom technology is a way of using the human body as a secure, low-power communication channel, according to Microchip Technology. Bodycom uses a small, low-power module which you carry on your person. It does not have to be in close contact with the body, carrying it in a pocket is sufficient: but once carried, it enables you to make a “touch” contact with the other part of the BodyCom, a transceiver IC, via an electrode array. By analogy with an NFC tag system, the portable unit turns the user’s body into the tag, enabling a low-data-rate exchange (up to 10 kbit/sec) over a very short distance – a touch or proximity contact. You can use it to connect securely to a range of wireless applications, with bidirectional authentication for advanced encryption technologies. Applications can see extended battery life by eliminating the need for a wireless transceiver or high-power inductive fields. No RF antennas are required, and BodyCom offers simple circuit-level design through use of the BodyCom Development V1.0 Framework, which is supplied through free software libraries that work on all of Microchip’s PIC microcontrollers. BodyCom technology is activated by capacitively coupling to the human body. The system then begins communicating bidirectionally between a centralised controller and one or more wireless units. You can use the scheme, Microchip suggests, as the basis of a highly-secure channel with bidirectional authentication supporting advanced encryption, such as KeeLoq technology and AES. BodyCom technology helps to prevent the “Relay Attack” problem that is typical in automotive passive-keyless-entry security systems, Microchip adds. The list of possible uses is long, but includes keyless entry; enabling or disabling potentially harmful devices such as power tools (the product will only power-up when held by an authorised user); a similar solution for weapons; medical devices; or consumer electronics such as profile management for gaming consoles and exercise equipment. The “terminal” side of the transaction needs only to be equipped with a conductive array that can be touched by the user, similar to any touch-enabled device. The array can be shared with other touch applications; and transparent ITO (indium-tin-oxide) conductors work well. Therefore, any touch-screen device might have authentication added and would only respond to users who themselves carry a validating tag. Signals are conducted over the body (from touching finger to pocketed tag) at, Microchip says, picoAmp levels; antenna design is unnecessary, as the systems uses a low-frequency framework with a common microcontroller and standard AFE frequencies (125 kHz and 8 MHz), with no need for external crystals. BodyCom technology also eliminates the cost and complexity of certification because it complies with FCC Part 15-B for radiated emissions. More at www.microchip.com/get/GA5E Digitally enhanced power control Also recently new from Microchip is its digitally enhanced power analogue controller for DC/DC designs – an analogue-based power management controller with integrated MCU, for flexible power conversion; with matching 25-V MOSFETs. Designers of power conversion products who would like to gain the benefits – or at least, some of the benefits – of digital power techniques, without committing themselves to a full-scale digital power design exercise, are offered Microchip’s MCP19111. The part marries – on a single die – an analogue power regulator controller, along with a flash-based 8bit PIC microcontroller that carries out configuration, supervisory, reporting and control functions. The part operates from 4.5 to 32V. Microchip notes that many companies are reluctant to switch to digital power – that is, full digital power designs, where the regulatory control loop is carried out in the digital domain – because of the resource implications of requiring digital design techniques from groups who may not have that expertise. Microchip’s solution is to combine its analogue and logic circuitry experience in a single chip; the analogue portion comprises a peak-current regulator controller that drives external MOSFETs via a PWM (pulse-width modulation) generator. Key parameters that, in a fully-analogue part, would be set by external passive components, are controlled by selected values from on-chip switched-arrays of resistors and capacitors. Making that selection is firmware that runs on the associated 8-bit MCU core. The firmware comes with the part, and you set it up via a GUI; no programming is needed. The MCU core has multiple connections into the analogue control loop and can report key voltage and current level, set and monitor thresholds, and report faults over a serial connection. You do not have to write code for the MCU core, but there is capacity to run code if you choose to do so; a Microchip spokesman says that once the power-up configuration is done, the core “has not got much to do” – the computation load that would occupy a DSP or MCU core in a digital part is largely 8 EDN Europe | MARCH 2013 www.edn-europe.com


EDNE MARCH 2013
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