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SILICON SILIC CHIP www.siliconchip.com.au Editor Emeritus Leo Simpson, B.Bus., FAICD Publisher/Editor Nicholas Vinen Technical Editor John Clarke, B.E.(Elec.) Technical Staff Jim Rowe, B.A., B.Sc Bao Smith, B.Sc Tim Blythman, B.E., B.Sc Technical Contributor Duraid Madina, B.Sc, M.Sc, PhD Art Director & Production Manager Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Dave Thompson David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Ian Batty Cartoonist Brendan Akhurst Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates: $105.00 per year, post paid, in Australia. For overseas rates, see our website or email silicon<at>siliconchip.com.au Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 * Recommended & maximum price only. Printing and Distribution: Editorial Viewpoint It’s getting hard to avoid tiny SMDs One of the challenges of planning content for SILICON CHIP is trying to maintain a good mix of projects. We need simple ones for beginners, more complex projects for advanced constructors, plus some designs of intermediate complexity. And then we need to publish some with micros and some with analog circuitry only, as some people love micros and others hate them. Then we have to consider the construction techniques used in each case. Do we stick with all through-hole components, use all SMDs instead, or some combination of the two? Where possible, we prefer to use commonly available through-hole parts, because that’s what the majority of readers are used to. But in some cases, we need to use surface-mounting devices (SMDs) instead. Their compactness allows us to design smaller, more feature-packed boards. But probably the most crucial advantage of designing with SMDs is the much broader range of parts to choose from. No doubt some through-hole parts will be available for decades to come, but many newer parts (especially ICs) are not being released in through-hole packages at all. So if we want to use modern parts, we have to include at least some SMDs in our designs. Take the world-leading DAB+/FM/AM Radio project in this issue. It is based around an Si4689 digital radio IC which is only available in a tiny 48pin QFN SMD package. It doesn’t even have any leads – just pads under the chip. That’s ideal for commercially assembled boards using infrared solder reflow, as the result is exceptionally compact. But it makes the chip difficult to solder by hand. But to build a radio which can tune into DAB+, FM and AM broadcasts, we had no other realistic choices. While soldering this chip can be a challenge, you don’t need expensive tools to do so. A low-cost hot-air reflow rig (available for less than $50) plus a syringe of solder paste and a steady hand is enough to do the job. That’s how we built our first prototype, and it worked fine. It isn’t just the main chip, either. To get good performance out of a radio chip like this, you must keep the critical components very close to the main IC. The only realistic way to do this is to use small SMD components, including tiny passives. The good news is we are planning to offer a limited run of PCBs with the QFN chip already soldered, for those who want to build the radio but don’t think they can solder the QFN chip. We are also thinking about offering boards with both the QFN chip and the surrounding small passive components already in place. There are numerous other SMDs on the board, but most of them are much easier to solder than the main chip and the parts immediately surrounding it. So building the radio will still be much easier. Maintaining a good mix of projects As I noted above, I realise that we need to publish a range of different electronic projects to keep all of our readers happy. But lately, we have published quite a few microcontroller-based projects and not so many analog or discrete designs. I love analog designs, especially audio circuits and power supplies. I think that some of my best design work has been in the analog realm. So we will be addressing that imbalance over the next few issues. You can expect to see more analog and discrete designs in the magazine in coming months. Nicholas Vinen Derby Street, Silverwater, NSW 2148. 2 Silicon Chip Australia’s electronics magazine siliconchip.com.au