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Nüvi 205 expands horizon for GPS navigation system

Posted: 01 Dec 2008 ?? ?Print Version ?Bookmark and Share

Keywords:Nuvi 205 teardown? GPS? navigation device? PND?

GPS boxes have been on a steep price decline lately and a product release from Garmin Ltd seeks to embrace the next wave of users with a sub-$200 price point and within reach retail placement.

The $199 Garmin N�vi 205 is one of the first "blister-pack" personal navigation devices (PNDs) I've seen. Clear, vacuum-formed packaging around the product itself and unlocked rows of these on an open-floor retail shelf caught my eye at the local big-box electronics dealer. No longer at prices that force PNDs into locked glass cabinets, the N�vi 205 and its presentation all speak to the growing commodity status of standalone GPS systems.

Garmin is neither the first nor the only vendor to field a $200 or less PND, but the N�vi 205 comes with a rich feature set given the price. A 3.5-inch diagonal 320 x 240 touchscreen has full color 2D and 3D mapping data from Navteq Corp., all preloaded on the device. Turn-by-turn audio directions are provided, along with optional FM-band traffic information and news via MSN Direct services. Geotagged photos from Google's Panaramio can be loaded into a user-supplied MicroSD card to give a more visual experience than maps alone can convey.

The N�vi 205, with its rich feature set, low price and easy-reach retail placement, is driving the commoditization of standalone GPS systems. (Click image to view teardown.)

Simplicity out of the box
Even key accessories like a car charging adapter and windshield-mount hardware are included, so there aren't many tack-on costs to achieve a fairly complete navigation experience right out of the box.

Consistent with an entry-level user target, the external interface is simple. The white plastic case has only on/off/lock slide switch along the top, a USB connector in the back and a MicroSD expansion memory card slot along the side. A reset button hides under a molded tab in case system operation grinds to a halt due to lockup. It seems some things never change.

Opening the two-piece case, after removing two screws hidden under the product label, one will find a single PCB supporting all system electronics. A ZIF connector on the board is used to wire in the LCD touchscreen module held by friction fit into the upper case half. Three more screws hold the board into the lower enclosure and once removed, the 3.7V/1,250mAh Li-ion battery and 8? speaker under the board are exposed. Both speaker and battery use discrete wire plug-in cables back to the PCB. Garmin claims both battery use and charge times are 4hrs.

The circuit board carries all receiver and processor functions with an eight-layer drilled glass-epoxy PCB technology. By careful placement of parts to optimize signal flow and equally careful component pad pitches to enable "escape routing" through conventional drilled vias, the added cost of high-density buildup board technologies can be sidestepped. When low price points are combined, even a small BOM cost reduction is a key. Every dollar matters.

Garmin makes use of highly integrated chips to keep component cost down and, architecturally, the design is split into just three bucketsGPS processing, memory, and analog.

Chip details
In the main role of GPS processing, an STA5620 single-chip RF front-end from STMicroelectronics demodulates and converts RF signals from the internal 25mm2 ceramic block patch antenna. Because there are fewer form-factor constraints that would be found with GPS in a cellphone, for example, the largish antenna can still be tucked into the product, offering better gain than a small stamped-metal aerial. A Maxim Integrated Products Inc. LNA fronts the receiver chip to further enhance SNRs for fast time-to-fix.

Signals from the RF receiver pass to the largest device, a Garmin-ST-marked processor that handles the GPS correlator functions along with system control and peripheral support. The Garmin-branded package has many of the physical attributes and similar functional attributes of STMicroelectronics's ARM-powered STA2062 "Cartesio" device, an obvious possible companion to the ST RF front-end. Speech synthesis, LCD control, MCU functions, USB and memory interfaces are all cooked right in.

System memory for the processor comes from 32Mbyte of DDR SDRAM from Hynix Semiconductor Inc. for working memory and 2Gbyte of iNAND flash from Sandisk Corp. The latter holds all mapping data and system codes (for download to DDR SDRAM) with the inclusion of a NAND controller to manage the host processor interface. Wear-leveling and error correction along with SD or SPI bus interface formatting are all handled in the controller chip, copackaged with what is almost certainly multilevel-cell (MLC) NAND silicon.

Other parts serve analog functions of the system. A Linear Technology Corp. LTC35571 takes care of USB battery charging and DC/DC conversion, and an LT3591 manages the white LED backlighting of the Sharp Corp.-manufactured LCD touchscreen. A Texas Instruments Inc. TSC2046 serves as the touchscreen controller and also supplies the two chips comprising audio functions with a stereo DAC (PCM1774) and audio power amplifier (TPA2010).

- David Carey
President, Portelligent





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