Packaging aids 3G phone evolution

Third-generation handsets have been burdened by high complexity and cost. But with end-user volumes building and a certain measure of maturity setting in, phone makers are fielding devices that look more and more like their 2G predecessors-at least to a point.

With Universal Mobile Telecommunications System communications now making tentative steps into U.S. markets, it seems like a good time to look at another chapter in the evolving 3G handset story. In an earlier report, we talked briefly about a previous entry in Motorola Inc.'s UMTS handset evolution (search www.planetanalog.com for article ID: 2680-6489). This report looks at one of the manufacturer's follow-on phones, supported heavily by semiconductor content from Freescale Semiconductor Inc. but with advancements visible and hidden.

UMTS phones, by definition, blend legacy GSM and advanced wideband-CDMA standards into a common platform, representing a taller 3G engineering hurdle than single-protocol designs. Dual baseband protocols and their associated signal processing-along with completely different radio designs-must all be crammed into handsets that retain 2G-like form factors and battery life. Factor video imaging, location-based services and other media functions into the "3G expectation," and keeping everything under control becomes an integration battle.

But as with any relatively new technology market, the compaction of 3G feature sets is occurring on slippery ground. Consumer expectations are still shifting, and feature sets remain in a relative state of flux as users and carriers experiment with the balance between desirable services and profitable businesses. All the while, of course, handset manufacturers are under constant pressure to keep a lid on system complexity and costs.

Enter the system-in-package emphasis of Motorola's E1000 handset, where multichip and mixed-technology assembly try to deliver inner complexity, outward simplicity and an element of flexibility.

Starting with the feature set, the E1000 bundles UMTS communications with stepped-up graphics, MP3 playback, MIDI support and plenty of other bells and whistles. Built-in assisted-GPS positioning capability, push-to-talk support, Bluetooth and a dual-camera design (1.2-megapixel capture with image editing) pile on to increase system hardware and software sophistication.

Core communications support for the E1000 derives from a Freescale platform that includes the baseband, baseband interface and transceiver.

The PCM29415 package contains four IC dice, including the baseband processor, 2 x 32-Mbyte Intel NOR flash and 16-Mbyte Samsung Mobile DRAM. It's one part on the outside but many within, leaving room for external footprints to remain constant while internal capabilities can change through package-level assembly, not new IC tapeouts. Discrete-component implementations are an option, of course, but at the expense of increased board-level real estate-and complexity-for Motorola and its manufacturers.

A second chip, the MMM7200, interfaces the baseband memory assembly to radio circuitry composed of, and spread between, two additional packages. The PMM6017 is a three-chip module containing a GSM transceiver, a W-CDMA receiver and an RF synthesizer, used to generate appropriate signals for up- and downconversion in the radio as a whole. Almost 50 passive components associated with the three-chip complex are also supported in the PMM6017 package.

A second page, the MMM6016, handles W-CDMA transmit. It houses a single IC along with a surface-acoustic-wave filter and its own set of RF passives.

The message in this partitioning is that while the time-division, mature GSM protocol can be rendered in a single slice of silicon, the more difficult, newer W-CDMA full-duplex radio still benefits, for now, from separating the transmit and receive path semiconductors. All of the partitioning issues, however, are largely hidden at the board-level view, where the objective is to bury complexity and keep the system design clean.

Rounding out the communications aspect of the E1000 is a Texas Instruments Inc. custom part, the TWL93010B, that is responsible for centralized system power management, though local regulation and voltage-conversion components can be found throughout the design. Two RF power amplifiers tackle final-stage RF transmission, with Skyworks Solutions Inc. supplying its system-in-package mixed-technology power amplifier module for GSM and RF Micro Devices Inc. chosen for the single-band W-CDMA protocol.

Wireless videoconferencing
Outside of Freescale's platform, additional horsepower to drive the QVGA TFT LCD comes from Nvidia Corp. via the GoForce 4000 media processor. This same device also manages the camera interface from a dual-camera, 1.2-Mpixel/Common Intermediate Format module, with the high-resolution sensor used for stills and the CIF device used for wireless videoconferencing. The two imagers are based on CMOS process technology and are supplied by Omnivision Inc.

Both the Freescale GPS solution (MG4100) and Broadcom-based Bluetooth chips rely further on complex package-level assembly to shrink-wrap functionality while blending mixed component types.

While other UMTS chip makers have leaned toward monolithic solutions, Freescale has gone to market with a mix-and-match of diverse building-block ICs configured partially at the package level. Is multichip packaging a stopgap or a panacea to deal with modest early volumes and uncertain chip specs? Perhaps a little of both.

By David Carey, president of Portelligent (Austin, Texas), which produces teardown reports and related industry research on wireless, mobile and personal electronics (www.teardown.com)