Inside Motorola's Slim SLVR

Motorola’s first iTunes phone looked lean at less than an inch in width when it was introduced last fall, but the SLVR L7, at 0.45 of an inch, cut that Z dimension almost in half.

The SLVR (Figure 1) is noticeably longer and wider than the ROKR (Figure 2) (4.5 x 1.9 inches versus 4.3 x 1.8-inches). But where the SLVR is larger in size, it is stylishly slimmer, lighter, and less expensive than its predecessor.

The SLVR and the ROKR both have a 1.9-inch, 176 x 220 TFT display capable of up to 262K colors. Both provide a VGA camera with video capture/playback, optional expandable memory and, of course, iTunes. Either model can hold approximately 7 hours of music, or about 100 songs.

The SLVR phone continues the thinner-is-better trend that Motorola launched with its "clamshell" RAZR (Figure 3) phone in 2004.

"Sixty percent of the world buys bar phones, and we wanted to give those buyers something as iconic as the RAZR was for clamshell buyers," said Steve Lalla, Motorola’s vice president and general manager for mass-market products. "Our objective was to redefine what a bar phone was—something cool, and showy; an object of desire to own."

To achieve that objective the SLVR not only had to be super thin, but it also had to project an image of quality and durability. And it had to be economical to manufacture.

Motorola’s first iTunes phone was based on Freescale Semiconductor's DSP56631 dual-core (130MHz Freescale DSP56600 DSP and 52MHz ARM7TDMI-S MCU) baseband processor and MC13777 quad-band GPRS front-end IC. Lalla said his team decided to stick with the DSP56631 for the SLVR, but went with a customized version that has 4Mb (128Kx32) of RAM and 1Mb (32Kx32) of ROM for the ARM7. The SLVR also includes Freescale’s MC13890 power management and user interface device. The front end consists of two chips from RF Micro Devices’ Polaris 2 TotalRadio Module—the RF6025 transceiver and RF3178 transmitter.

Other major components in the SLVR, according to David Carey, president of Portelligent, Inc., who has examined the inside of the SLVR, include an Imageon 2240 media processor (ATI Technologies), an Intel Stacked-CSP memory module containing a 32MB Intel NOR flash chip, and an 8MB Micron Cellular (pseudo-static) RAM. A Broadcom BCM2035 Bluetooth chip, which is mounted on a daughter card, includes an Epcos SAW front-end filter and a score of other passive components.

"Freescale’s architecture includes a digital baseband DSP and a separate controller core that also incorporates the analog baseband and the audio interface," said Carey. "It’s a mixed signal chip; a different partitioning from some other cell phone architectures."

The DSP56631 includes receiver A/D converters, an RX/TX synthesizer, power amplifier control, reference oscillator, a serial audio port, and a voice codec for use with complete GPRS/EDGE applications.

The MC13890 integrates buck and boost switchers, LDO regulators, handset and headset microphone amplifiers, receive path audio amplifiers, a Li-Ion battery charger, a 10-bit A/D for battery monitoring, 16-bit stereo D/A with analog and digital audio interface, a 13-bit voice codec, an SSI audio bus, SPI bus, power control logic, a 32kHz crystal oscillator with an internal backup oscillator, a USB transceiver, and backlight drivers.

RF Micro Devices’ RF6025 quad-band transceiver, a customized version of its RF6026, implements VLIF and DCR architectures and eliminates the need for IF filters. Integrating VCOs and associated loop and SAW filters for a lower component count, the device uses digital channel filtering in its receive section for improved performance even under temperature, voltage, and processing variations. It can output a fully filtered DC signal in analog I/Q or digital formats. The RF6026 transmit section includes fractional-N-based digital modulators for enhanced spectral performance with lower power consumption. Integrated power amplifier control circuitry eliminates the need for external power detectors or feedback circuits. The RF3178 transmitter integrates the power amplifier, Rx/Tx switch, power controller, and harmonic filters.

Components in the SLVR L7 were selected in part for their ability to conserve space. The media processor integrates a 2D graphics engine, camera subsystem processing engine, and video acceleration. Both devices in the memory module share the same bus. Power consumption is a major concern. Consumption in the cellular RAM can be as much as much as half that of equivalent LP DRAM in active mode, and 95% lower than SDRAM in standby. The cellular Ram also offers a burst interface for better throughput.

Motorola’s engineers’ ability to pack components closely together without affecting RF performance was key to the SLVR’s design, Lalla said. A J-shaped antenna at the bottom of the phone is connected to the main pc-board by a thin coax cable.

"There aren’t as many ‘mechanical heroics’ in the SLVR as there are in the RAZR," said Portelligent’s Carey, "but it’s a thoughtful layout. The circuit boards and the battery nest alongside each other nicely. The fact that component vendors hid complexity allows Motorola to reduce board size and stack two boards together to form a relatively compact system."

Carey estimated the SLVR to be less expensive to build than the RAZR, with anodized aluminum used in place of cast magnesium. Its keypad is manufactured with a non-conductive, vacuum metallization process that gives it a metallic look and feel without affecting RF performance.

"The phone’s internal PAA-resin plastic frame and associated stamped metal components provide strength without the cost of cast enclosures," Carey said. "Additional contributions from the anodized aluminum exoskeleton and the stiffness of the internal battery give the SLVR structural rigidity and a solid feel."