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Sharp catches up on 'cool' handset craze

Posted: 05 Sep 2008 ?? ?Print Version ?Bookmark and Share

Keywords:Sharp handset teardown? mobile phone market? HSDPA? processor?

Japan always seems to be light years ahead of the West in all things technologically cool. The Japanese were always the first to get their hands on the latest game consoles, which always makes North American gamers green with envy.

These days mobile phones became the new must-haves. But having a cellphone isn't enough; it had to be a cool phone!even cooler than the Motorola StarTacs the rich kids owned. As my network of friends grew to include those of Japanese descent with access to the cellphones of their homeland, the StarTac was trumped, and I was truly amazed at how much sleeker and smaller their devices were.

The Japanese are still developing and manufacturing phones for their mobile market; new products are released every day from service providers like KDDI, Vodafone and Softbank. Our Japanese colleagues attend the launches and let us know which phones are generating buzz on the streets of Tokyo.

One is the Sharp 922SH, available through the Softbank network. A look inside this phone yields insights into whether the Japanese remain ahead of their global counterparts.

Sharp's 922SH features a 3.5-inch VGA screen and provides 480 x 584 resolution and a contrast ratio of 2,000:1. (Click to view teardown)

Peak inside 922SH
The 922SH is very similar in design to Nokia's Communicator line of mobile phones, which mimic laptops. Like the Nokia E90, the Sharp handset has a clamshell design that was probably chosen to highlight its ability to provide a comfortable environment for surfing the Internet (indeed, Sharp advertises the phone as an "Internet Machine"). To enhance the experience, the 922SH features a 3.5-inch VGA screen that uses Sharp's Aquos technology to provide 480 x 584 resolution and a contrast ratio of 2,000:1. Other features include Bluetooth connectivity and HSDPA, a 2.1Mpixel camera, and a business card scanner.

The handset uses two separate processors to handle baseband and application functions within the device. The Ericsson DB3150, typically found in Sony Ericsson mobile phones such as the K850i, serves as the baseband processor. Ericsson ICs are also used for the W-CDMA receiver and transmitter (the RF3000 and RF3100).

The applications processor marks a design win for the Toshiba Mobile Turbo TC35296. Referred to by Toshiba as the T5G, this media processor is designed specifically for handsets. Featuring an ARM926EJ-S CPU and three hardware accelerators!a video codec, 3D graphic accelerator and JPEG codec!the IC powers Internet and gaming applications and was manufactured at the 90nm process node.

Sharp ICs feature prominently in the design, but they are primarily used in relation to the Aquos VGA screen. The IXA186 is an LCD driver IC; the ICA189 is the display driver. The T10S10 1Seg (single-segment) DTV tuner provides the phone's touted multimedia experience (TV, Internet, etc.). The only Sharp IC that is distinguishable from those used in the Aquos screen is the C80414KA, an IR receiver.

Maxim Integrated devices are also found on the handset's motherboard. The MAX4368 is an ultrasmall audio power amplifier designed for use in mobile products. The ICL7641 serves as an operational amplifier.

ST package
Completing the design are two contributions from STMicroelectronics. The 2500C4 is a single-chip Bluetooth v2.0 device that provides increased connectivity to the phone. It is the other ST component, however, that proves to be of greatest interest!not because of what it can do, but because of how it is built.

A look inside the ST M39PNRA2A reveals five dice within a single package. The multichip package (MCP) comprises two types of flash memory in three dice, in combination with two identical SDRAM dice. It's a complex IC with intricate wire bonds leading from each of the five dice to the bonding elements of the package. The flash dice are two 512Mbit NOR devices from ST and one 2Gbit single-level-cell NAND component from Hynix. Completing the package are two Elpida 512Mbit DDR2 SDRAM dice in a 70nm process.

Die photos of the Elpida E5116AJBG-6E-E and the Elpida SDRAM featured in the ST MCP.

Comparisons with another 70nm Elpida device investigated by Semiconductor Insights (SI) show a series of differences. A quick look at both devices identifies the ST package SDRAM as a low-power version!understandable, considering the placement of the dice in a five-stack package. SI professional consultant John Boyd, however, noted that "the Elpida SDRAM in the ST package [with the die marking K5132CC] and the Elpida E5116AJBG-6E-E in SI's device library have an obvious difference in the direction of the routing within the die. The K5132CC die has the wires bonded to the outside of the die, compared with the E5116AJBG, where the wires are bonded to the center. This difference is intriguing in that it reveals that the Elpida device inside the ST package may be a custom IC."

A cross-section of the Elpida devices uncovers the same identical four layers of metal in both designs. That could indicate the development of a new mask set by Elpida for the specific ST package requirement, which in turn would suggest a partnership between ST and Elpida.

Why use such a complex package for memory? Simply put, in a space-constrained device like a cell phone, a multichip package is perfect for creating more room on a small circuit board.

The MCP however, does have its disadvantages. Boyd noted that MCP development requires significant thinning at the wafer level, especially when five dice are required. That puts serious constraints on the manufacturing process, since these extremely thin wafers (thin enough in some cases to see the circuit design pattern on the back side) must be stress relieved after thinning and handled with specialized equipment. That leads to potential yield problems, since breakage can reduce production yield.

In addition to the need for testing each die to ensure functionality, testing must take place after packaging, with five levels of challenging wire bonds. Each level increases the probability of failure, since it adds more steps and more time to the manufacturing process. It's fairly obvious, though, that these disadvantages do not outweigh the advantage of space conservation. Given customers' expectations for ever more compact devices, manufacturers make sacrifices to meet that demand.

North America's pride
After taking a look inside the Sharp 922SH and various other mobile products from Japanese vendors, it is fair to say that Japan's designers still take pride in avant garde technology. But one cannot discount the designers in North America and Europe, as companies such as Apple and Nokia have shown new levels of innovation in products such as the iPhone and the N95. These products and many others being released in the upcoming year suggest the "wow factor" will be kicked up a notch. The real winner in the competition to design the newest, "coolest" phone is the consumer.

Now, if Apple would only make a calculator watch that runs on water and plays MP3s, I'd finally be able to one-up my friend Hiro.

- Allan Yogasingam

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