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Inside iPod touch: Did Apple tip its hand?

Posted: 17 Oct 2008     Print Version  Bookmark and Share

Keywords:iPod touch  NAND Flash  Bluetooth  FM receiver 

Apple's new line-up of iPods included changes to the shuffle, nano and touch. Semiconductor Insights was eager to see what components were different between the first- and second- generation touches, as well as compare it with the iPhone 3G, which was released only months ago.

The iPod touch offers interesting technology improvements that put it on par with the iPhone when used as a multimedia player. The screen size and resolution remain the same, but speakers were added, as opposed to the piezoelectric sound from the previous generation, which was only used to make the basic sounds, like clicking when the device was unlocked. The volume can now be controlled with an external button instead of changing the levels on the touch screen. This has been a feature of the iPhone, and is a welcome addition to the touch. Finally, the battery life is estimated to have been extended by an hour during video playback and eight hours during music playback.

We identified two significant component changes in the iPod touch. First is the manufacturer of the NAND Flash memory. The 8GB iPod touch contains Micron NAND Flash. The previous touch had memory supplied by Samsung and the iPhone 3G uses Toshiba; this shows that Apple is no longer playing favourites with any particular memory manufacturer. In the past, Apple had an agreement with Samsung to provide the memory devices, but that has apparently expired‚Samsung memory has not been identified in the iPhone 3G or second-generation iPod touch systems we analysed. This could be due to the fact that other manufacturers are offering a lower price, that Apple demand is too high for any single vendor to handle, or that Apple has multiple second-source vendors to ensure an adequate supply of NAND flash.

Die photo of Broadcom BCM4325 Bluetooth and FM receiver

The second change, and more significant, was the inclusion of the Broadcom BCM4325. This is a low-power 802.11 a/b/g with Bluetooth 2.1 + enhanced data rate (EDR) and an FM receiver. This device provides the wireless connectivity to access Web sites, iTunes and apps store, and communicate with accessories like the Nike+ iPod Sensor (which does not need the Sports Kit when used with the second-generation iPod touch). The Wi-Fi feature has two options, either a single-band 2.4GHz 802.11 b/g or a dual-band 2.4GHz and 5GHz 802.11 a/b/g. The part number referenced on the device taken from the second-generation Apple iPod Touch is BCM4325GKWBG, which is the single-band solution.

When the iPhone 3G was released there was speculation about Apple choosing an integrated chip for the Wi-Fi and Bluetooth capabilities. It was surprising, then, that Apple implemented a two-chip solution—the Wi-Fi powered by Marvell's 88W8686 and the Bluetooth from Cambridge Silicon Radio's BlueCore6 device.

The Broadcom device

The Broadcom device was manufactured using a 65nm process technology. This enables a die size of 6.5mm x 5.8mm = 37.7mm¾ in a Wafer Level Chip Scale Package (WLCSP). Compared with the two components from Marvell, measuring 4.7mm x 4.1mm = 19.3mm¾, and CSR, measuring 3.5mm x 3.2mm = 11.2mm¾, this is an increase of about 7mm¾, but it does not take into consideration the fact that more board real-estate is taken up with traces to connect the two devices.

Usage of advanced design techniques allows the BCM4325 to deliver the functionality in a power-efficient manner to extend the battery life in consumer products. An integrated power-management unit simplifies the power topology of the system. The flexible power amplifier scheme (allowing both internal and external power amplifiers) makes this solution suitable for a wide range of mobile applications.

The BCM4325 is designed to address the needs of mobile devices that require minimal power consumption and reliable operation. Broadcom's integrated solution offers advanced co-existence algorithms to maximise the performance of multiple wireless connectivity options within a single device. Even as FM radio continues to gain momentum in mobile systems, Broadcom' s implementation offers the advanced features required for entertainment and live news broadcast reception in today's handsets.

Die marking of Broadcom's BCM4325 Bluetooth & wireless receiver

Interestingly, Apple has not indicated that the iPod touch even had Bluetooth functionality. And though the Broadcom device has the capability, there are not, as yet, any applications to take advantage of this feature.

So has Apple tipped its hand about new features for the iPod touch? There are many applications that could easily be added to the player with only a slight change to the firmware code. Considering the ability to connect wirelessly to the Internet, Apple could introduce VoIP capabilities with a Bluetooth headset, or even just add Bluetooth wireless stereo headphones for listening to music.

Of course, it could just be a cost-cutting measure—Apple may have been able to get a volume-purchase price that made it a cost-effective solution for the iPhone and the iPod touch, even if all the functionality might not be enabled in the latter. Further analysis of an iPhone 3G is needed to determine if Broadcom is being designed into that system as well. tip

- Gregory A. Quirk
EE Times

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