PDA nears wireless trifecta

The PDA market is in the midst of an identity crisis. Long heralded as the electronic potion to organize one's life and bring the PC to the pocket, the personal digital assistant must now up the ante to stay relevant.

PDA shipments in 2004 are variously put at about 10 million units-a fraction of the 600 million-plus wireless handsets that shipped last year. The numbers tell us people want to chat more than they want to get electronically organized. Some estimates place pure-PDA shipments on the decline, reinforcing the need for "something new" if the PDA industry wants to relive its halcyon days in market expansion. Now, wireless fuels renewed growth hopes.

Sporting Microsoft's Windows Mobile 2003 and MS Pocket Office Suite, Hewlett-Packard Co.'s iPAQ 4355 features a host

of connectivity modes, including built-in 802.11b Wi-Fi, Bluetooth and IrDA, but no cellular data connection. The 4355 is an inch longer than the earlier HP 4150 due to a long-awaited addition of a thumb keyboard to the touchscreen.

The keyboard is for an input-intensive user, but you'd better have deft thumbs for its diminutive keys. An equally diminutive on-screen virtual keyboard is an option for those who prefer tap over tactile input and-unlike the thumb board-the virtual keyboard can be hidden when idle.

An Intel PXA255 400-MHz Xscale processor powers the 4355. It's supported by 64 Mbytes of Samsung SDRAM (2 x K4S561633C-RL75) and 32 Mbytes of NAND DiskOnChip flash (MD3831-32) from M-Systems. The M-Systems device acts as a solid-state drive, surrounding normally block-read NAND technology with circuits to do error correction and enable a randomly addressable NOR/SRAM interface while leveraging the cost-per-bit economies of multilevel-cell NAND.

Acting as connectivity peripherals are the Wi-Fi and Bluetooth functions, the former implemented by combining Texas Instruments baseband silicon (TNETW1100) and a Maxim direct-conversion RF transceiver and power amp (MAX2820 and MAX2247 respectively). Reflecting the industry's rapid progress in mixed-signal, the TI BRF6101 Bluetooth solution combines digital baseband and RF transceiver functions in a monolithic solution.

Other notable components are an audio codec from Philips (UDA 1380HN), a touchscreen interface from Burr-Brown/TI (ADS7846), a microcontroller from EMC (EM78P451) and power chips from Semtech, Torex, National, TI and AME. For all the integration in key logic, memory and wireless components, the design reflects the unique power-management solutions that typify PDA implementations. There is simply not enough opportunity for a high-volume standardized product in rapidly evolving PDA designs to justify the ASIC power-management solution so often seen in the cell phone arena.

The electronic components for the 4355 reside on a Matsushita eight-layer ALIVH main board-structurally, an organic equivalent to multilayer ceramic-and a simpler six-layer buildup circuit card for the keyboard. The 64k-color, 240 x 320-pixel transflective display module was supplied by Sony and is illuminated by six white LEDs on a flex light strip.

The unique audio design transmits sound around the keys on the front enclosure, with the speaker ports in the keypad protected by a felt covering. Surface-mount cans cover the 802.11b transceiver, and memory chips of the main board and enclosures are sprayed with a conductive paint for EMI management.

Estimated cost of goods sold (COGS) was under $200 including a docking cradle and other accessories, bringing COGS to less than half of the $499 purchase price.

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