Handspring Treo 600 Smartphone: analog is key

The Treo 600 is Handspring's popular PDA/phone combo terminal, based on the Palm OS and"in the case of the unit analyzed here"incorporating a GSM cellular radio. As is often the case, analog components are key to making this digital wunderkind fly.

Electronics reside primarily on the single Main Board where a Texas Instruments OMAP310 applications processor forms the computational heart of the Treo 600. 32Mbytes of Infineon Mobile RAM for working memory and 8MBytes of AMD NOR flash take care of code store and user non-volatile memory. The integrated camera from Micron Technologies includes a 10-bit A/D converter to enable a direct interface with the OMAP310's embedded image co-processor.

Using a TFT LCD screen with a touch screen overlay, the Treo 600 employs a Wolfson #WM9705 touch screen controller while a TI boost converter for the LCD panel bias and Semtech white LED driver pick up remaining LCD analog tasks. The miniature QWERTY keypad is backlit by an electroluminescent film, whose high-voltage AC power is supplied by a Durel #D355B.

For audio output the Wolfson #WM9705 is used again, incorporating an audio CODEC along with the touch screen controller. Digital audio information from the OMAP310 is converted to an analog signal in the Wolfson part and a pair of Texas Instruments class-AB audio amplifiers are tapped for directly driving the Treo's earpiece and speaker. A stereo amplifier internal to #WM9705 serves during headphone use.

Power management remains a piecewise solution in the Treo. A Semtech #SC801 is the front line for Li-Ion battery charge management while internal to the battery pack, a Dallas-Maxim #DS2760 provides current/ voltage monitoring and under/over voltage protection. Four separate DC-DC converters from TI and Torex address supply needs on the main board and for the cell phone module, where several Ricoh LDO regulators further manage voltage levels. Silicon Lab's Aero chipset"a masterpiece of CMOS analog RF engineering"is paired with a Broadcom baseband to implement the GSM phone in a matchbook-sized cell phone assembly which plugs into the main board.

While the Handspring has received knocks for a middling display and the micro-sized keyboard challenges the average set of fingers, the design highlights that cool things emerge from the ever-integrating digital chipsets available. Nevertheless, it still takes a sizeable basket of analog content to bring it all together.

David Carey is President of Portelligent. The Austin, Texas company produces teardown reports and related industry research on Wireless, Mobile, and Personal Electronics. (www.teardown.com)