Under the Hood of Motorola's A920: UMTS drives multi-radio systems

3G cellular service is on the rise, with correspondingly more complex handset designs. Motorola's A920 UMTS terminal is from a crop of multiband, multi-protocol designs which offer up wireless video, web browsing and of course"voice communications. UMTS is a mix of legacy GSM and newer W-CDMA services which together kick up analog content in the radio area and demand more acute power management in light of UMTS's added battery burden.

Some of the A920 circuitry is based around early forms of Motorola's i.300 platform of 3G cellular components. A Motorola #PC55061 appears to interface both GSM and W-CDMA paths to the company's #SC29411VF digital baseband"itself boosted by with a TI OMAP1510 applications processor.

For the W-CDMA radio, a pair of Maxim components (#MAX 2363,/#MAX2309) along with a Motorola LNA/Mixer (#770) and RFMD power amplifier (PA) module are used. Similarly, a Motorola #PC79903VH GSM Transceiver and LNA/Mixer form the GSM radio path with a Skyworks PA for final stage transmit. A TDK RF Front-End module manages the rather complex distribution of transmit and receive signals between the A920's antenna and its two radios with three bands of service coverage.

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But UMTS is about more than multiple cellular radios, and additional wireless abounds. For location-awareness, a SiRF StarII GPS chipset (#GSP2e and #GRF2i) enables the A920 to acquire localized maps and even receive directions to the nearest restaurants of choice. Lest you still feel unconnected, a Broadcom #BCM2033 single-chip Bluetooth radio/baseband provides local communication with handsfree headsets or other gadgetry for data-sharing.

The Broadcom part"along with Bluetooth chips from others"are pushing the envelope in mixed-signal IC design to dish up highly-simplified local area radios. Expect GPS offerings to progress along a similar path with some manufacturers already claiming single-chip GPS solutions. Of course not all the analog action lives in the RF domain. TI's ASIC (#TWL93010B ) serves systemlevel needs to orchestrate power draw while a slew of smaller-scale devices tackle local sub-system regulation. California Micro Devices' #304 ESD Filters mirror a general use of silicon-based passives in handsets to guard against human keyboard and connector zaps that could cripple internal electronics.

Par for the course in all 3G handsets, the A920 shows that increased digital technology in terminals brings with it increased analog content.

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)