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News and New Products
Integrated ADSL chip set drops analog traces
By Nicholas Cravotta -- EDN, 10/2/2003
Texas Instruments’ new 16-port AC7 multiservice ADSL CO (central-office) chip set is the company’s seventh-generation CO offering (Picture). The two-tier chip set, including a digital processor that integrates an analog front end, provides further integration of DSL functions and passives. The AC7 supports ADSL, ADSL2, ADSL2+, Annex L, READSL (reach-extended-ADSL), and legacy-ADSL protocols on any port through software provisioning.
Key to the architecture is what the company calls analog-signal-trace elimination. Tradi-tional architectures require a differential analog signal between drivers and the external codec. The AC7 digitally serializes signals from the driver directly to the DSL chip set, eliminating the complexities of running analog signals. Additionally, the chip set lets you aggregate data and control signals, traditionally parallel signals, to a single high-speed-serial interface, reducing trace count, simplifying board layout, lowering ASIC/FPGA pin count, and reducing pc-board costs.
The “any-service, any-port” architecture of the AC7 reduces hardware-development ex-penses by allowing one chip set and one board design to serve multiple applications through-out the network. The architecture also lowers software investment through backward compati-bility with previous Texas Instruments CO chip sets. Such an architecture enables vendors to immediately provide various flavors of ADSL service rather than waiting until enough custom-ers sign on for a service to make it feasible to install a line card with that application.
The AC7 chip set integrates memory and analog self-test; it is backward-compatible with legacy CPE (customer-premises equipment) and has a variety of ports, including Utopia 2, POS (Packet over SONET), LVDS high-speed serial, pulse-code modulation, and a manage-ment port. The Texas Instruments interoperability lab can test devices against 225 CPEs and more than 30 DSLAMs (digital-subscriber-line-access multiplexers).
A 16-port line card, for example, requires one 16-port digital transceiver, eight two-port analog front ends, 23 discrete components per port for a total of 368, and one transformer. Power consumption in this configuration is less than 750 mW.
The device is available for sampling, and production is slated for early 2004. The AC7 chip set sells for less than $10 per port (production volumes), translating to $160 for nine chips supporting 16 ports
Texas Instruments, www.ti.com/dsl.
