Digital tuners don't get canned

-- EDN, 1/6/2000

Broadcom and Conexant have released silicon tuners to replace traditional bulky tuner cans. Besides replacing as many as 200 discrete parts, the tuners also eliminate the need for 9 or 28V power supplies that tuners typically require. Broadcom's BCM3400 family is a complete digital-analog RF television tuner in CMOS targeting consumer devices, such as televisions, video recorders, cable modems, set-top boxes, and PC/TV devices. The first member of the family, the BCM3415, integrates the signal-processing circuits required to select a requested channel in the 50- to 860-MHz cable band, amplify it, and downconvert it to a standard 44-MHz IF signal using a triple-conversion architecture. Control of chip parameters takes place over a two-wire MBus-compatible serial interface. The family also integrates all external-oscillator "tank" components associated with RF VCOs, which removes noise from external pins and thereby simplifies RF layout and the need for extensive shielding. The BCM3415 comes in a 48-pin TQFP and is available in sample quantities; volume prices are $10 to $12.

Conexant's offering is the single-chip InfoSurge CN2811 digital-cable tuner targeting cable modems and set-top boxes. The company will sell the device with the CN9414 single-chip programmable cable modem, which can support online software upgrades through a programmable media-access-control layer. The CN2811 consumes less than 1.5W of power and provides a complete tuner system from the coaxial cable input to the A/D-converter input of the CN9414. The CN2811 accepts RF signals of 44 to 870 MHz and converts them to IF signals at 36 or 44 MHz. Missing are a preamplifier and an automatic-gain-control circuit to condition the input signal, filters, and external tank circuits. The tuner is available for sampling, and volume production is scheduled for the second quarter. The device comes in a 48-pin ETQFP, and price, including the CN9414, is $40 (10,000).

Broadcom, 1-949-450-8700, www.broadcom.com.

Conexant, 1-949-483-4600, www.conexant.com.

-by NicholasCravotta