Electronic Design

Single-Chip Modulators Target VHF/UHF TV Applications

Designers seeking low-voltage and VHF/UHF booster/splitter functions now have a more elegant solution. Two modulator ICs from Motorola, the MC44BC373DTB and MC44BC374DTB, integrate the antenna, booster/splitter, and traditional VHF/UHF multichannel modulator functions. They also combine all sound subcarrier and VHF/UHF voltage-controlled-oscillator circuits on a single chip.

These advanced-biCMOS 5-V chips target low-power applications like VCRs, DVD players, video games, and analog and digital set-top boxes for satellite, terrestrial, or cable television. They also eliminate the need for external varactor diodes or coils. Additionally, they solve the sensitivity problems related to bonding-wire and pc-board stray capacitances and inductances. The MC44BC374DTB suits PAL/NTSC applications, while the multistandard MC44BC373DTB fits PAL/NTSC/SECAM uses. Both are offered in the space-saving TSSOP24 package.

Extremely versatile, their modulator section is fully controlled by a high-speed I2C- compatible bus, offering several test modes for easier production. The multistandard version's modulator corresponds to all worldwide standards by operating on channels 21 to 69 in the PAL, NTSC, and SECAM standards, while the sound subcarrier is selectable to 4.5, 5.5, 6.0, and 6.5 MHz. The modulator operates in the VHF range by selectable internal divider ratios.

Extended functions, enhancements to the present MC44353/4/5 family, include a 2-mA logic output port that can be used to drive an attenuator, internal VCOs, improved attenuation with output inhibit, a second sound subcarrier input (stereo or NICAM), and a power-on default mode for channel 36 (B/G) without the need for programming the I2C bus. Also, the antenna booster and splitter section operates from 40 to 860 MHz. It provides exceptional gain flatness and isolation performance. The inputs from the antenna and the modulator section are added internally to feed the TV output.

A third IC, the MC44BC380D, is available as well. This low-end modulator can be used in picture-in-picture TV sets and other similar applications. The MC44BC380EVK development kit is available too, but it isn't required.

In 10,000-unit lots, the suggested resale price for the MC44BC373DTB, MC44BC374DTB, and MC44BC380D is $2.00, $1.68, and $0.65 each, respectively. All three are available in an SOIC8 package. The MC44BC380EVK development kit has a suggested resale price of $300. A complete development kit with a populated application board, 10 samples, software, connectors, a PC interface, and a user manual (the MC44BC373EVK) is available with a suggested resale price of $600.

These three modulators are now available in sampling quantities. The MC44BC380D is already in production, and the MC44BC373DTB and MC44BC374DTB are expected to be available in volume-production quantities during the fourth quarter.

Motorola Inc., 1300 N. Alma School Rd., MD:CH290, Chandler, AZ 85224; (480) 815-5032; www.motorola.com.

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