Electronic Design

Upstream Amplifier Targets Set-Top Boxes And Cable Applications

The MicroStreamer MT1530 IC amplifier from Microtune moves data from the user upstream and then back to the head end in a broadband cable system. Designed for set-top boxes, cable modems, cable telephones, and other cable applications, this device meets ITU/CableLabs Data Over Cable Service Interface Specifications (DOCSIS) and European DOCSIS. It is pin-for-pin and software compatible with other industry-standard devices.

In duplex broadband systems, a set-top box or cable modem includes an RF tuner for selecting downstream 6-MHz channels in the 54- to 852-MHz range. Upstream data is transmitted on channels within the 5- to 42-MHz range. The upstream signals must be amplified prior to being applied to the cable. Upstream channels are allocated by type of service and line conditions. Channel bandwidth may vary between 0.5 and 2 MHz. Data rates of up to 200 kbits/s are achieved with QPSK or QAM16 modulation.

The MT1530 sets new standards for an amplifier in this application. It has a bandwidth of 5 to 65 MHz and can put a maximum of 64 dBm into a 4:1 output transformer. Also, it has a total gain of 63 dB variable in 1-dB increments with a 6-bit serial gain control word. It offers lower power consumption and lower harmonic distortion than any of its competitors as well.

This amplifier consumes a maximum of 500 mW at maximum gain and about 150 mW at minimum gain with a 5-V supply. In the shutdown mode, the power is about 650 µW. Harmonic distortion is less than −70 dBc for the second harmonic and −55 dBc for the third harmonic.

Made from 0.8-µm biCMOS, the MT1530 comes in a 20-pin SSOP package. It costs $3.50 each in 10,000-unit quantities. Production quantities are available now.

Additionally, Microtune's MT2000 and MT2500 single-chip TV tuners are available along with the MicroStreamer MT1530 amplifier in completely tested OEM modules for set-top box and cable-modem manufacturers.

Microtune Inc., 2540 East Plano Pkwy., Ste. 188, Plano, TX 75074; (972) 673-1600; fax (972) 673-1602; Internet: www.microtune.com.

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