Direct-Conversion Tuner IC for Digital DBS Applications

The MAX2104 low-cost direct-conversion tuner IC is designed for use in digital direct-broadcast satellite (DBS) television set-top box units. Its direct-conversion architecture reduces system cost compared to devices with IF-based architectures. The MAX2104 directly converts L-band signals to baseband signals using a broadband I/Q downconverter. The operating frequency range extends from 925MHz to 2175MHz.

The IC includes an LNA gain control, I and Q downconverting mixers, lowpass filters with gain control and frequency control, a local oscillator (LO) buffer with a 90° quadrature network, and a charge-pump based PLL for frequency control. The MAX2104 also has an on-chip LO, requiring only an external varactor-tuned LC tank for operation. The output of the LO drives the internal quadrature generator and dual modulus prescaler. An on-chip crystal amplifier drives a reference divider as well as a buffer amplifier to drive off-chip circuitry. The MAX2104 is offered in a 48-pin TQFP-EP package.

Applications

* Broadband Systems * DirecTV, PrimeStar, EchoStar DBS Tuners * DVB-Compliant DBS Tuners * LMDS

* Low-Cost Architecture

* Operates from Single 5V Supply

* 925MHz to 2175MHz Input Frequency Range

* On-Chip Quadrature Generator, Dual-Modulus Prescaler (/32, /33)

* On-Chip Crystal Amplifier

* PLL Mixer with Gain-Controlled Charge Pump

* Input Levels: -25dBm to -65dBm per Carrier

* Over 40dB Gain Control Range

* Noise Figure = 11.5dB; IIP3 = 7dBm (at 1550MHz)

* Automatic Baseband Offset Correction

* Loopthrough Replaces External Splitter

* Crystal Output Buffer