TDA8260TW

General description

The direct conversion QPSK demodulator is the front-end receiver dedicated to digital TV broadcasting, satisfying both DVB and DBS TV standards. The wide range oscillator (from 950 to 2175 MHz) covers the American, European and Asian satellite bands, as well as the SMA-TV US standard.

The Zero-IF concept discards traditional IF filtering and intermediate conversion techniques. It also simplifies the signal path.

Optimum signal level is guaranteed by gain-controlled amplifiers in the RF path. The 0 to 50 dB variable gain is controlled by the signal returned from the Satellite Demodulator and Decoder (SDD) and applied to pin AGCIN.

The PLL synthesizer is built on a dual-loop concept. The first loop controls a fully integrated L-band oscillator, using as a reference the LC VCO which runs at a quarter of the synthesized frequency.

The second loop controls the tuning voltage of the VCO and improves the phase noise of the carrier within the loop bandwidth. The step size is equal to the comparison frequency. The input of the main divider of the PLL synthesizer is connected internally to the VCO output.

The comparison frequency of the second loop is obtained from an oscillator driven by an external 4 MHz crystal. The 4 MHz output available at pin XTOUT may be used to drive the crystal inputs of the SDD, thereby saving an additional crystal in the application.

Both the divided and the comparison frequencies of the second loop are compared in a fast phase detector which drives the charge pump. The TDA8260TW includes a loop amplifier with an internal high-voltage transistor to drive an external 33 V tuning voltage.

Control data is entered via the I²C-bus. The I²C-bus voltage can be 5.0, 3.3 or 2.5 V, thus allowing compatibility with most existing microcontrollers.

A 5-byte frame is required to address the device and to program the main divider ratio, the reference divider ratio, the charge pump current and the operating mode.

A flag is set when the loop is 'in-lock', this can be read during READ operations, as well as the Power-on reset flag.

The device has four selectable I²C-bus addresses. The selection is done by applying a specific voltage to pin AS. This feature gives the possibility to use up to four TDA8260TW ICs in the same system.

Features

• Direct conversion Quadrature Phase Shift Keying (QPSK) and 8-Phase Shift Keying (8PSK) demodulation (Zero-IF)
• Frequency range: 950 to 2175 MHz
• High level asymmetrical RF input
• 0 to 50 dB variable gain with AGC control
• Loop-controlled 0 to 90Deg phase shifter
• High AGC linearity (<1 dB per bit with an 8-bit DAC), AGC voltage variable between 0 and 3 V
• Integrated 5th-order matched baseband filters for in-phase (I) and quadrature (Q) signal paths
• Controlled I-to-Q gain balance
• I²C-bus controlled PLL frequency synthesizer
• Low phase noise
• Operation from a 4 MHz crystal (allowing the use of an SMD crystal)
• Five frequency steps from 125 kHz to 2 MHz
• Crystal frequency output to drive the demodulator IC
• Compatible with 5, 3.3 and 2.5 V I²C-bus
• Fully compatible and easy to interface with Philips Semiconductors family of digital satellite demodulators
• +5 V DC supply voltage
• 38-pin high heat dissipation package.

Applications

• Direct Broadcasting Satellite (DBS) QPSK demodulation
• Digital Video Broadcasting (DVB) QPSK demodulation
• BS digital 8PSK demodulation.

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Disclaimers

• General product disclaimer
• Quality and reliability disclaimer