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TEA5777 Datenblatt(PDF) 11 Page - NXP Semiconductors |
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TEA5777 Datenblatt(HTML) 11 Page - NXP Semiconductors |
11 / 48 page TEA5777_1 © Koninklijke Philips Electronics N.V. 2006. All rights reserved. Product data sheet Rev. 01 — 11 April 2006 10 of 47 Philips Semiconductors TEA5777 Low-power AM/FM stereo radio for handheld applications Bus communication: • Bus communication takes place via the I2C-bus or the 3-wire bus protocol. Selection of the bus mode is done by hardware programming via pin BUSMODE • 4-bit ADC level information, 1-bit IF counter and mono or stereo indication (in FM mode) can be read via the bus. Alternatively, the mono or stereo and the IF in-window indication can be obtained via silent readout via the bus lines CLOCK and DATA 8.1 AM radio part 8.1.1 AM RF amplifier The AM input pin AMRFIN has a (selectable) high-impedance input. The input is intended to be connected to the top of a tuned circuit. The input impedance is determined by the LNA gain (bit LNA) and the value of the LNA feedback resistor (bit RFB). For large RF input signals, the RF AGC reduces the input signal level to the AM front end in order to prevent overloading. The required AM RF AGC time constant is created by means of an internal current source and the capacitor connected to pin PILDET/AMRFAGC. During search operation the response time of this RF AGC circuit can be speeded up via the bus control by bit AGCRF. 8.1.2 Tuning AM antenna circuit The tuning capacitor for the AM antenna circuit has been integrated by means of a capacitor bank (C-bank) and the tuning frequency can be programmed in discrete steps via the bus. No external varactor diode is required. In order to match the capacitor bank to the external AM antenna coil, a provision has been made to electronically align the IC to the AM antenna. For this bit CALLIGN has to be set to logic 1 and the corresponding bits C[6:0] have to be programmed. After this alignment bit CALLIGN should be set to logic 0 again to freeze the alignment capacitor value and to enable the control over the main capacitor bank again. For more details on the alignment, see Section 13.1 and the application note. For LW mode an external capacitor needs to be added in parallel to the LW coil. 8.1.3 AM I/Q mixer AM quadrature mixers, in an orthogonal architecture, convert AM RF signals to the internal fIF = 21 kHz. The mixer architecture provides inherent image rejection. 8.1.4 AM VCO The fully integrated VCO provides the local oscillator signals for the AM quadrature mixers. No external components are required. The internal VCO frequency ranges from 4 MHz to 14 MHz and the proper divider ratio is chosen by selecting the MW or LW band via the bus control bit MWLW. Programming of the VCO is done: • For MW: fVCO = 8 × (fRF ± fIF) • For LW: fVCO = 32 × (fRF ± fIF) |
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