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PCF50732H Datasheet(PDF) 9 Page - NXP Semiconductors |
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PCF50732H Datasheet(HTML) 9 Page - NXP Semiconductors |
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9 / 64 page  1999 May 03 9 Philips Semiconductors Objective specification Baseband and audio interface for GSM PCF50732 8 FUNCTIONAL DESCRIPTION This chapter gives a brief overview of the device. The detailed functional description can be found in the following chapters: Chapter 9 “Baseband CODEC” Chapter 10 “Voice band CODEC” Chapter 11 “Auxiliary functions” Chapter 12 “Control Serial Interface (CSI)” Chapter 13 “Voice band Signal Processor (VSP)”. 8.1 General As low power consumption in mobile telephones is a very important issue, all the circuit parts in the PCF50732 can be powered-on/off either by means of the external signals AUXST, TXON or RXON, or by programming the respective register bits in the Control Serial Interface (CSI). The most important signal for the digital and analog circuit functions in the PCF50732 is the DAC enable signal AUXST, which allows to activate AUXDAC1 (AGC) and AUXDAC2 (AFC), as well as the low-swing master clock input MCLK. AUXST must be active (HIGH) and VDDA must be stable (see also Section 18.1) to allow the master clock to access different circuit parts after a reset (RESET active). AUXDAC1 and AUXDAC2 are only activated if their related power-on bit is set. AUXDAC1 is default off, AUXDAC2 is default on. RESET must be active during at least 3 MCLK cycles, with AUXST active, to ensure a correct initialisation of all the digital circuitry of the PCF50732. Since RESET is asynchronous even small spikes of a few nanoseconds can cause partial resets. For power supply noise interference reduction, a pair of power supply and ground pins are provided for the: • Baseband analog: VDDA(bb)/VSSA(bb) • Voice band analog: VDDA(vb)/VSSA(vb) • Voice band output drivers: VDDA(vbo)/VSSA(vbo) • DC reference voltages and currents: VDDA(ref)/VSSA(ref) • Digital circuitry: VDDD/VSSD. All VSS pins are connected internally. VDDD is the digital supply. VDDA(bb), VDDA(vb), VDDA(vbo), and VDDA(ref) are analog supplies, and are referred to as VDDA throughout this document. These analog supplies must be connected externally. 8.2 Baseband and voice band reference voltages The reference voltage Vref is generated on-chip by a band gap voltage reference circuit and is available at pin Vref. As Vref is used as reference for most of the internal analog circuitry, noise must be kept as low as possible by connecting an external decoupling capacitor at this pin. The voltage at Vref is buffered to generate the baseband and voice band reference voltage Vref as well as internal references for the different functions, such as the auxiliary and the transmit DACs. 9 BASEBAND CODEC The baseband CODEC is a complete interface circuit between the RF part in a mobile communication handset and the digital signal processor. It consists of three parts: • The transmit path, which converts a bitstream to analog quadrature signals for the RF devices • The receive path, which transforms the quadrature signals of the IF chip (I/Q) to digital signals • The digital baseband serial interface, which exchanges baseband data between the PCF50732 and the DSP. The interface also includes signals to power-up and power-down the baseband transmit (TX) and receive (RX) paths. 9.1 Baseband transmit path The baseband transmit path consists of three parts: • GMSK modulator: generation of a Gaussian Minimum Shift Keying (GMSK) signal • 10-bit DACs: digital-to-analog converters for the I and Q components of the GMSK signal • Low-pass filters: analog reconstruction low-pass filters for the output of the DACs. The requirements of the transmit path of a GSM terminal are given by “GSM recommendation 05.05”: • Phase RMS error <5° • Phase peak error <20° • Amplitude error < ±1 dB. Nevertheless the performance of the PCF50732 is far better than these figures indicate; see Section 18.1. |
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Similar Description - PCF50732H |
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