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TEA1062T Scheda tecnica(PDF) 5 Page - NXP Semiconductors |
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TEA1062T Scheda tecnica(HTML) 5 Page - NXP Semiconductors |
5 / 28 page 1997 Sep 03 5 Philips Semiconductors Product specification Low voltage transmission circuits with dialler interface TEA1062; TEA1062A FUNCTIONAL DESCRIPTION Supplies VCC, LN, SLPE, REG and STAB Power for the IC and its peripheral circuits is usually obtained from the telephone line. The supply voltage is derived from the line via a dropping resistor and regulated by the IC. The supply voltage VCC may also be used to supply external circuits e.g. dialling and control circuits. Decoupling of the supply voltage is performed by a capacitor between VCC and VEE. The internal voltage regulator is decoupled by a capacitor between REG and VEE. The DC current flowing into the set is determined by the exchange supply voltage Vexch, the feeding bridge resistance Rexch and the DC resistance of the telephone line Rline. The circuit has an internal current stabilizer operating at a level determined by a 3.6 k Ω resistor connected between STAB and VEE (see Fig.9). When the line current (Iline) is more than 0.5 mA greater than the sum of the IC supply current (ICC) and the current drawn by the peripheral circuitry connected to VCC (Ip) the excess current is shunted to VEE via LN. The regulated voltage on the line terminal (VLN) can be calculated as: VLN =Vref +ISLPE × R9 VLN =Vref + {(Iline − ICC − 0.5 × 10−3 A) − Ip} × R9 Vref is an internally generated temperature compensated reference voltage of 3.7 V and R9 is an external resistor connected between SLPE and VEE. In normal use the value of R9 would be 20 Ω. Changing the value of R9 will also affect microphone gain, DTMF gain, gain control characteristics, sidetone level, maximum output swing on LN and the DC characteristics (especially at the lower voltages). Under normal conditions, when ISLPE >> ICC + 0.5 mA + Ip, the static behaviour of the circuit is that of a 3.7 V regulator diode with an internal resistance equal to that of R9. In the audio frequency range the dynamic impedance is largely determined by R1. Fig.3 shows the equivalent impedance of the circuit. At line currents below 9 mA the internal reference voltage is automatically adjusted to a lower value (typically 1.6 V at 1 mA). This means that more sets can be operated in parallel with DC line voltages (excluding the polarity guard) down to an absolute minimum voltage of 1.6 V. At line currents below 9 mA the circuit has limited sending and receiving levels. The internal reference voltage can be adjusted by means of an external resistor (RVA). This resistor when connected between LN and REG will decrease the internal reference voltage and when connected between REG and SLPE will increase the internal reference voltage. Current (Ip) available from VCC for peripheral circuits depends on the external components used. Fig.10 shows this current for VCC > 2.2 V. If MUTE is LOW (TEA1062) or MUTE is HIGH (TEA1062A) when the receiving amplifier is driven, the available current is further reduced. Current availability can be increased by connecting the supply IC (TEA1081) in parallel with R1 as shown in Fig.19 and Fig.20, or by increasing the DC line voltage by means of an external resistor (RVA) connected between REG and SLPE (Fig.18). Fig.3 Equivalent impedance circuit. Leq =C3 × R9 × Rp. Rp = 16.2 kΩ. handbook, halfpage REG V EE VCC LN MBA454 Leq R p R1 V ref R9 20 Ω C3 4.7 µF C1 100 µF |
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