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TEA1118M Datasheet(PDF) 7 Page - NXP Semiconductors |
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TEA1118M Datasheet(HTML) 7 Page - NXP Semiconductors |
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7 / 24 page  1997 Jul 14 7 Philips Semiconductors Product specification Versatile cordless transmisssion circuit TEA1118; TEA1118A FUNCTIONAL DESCRIPTION All data given in this chapter are typical values, except when otherwise specified. Supplies (pins LN, SLPE, VCC and REG) The supply for the TEA1118 and TEA1118A and their peripherals is obtained from the telephone line. The ICs generate a stabilized reference voltage (Vref) between pins LN and SLPE. This reference voltage is equal to 3.35 V, is temperature compensated and can be adjusted by means of an external resistor (RVA). It can be increased by connecting the RVA resistor between pins REG and SLPE (see Fig.11), or decreased by connecting the RVA resistor between pins REG and LN. The voltage at pin REG is used by the internal regulator to generate the stabilized reference voltage and is decoupled by a capacitor (CREG) which is connected to VEE. This capacitor, converted into an equivalent inductance (see Section “Set impedance”), realizes the set impedance conversion from its DC value (RSLPE) to its AC value (RCC in the audio-frequency range). The voltage at pin SLPE is proportional to the line current. Figure 7 illustrates the supply configuration. The ICs regulate the line voltage at pin LN, and it can be calculated as follows: VLN =Vref +RSLPE × ISLPE ISLPE =Iline − ICC − IP − I* = Ish where: Iline: line current ICC: current consumption of the IC IP: supply current for peripheral circuits I*: current consumed between LN and VEE Ish: the excess line current shunted to SLPE (and VEE) via LN. The preferred value for RSLPE is 20 Ω. Changing RSLPE will affect more than the DC characteristics; it also influences the transmit gain and the DTMF gain (TEA1118A only), the gain control characteristics, the sidetone level and the maximum output swing on the line. The internal circuitry of the TEA1118 and TEA1118A is supplied from pin VCC. This voltage supply is derived from the line voltage by means of a resistor (RCC) and must be decoupled by a capacitor CVCC. It may also be used to supply peripheral circuits such as dialling or control circuits. The VCC voltage depends on the current consumed by the IC and the peripheral circuits as shown by the formula (see also Figs 8 and 9). RCCint is the internal equivalent resistance of the voltage supply point, and Irec is the current consumed by the output stage of the earpiece amplifier. VCC =VCC0 − RCCint × (IP − Irec) VCC0 =VLN − RCC × ICC The DC line current flowing into the set is determined by the exchange supply voltage (Vexch), the feeding bridge resistance (Rexch), the DC resistance of the telephone line (Rline) and the reference voltage (Vref). With line currents below 7.5 mA, the internal reference voltage (generating Vref) is automatically adjusted to a lower value. This means that more sets can operate in parallel with DC line voltages (excluding the polarity guard) down to an absolute minimum voltage of 1.6 V. At currents below 7.5 mA, the circuit has limited transmit and receive levels. This is called the low voltage area. Set impedance In the audio frequency range, the dynamic impedance is mainly determined by the RCC resistor. The equivalent impedance of the circuits is illustrated in Fig.10. Transmit amplifier (pins TX+, TX − and GAT) The TEA1118 and TEA1118A have symmetrical transmit inputs. The input impedance between pins TX+ and TX − is equal to 62.5 k Ω; the input impedance between pins TX+/TX − and VEE is equal 36.5 kΩ. The voltage gain from pins TX+/TX − to pin LN is set at 11.3 dB. Automatic gain control is provided on this amplifier for line loss compensation. The gain of the TEA1118 can be decreased by connecting an external resistor RGAT between pins GAT and REG. The adjustment range is equal to 6 dB. A capacitor CGAT connected between pins GAT and REG can be used to provide a first-order low-pass filter. The cut-off frequency corresponds to the time constant CGAT ×(RGATint // RGAT). RGATint is the internal resistor which sets the gain with a typical value of 27 k Ω. Transmit mute (pin TMUTE; TEA1118A only) The transmit amplifier can be disabled by activating the transmit mute function. When TMUTE is LOW, the normal speech mode is entered, depending on the level on MUTE. When TMUTE is HIGH, the transmit amplifier inputs are disabled while the DTMF input is enabled (no confidence tone is provided). The voltage gain between LN and TX+/TX − is attenuated; the gain reduction is 80 dB. |
Similar Part No. - TEA1118M |
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Similar Description - TEA1118M |
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