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TEA1112 Datasheet(PDF) 6 Page - NXP Semiconductors |
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TEA1112 Datasheet(HTML) 6 Page - NXP Semiconductors |
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6 / 20 page  1997 Mar 26 6 Philips Semiconductors Product specification Low voltage versatile telephone transmission circuits with dialler interface TEA1112; TEA1112A 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 sending and receiving 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.8. LED supply (pin ILED) The TEA1112; TEA1112A give an on-hook/off-hook status indication. This is achieved by a current made available to drive an LED connected between pins ILED and LN. In the low voltage area, which corresponds to low line current conditions, no current is available for this LED. Fig.5 Reference voltage adjustment by RVA. (1) Influence of RVA on Vref. (2) Vref without influence of RVA. handbook, halfpage 6.0 Vref (V) 3.0 4.0 (1) (2) 5.0 RVA (Ω) MGD176 105 104 106 107 For line currents higher than a threshold, ILEDstart, the ILED current increases proportionally to the line current (with a ratio of one third). The ILED current is internally limited to 19.5 mA (see Fig.9). If no LED device is used in the application, the ILED pin should be shorted to pin SLPE. For 17 mA < Iline < 77 mA: This LED driver is referenced to SLPE. Consequently, all the ILED supply current will flow through the RSLPE resistor. The AGC characteristics are not disturbed (see Fig.4). Microphone amplifier (pins MIC+, MIC − and GAS) The TEA1112; TEA1112A have symmetrical microphone inputs. The input impedance between pins MIC+ and MIC − is 64 kΩ (2 × 32 kΩ). The voltage gain from pins MIC+/MIC − to pin LN is set at 51.8 dB (typ). The gain can be decreased by connecting an external resistor RGAS between pins GAS and REG. The adjustment range is 13 dB. A capacitor CGAS connected between pins GAS and REG can be used to provide a first-order low-pass filter. The cut-off frequency corresponds to the time constant CGAS × (RGASint // RGAS). RGASint is the internal resistor which sets the gain with a typical value of 69 k Ω. Automatic gain control is provided on this amplifier for line loss compensation. Microphone mute (pin MMUTE; TEA1112) The microphone amplifier can be disabled by activating the microphone mute function. When MMUTE is LOW, the normal speech mode is entered, depending on the level on MUTE (see Table 1). When MMUTE is HIGH, the microphone amplifier inputs are disabled while the DTMF input is enabled (no confidence tone is provided). The voltage gain between LN and MIC+/MIC − is attenuated; the gain reduction is 80 dB (typ). Microphone mute (pin MMUTE; TEA1112A) The microphone amplifier can be disabled by activating the microphone mute function. When MMUTE is LOW, the microphone amplifier inputs are disabled while the DTMF input is enabled (no confidence tone is provided). The voltage gain between LN and MIC+/MIC − is attenuated; the gain reduction is 80 dB (typ). When MMUTE is HIGH, the normal speech mode is entered, depending on the level on MUTE (see Table 1). I LED I line 17 – 3 ---------------------- = |
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Similar Description - TEA1112 |
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