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TEA1094AT 数据表(PDF) 9 Page - NXP Semiconductors |
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TEA1094AT 数据表(HTML) 9 Page - NXP Semiconductors |
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9 / 28 page  1996 Jul 15 9 Philips Semiconductors Product specification Hands free IC TEA1094; TEA1094A LOUDSPEAKER AMPLIFIER: PINS RIN1, RIN2, GAR AND LSP The TEA1094 and TEA1094A have symmetrical inputs for the loudspeaker amplifier with an input resistance of 40 k Ω between RIN1 and RIN2 (2 × 20 kΩ). The input stage can accommodate signals up to 390 mV (RMS) at room temperature for 2% of total harmonic distortion (THD). The gain of the input stage varies according to the mode of the TEA1094 and TEA1094A. In the receive mode, the gain is at its maximum; in the transmit mode, it is at its minimum and in the idle mode, it is halfway between maximum and minimum. Switch-over from one mode to the other is smooth and click-free. The rail-to-rail output stage is designed to power a loudspeaker connected as a single-ended load (between LSP and GND). In the receive mode, the overall gain of the loudspeaker amplifier can be adjusted from 0 dB up to 33 dB to suit specific application requirements. The gain from RIN1 and RIN2 to LSP is proportional to the value of RGAR and equals 18.5 dB with RGAR = 66.5 kΩ. A capacitor connected in parallel with RGAR can be used to provide a first-order low-pass filter. VOLUME CONTROL: PIN VOL The loudspeaker amplifier gain can be adjusted with the potentiometer RVOL. A linear potentiometer can be used to obtain logarithmic control of the gain at the loudspeaker amplifier. Each 950 Ω increase of RVOL results in a gain loss of 3 dB. The maximum gain reduction with the volume control is internally limited to the switching range. DYNAMIC LIMITER: PIN DLC/MUTER The dynamic limiter of the TEA1094 and TEA1094A prevents clipping of the loudspeaker output stage and protects the operation of the circuit when the supply voltage at VBB falls below 2.9 V. Hard clipping of the loudspeaker output stage is prevented by rapidly reducing the gain when the output stage starts to saturate. The time in which gain reduction is effected (clipping attack time) is approximately a few milliseconds. The circuit stays in the reduced gain mode until the peaks of the loudspeaker signals no longer cause saturation. The gain of the loudspeaker amplifier then returns to its normal value within the clipping release time (typically 250 ms). Both attack and release times are proportional to the value of the capacitor CDLC. The total harmonic distortion of the loudspeaker output stage, in reduced gain mode, stays below 5% up to 10 dB (minimum) of input voltage overdrive [providing VRIN is below 390 mV (RMS)]. When the supply voltage drops below an internal threshold voltage of 2.9 V, the gain of the loudspeaker amplifier is rapidly reduced (approximately 1 ms). When the supply voltage exceeds 2.9 V, the gain of the loudspeaker amplifier is increased again. By forcing a level lower than 0.2 V on pin DLC/MUTER, the loudspeaker amplifier is muted and the TEA1094 (TEA1094A) is automatically forced into the transmit mode. Duplex controller SIGNAL AND NOISE ENVELOPE DETECTORS: PINS TSEN, TENV, TNOI, RSEN, RENV AND RNOI The signal envelopes are used to monitor the signal level strength in both channels. The noise envelopes are used to monitor background noise in both channels. The signal and noise envelopes provide inputs for the decision logic. The signal and noise envelope detectors are shown in Fig.7. For the transmit channel, the input signal at MIC is 40 dB amplified to TSEN. For the receive channel, the differential signal between RIN1 and RIN2 is 0 dB amplified to RSEN. The signals from TSEN and RSEN are logarithmically compressed and buffered to TENV and RENV respectively. The sensitivity of the envelope detectors is set with RTSEN and RRSEN. The capacitors connected in series with the two resistors block any DC component and form a first-order high-pass filter. In the basic application, see Fig.13, it is assumed that VMIC = 1 mV (RMS) and VRIN = 100 mV (RMS) nominal and both RTSEN and RRSEN have a value of 10 k Ω. With the value of CTSEN and CRSEN at 100 nF, the cut-off frequency is at 160 Hz. The buffer amplifiers leading the compressed signals to TENV and RENV have a maximum source current of 120 µA and a maximum sink current of 1 µA. Together with the capacitor CTENV and CRENV, the timing of the signal envelope monitors can be set. In the basic application, the value of both capacitors is 470 nF. Because of the logarithmic compression, each 6 dB signal increase means 18 mV increase of the voltage on the envelopes TENV or RENV at room temperature. Thus, timings can be expressed in dB/ms. At room temperature, the 120 µA sourced current corresponds to a maximum rise-slope of the signal envelope of 85 dB/ms. This is sufficient to track normal speech signals. The 1 µA current sunk by TENV or RENV corresponds to a maximum fall-slope of 0.7 dB/ms. This is sufficient for a smooth envelope and also eliminates the effect of echoes on switching behaviour. |
类似零件编号 - TEA1094AT |
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类似说明 - TEA1094AT |
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