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TEA1112A Datasheet(PDF) 7 Page - NXP Semiconductors |
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TEA1112A Datasheet(HTML) 7 Page - NXP Semiconductors |
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7 / 20 page  1997 Mar 26 7 Philips Semiconductors Product specification Low voltage versatile telephone transmission circuits with dialler interface TEA1112; TEA1112A Receiving amplifier (pins IR, GAR and QR) The receiving amplifier has one input (IR) and one output (QR). The input impedance between pin IR and pin VEE is 20 k Ω. The voltage gain from pin IR to pin QR is set at 31.2 dB (typ). The gain can be decreased by connecting an external resistor RGAR between pins GAR and QR; the adjustment range is 12 dB. Two external capacitors CGAR (connected between GAR and QR) and CGARS (connected between GAR and VEE) ensure stability. The CGAR capacitor provides a first-order low-pass filter. The cut-off frequency corresponds to the time constant CGAR × (RGARint // RGAR). RGARint is the internal resistor which sets the gain with a typical value of 100 k Ω. The relationship CGARS =10 × CGAR must be fulfilled to ensure stability. The output voltage of the receiving amplifier is specified for continuous wave drive. The maximum output swing depends on the DC line voltage, the RCC resistor, the ICC current consumption of the circuit, the Ip current consumption of the peripheral circuits and the load impedance. Automatic gain control is provided on this amplifier for line loss compensation. Automatic gain control (pin AGC) The TEA1112; TEA1112A perform automatic line loss compensation. The automatic gain control varies the gain of the microphone amplifier and the gain of the receiving amplifier in accordance with the DC line current. The control range is 5.8 dB (which corresponds approximately to a line length of 5 km for a 0.5 mm diameter twisted-pair copper cable with a DC resistance of 176 Ω/km and an average attenuation of 1.2 dB/km). The ICs can be used with different configurations of feeding bridge (supply voltage and bridge resistance) by connecting an external resistor RAGC between pins AGC and VEE. This resistor enables the Istart and Istop line currents to be increased (the ratio between Istart and Istop is not affected by the resistor). The AGC function is disabled when pin AGC is left open-circuit. Mute function (pin MUTE; TEA1112) The mute function performs the switching action between the speech mode and the dialling mode. When MUTE is LOW or open-circuit, the microphone and receiving amplifiers inputs are enabled while the DTMF input is disabled, depending on the MMUTE level (see Table 1). When MUTE is HIGH, the DTMF input is enabled and the microphone and receiving amplifiers inputs are disabled. Mute function (pin MUTE; TEA1112A) The mute function performs the switching between the speech mode and the dialling mode. When MUTE is LOW or open-circuit, the DTMF input is enabled and the microphone and receiving amplifiers inputs are disabled. When MUTE is HIGH, the microphone and receiving amplifiers inputs are enabled while the DTMF input is disabled, depending on the MMUTE level (see Table 1). DTMF amplifier (pin DTMF) When the DTMF amplifier is enabled, dialling tones may be sent on line. These tones can be heard in the earpiece at a low level (confidence tone). The TEA1112; TEA1112A have an asymmetrical DTMF input. The input impedance between DTMF and VEE is 20 k Ω. The voltage gain from pin DTMF to pin LN is 25.5 dB. When an external resistor is connected between pins REG and GAS to decrease the microphone gain, the DTMF gain varies in the same way (the DTMF gain is 26.3 dB lower than the microphone gain with no AGC control). The automatic gain control has no effect on the DTMF amplifier. |
Similar Part No. - TEA1112A |
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Similar Description - TEA1112A |
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