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TEA1111AT Arkusz danych(PDF) 9 Page - NXP Semiconductors |
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TEA1111AT Arkusz danych(HTML) 9 Page - NXP Semiconductors |
9 / 24 page 1999 Nov 22 9 Philips Semiconductors Product specification Speech circuit with dialler interface, regulated supply and earpiece volume control TEA1111A Transmit stage (pins MIC+, MIC − and DTMF) MICROPHONE AMPLIFIER (PINS MIC+ AND MIC −) The TEA1111A has symmetrical microphone inputs. The input impedance between pins MIC+ and MIC − is 68 k Ω (2 × 34 kΩ). The voltage gain from pins MIC+/MIC− to pin LN is set at 44.2 dB (typical) at 600 Ω line load. Automatic gain control is provided on this amplifier for line loss compensation. DTMF AMPLIFIER (PIN DTMF) When the DTMF amplifier is enabled, dialling tones may be sent on line. These tones are also sent to the receive output QR at a low level (confidence tone), the level is controlled by pin VCI. The TEA1111A has an asymmetrical DTMF input. The input impedance between DTMF and VEE is 20 kΩ and it is biased at VEE. The voltage gain from pin DTMF to pin LN is set at 25.9 dB. Automatic gain control has no effect on the DTMF amplifier. Receiving stage (pins IR, GAR, QR and VCI) The receive part consists of an earpiece amplifier and a volume control block. EARPIECE AMPLIFIER The earpiece amplifier has one input (IR) and one output (QR). The input impedance between pin IR and pin VEE is 22 k Ω. When pin VCI is tied to VEE, the voltage gain from pin IR to pin QR is set at 27.4 dB (typical) which reduces the attenuation of the receive signal by the anti-sidetone network from 32 dB to 4.6 dB. The gain can be decreased by connecting an external resistor RGARext between pins GAR and QR; the adjustment range is 6 dB. Two external capacitors CGAR (connected between pins GAR and QR) and CGARS (connected between pins GAR and VEE) ensure stability. Capacitor CGAR provides a first-order low-pass filter. The cut-off frequency corresponds to the time constant CGAR × RGARint. Where RGARint is the internal resistor (123 kΩ typical) which sets the gain. The relationship CGARS =10 × CGAR must be complied with to ensure stability. The output voltage of the earpiece 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. VOLUME CONTROL (PIN VCI) A positive DC voltage applied to pin VCI allows the gain of the earpiece amplifier to be increased in steps of 4.85 dB. The volume control range is 27.4 to 41.9 dB (14.5 dB typical). A proportional voltage decoder at pin VCI defines a gain of 27.4 dB when VVCI equals VEE and a gain of 41.9 dB when VVCI equals VDD. The intermediate steps correspond to: and . Automatic gain control (pin AGC) The TEA1111A performs automatic line loss compensation. The automatic gain control varies the gain of the microphone amplifier and the gain of the receive amplifier in accordance with the DC line current. The control range is 6.0 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 IC 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) The mute function performs the switching between the speech mode and the dialling mode. When MUTE is LOW, the DTMF input is enabled and the microphone and receive amplifier inputs are disabled. In this mode, the DTMF tones are sent to the receive output at a low level (confidence tone). When MUTE is HIGH, the microphone and receiving amplifiers inputs are enabled while the DTMF input is disabled. The MUTE input is provided with an internal pull-up current source to VDD. V VCI 1 3 --- VDD = V VCI 2 3 --- VDD = |
Podobny numer części - TEA1111AT |
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Podobny opis - TEA1111AT |
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