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TEA1118AT Datasheet(PDF) 10 Page - NXP Semiconductors |
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TEA1118AT Datasheet(HTML) 10 Page - NXP Semiconductors |
10 / 24 page 1997 Jul 14 10 Philips Semiconductors Product specification Versatile cordless transmisssion circuit TEA1118; TEA1118A Automatic Gain Control (pin AGC) The TEA1118 and TEA1118A perform automatic line loss compensation. The automatic gain control varies the gain of the transmit amplifier and the gain of the receive 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. DTMF amplifier (pin DTMF; TEA1118A only) 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 TEA1118A has an asymmetrical DTMF input. The input impedance between DTMF and VEE is 20 kΩ. The voltage gain from pin DTMF to pin LN is 17.4 dB. The automatic gain control has no effect on the DTMF amplifier. Mute function (pin MUTE; TEA1118A only) The mute function performs the switching action between the speech mode and the dialling mode. When MUTE is LOW or open-circuit, the transmit and receive amplifiers inputs are enabled while the DTMF input is disabled, depending on the TMUTE level. When MUTE is HIGH, the DTMF input is enabled and the transmit and receive amplifiers inputs are disabled. Sidetone suppression The TEA1118 and TEA1118A anti-sidetone network comprising RCC//Zline, Rast1, Rast2, Rast3, RSLPE and Zbal (see Fig.12) suppresses the transmitted signal in the earpiece. Maximum compensation is obtained when the following conditions are fulfilled: The scale factor k is chosen to meet the compatibility with a standard capacitor from the E6 or E12 range for Zbal. In practice, Zline varies considerably with the line type and the line length. Therefore, the value chosen for Zbal should be for an average line length which gives satisfactory sidetone suppression with short and long lines. The suppression also depends on the accuracy of the match between Zbal and the impedance of the average line. The anti-sidetone network for the TEA1118 and TEA1118A (as shown in Fig.16) attenuates the receive signal from the line by 32 dB before it enters the receive amplifier. The attenuation is almost constant over the whole audio frequency range. A Wheatstone bridge configuration (see Fig.13) may also be used. More information on the balancing of an anti-sidetone bridge can be obtained in our publication “Applications Handbook for Wired Telecom Systems, IC03b”, order number 9397 750 00811. R SLPE R ast1 × R CC R ast2 R ast3 + () × = k R ast2 R ast3 R SLPE + () × [] R ast1 R SLPE × () ----------------------------------------------------------------------- = Z bal kZ line × = MUTE and TMUTE levels for different modes (TEA1118A only) Table 1 Required MUTE and TMUTE levels to enable the different possible modes Note 1. X = don’t care. MODE CHANNEL MUTE TMUTE TRANSMIT RECEIVE DTMF CONFIDENCE TONE Speech on on off off LOW LOW DTMF dialling off off on on HIGH X(1) Transmit mute off on on off LOW HIGH |
Similar Part No. - TEA1118AT |
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Similar Description - TEA1118AT |
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