Datenblatt-Suchmaschine für elektronische Bauteile |
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TEA1065T Datenblatt(PDF) 10 Page - NXP Semiconductors |
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TEA1065T Datenblatt(HTML) 10 Page - NXP Semiconductors |
10 / 28 page March 1994 10 Philips Semiconductors Product specification Versatile telephone transmission circuit with dialler interface TEA1065 MUTE input When MUTE = HIGH the DTMF input is enabled and the microphone and receiving amplifier inputs are inhibited. When MUTE = LOW or open-circuit the DTMF input is inhibited and the microphone and receiving amplifier inputs are enabled. Switching the MUTE input will cause negligible clicks at the earpiece outputs and on the line. An electrostatic discharge protection diode is connected between pin MUTE and pin VCC (pins 20 and 21). Dual-tone multifrequency input DTMF When the DTMF input is enabled, dialling tones may be sent onto the line. The voltage gain from DTMF to LN is typ. 12.5 dB less than the gain of the microphone amplifier and varies with R7 in the same way as the gain of the microphone amplifier. This means that the tone level at the DTMF input has to be adjusted after setting the gain of the microphone amplifier. When R7 = 68 k Ω the gain is typically 25.5 dB. The signalling tones can be heard in the earpiece at a low level (confidence tone). Receiving amplifiers: IR, QR +, QR− and GAR The receiving amplifier has one input IR and two complementary outputs, QR + (non-inverting) and QR − (inverting). These outputs may be used for single-ended or differential drive, depending on the type and sensitivity of the earpiece used (see Fig.10). Gain from IR to QR + is typically 31 dB with R4 = 100 kΩ, which is sufficient for low-impedance magnetic or dynamic earpieces which are suitable for single-ended drive. By using both outputs (differential drive) the gain is increased by 6 dB. Differential drive can be used when earpiece impedance exceeds 450 Ω as with high impedance dynamic, magnetic or piezoelectric earpieces. The output voltage of the receiving amplifier is specified for continuous-wave drive. The maximum output voltage will be higher under speech conditions where the ratio of peak and RMS value is higher. The gain of the receiving amplifier can be adjusted over a range of −11 dB to +8 dB to suit the sensitivity of the transducer that is used. The gain is proportional to external resistor R4 connected between GAR and QR +. Two external capacitors, C4 = 100 pF and C7 = 1 nF, are necessary to ensure stability. A larger value of C4 may be chosen to obtain a first-order low-pass filter. The “cut-off” frequency corresponds with the time constant R4 × C4. Fig.10 Alternative receiver arrangements: (a) dynamic earpiece with an impedance less than 450 Ω; (b) dynamic earpiece with an impedance more than 450 Ω; (c) magnetic earpiece with an impedance more than 450 Ω, resistor (1) may be connected to prevent distortion (inductive load); (d) piezoelectric earpiece, resistor (2) is required to increase the phase margin (stability with capacitive load). handbook, full pagewidth MBA554 (1) QR − QR + 5 4 VEE 16 QR − QR + 5 4 QR − QR + 5 4 (2) QR − QR + 5 4 (a) (b) (c) (d) |
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