PDF U4030B Data sheet ( Hoja de datos )

Número de pieza	U4030B
Descripción	Telephone Speech Circuit
Fabricantes	TEMIC Semiconductors
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No Preview Available ! www.DataSheet4U.com Telephone Speech Circuit U4030B Description The U4030B is an electronic speech circuit for standard and feature telephones. It replaces the hybrid transformer, earphone and microphone interface and the supply voltage generation for external components, e.g. dialer or microcomputers. Using the U4030B in telephone circuit designs can improve transmission quality and results in cost savings through shorter and more flexible design procedures. It reduces the amount of external components needed. The U4030B uses TEMIC’s reliable bipolar technology and is offered in a SO20 package. Features D Microphone amplifier with – Symmetrical input – Privacy function – Anticlipping D Built in ear protection D Power down input D Mute input D DTMF interface D Low line impedance during pulse dialing Benefits D Independent adjustment of – Transmission gain – Receiving gain – Sidetone suppression – Frequency response D Low-impedance supply voltage for all external blocks D Supply voltage for an electret microphone Applications D Standard telephone D Fax machine D Answering machine D Cordless telephone Block Diagram 10 DTMF PRIV MIC1 MIC2 16 12 13 GT MICO 11 9 – + ST 5 + – TXA GR RECO 67 +– Ear protection REC.ATT. 4 CK Limiter 3 CLIM Mute 8 MUTE 17 PD Power supply U 4030 B 14 GND 18 1 SWAMP VM 15 VL 19 RDC 2 VC 20 VD Figure 1. Ordering Information 93 7618 e Extended Type Number U4030B-AFL U4030B-AFLG3 Package SO20 SO20 Remarks Taped and reeled Rev. A2, 27-Jan-98 1 (14) 1 page U4030B Transmit Output Amplifier The output signal of the microphone and DTMF preamplifier is internally coupled to a second amplifier ( TXA) which is used to modulate a controlled current source. Assuming a termination of 600 W at a line, the gain from MICO to VL is typically 15.6 dB. Receive Amplifier The receive signal is taken from line via capacitor CCK. A resistive attenuator ( –32 dB ) sets the appropriate input level for the following output amplifier. The input impedance at Pin 4 is typically 80 kW. Voltage gain is: GR = 20 log ( Vear / VL ) dB = –32 dB + 20 log [ ( RR1 / RR2 ) + 1 ] dB = +1.8 dB The adjustment range for receive gain GR is typically –4 dB to + 8 dB. The built-in ear protection limits the output swing at Pin 7 to 2.4 Vpp ( VD > 4 V). For high receive gain, the maximum undistorted output level might not be sufficient due to clipping by ear protection. Sidetone The amplified microphone signal is available at the input of the sidetone loop, MICO. The loop consists of a transmit amplifier ( transconductance STX ), the impedance at line, receive attenuator ( gain) and the side- tone network ( figure 7 ). The sidetone cancellation is achieved by comparing a part of the line signal with the output of the sidetone network ( VST → VR). Assuming a real impedance of the tele- phone ( RTel ) the optimum sidetone network can be calculated: a = ( STX RAPP G ) / ( 1 – STX RAPP G ) ZNW = STX R G ZLine Adjustment to the sensitivities of the handset can be done independently from the sidetone network because receive and transmit gain are set outside of the sidetone loop. Power Down (PD) The speech circuit is switched low ohmic by selecting a high level at PD during the pulse dialling. The voltage drop across the IC will be typically 1.5 V. During this time the capacitor CVD will not be discharged, because an internal power down switches off all internal amplifiers. In order to avoid cracks, it is recommended to activate power down while sending the dial pulses ( figure 8 ). R aR ZNW MICO Mic. + V ST – VR G = 1/40 VL VH STX = 18.8 mS RTEL ZL Figure 7. Schematic of the sidetone 93 7624 e Rev. A2, 27-Jan-98 5 (14) 5 Page DTMF 470 n VC 10m CVM 10m CR RR2 2.2 m 680 CLIM 470 n RR1 33 k CRNW2 RNW2 100 n 18 k RNW3 2.7 k CRNW3 100 n C 470 n VGEN RNW4 390 CRNW4 53 n VEAR U 4030 B VM VD VC RDC CLIM SWAMP CK PD ST PRIV GR VL RECO GND MUTE MICO DTMF RS1 MIC2 MIC1 CS 12 k CRECO 10 m ROUT 150 ZEAR 68 n CK 68 n RDC 10 CVD 1000 m RSWAMP 68 15 V 68 n RS2 430 CS 2.2 m MIC1 ZM 68 n MIC2 RIMP 1k 47 m RL 600 100 m IL VGEN 11 Page

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Número de pieza	Descripción	Fabricantes
U4030B	Telephone Speech Circuit	TEMIC Semiconductors

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