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MC145443B Scheda tecnica(PDF) 4 Page - Motorola, Inc |
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MC145443B Scheda tecnica(HTML) 4 Page - Motorola, Inc |
4 / 12 page MC145442B •MC145443B MOTOROLA 4 TEST INPUT 600 Ω 600 Ω VDD RTLA 20 17 15 16 TEST OUTPUT 4 CDT RxA1 CCDT CFB 0.1 µF 10 FB RxD 5 11 Dout Din TxD Xin 9 8 Xout TLA TxA RxA2 MC145442B MC145443B 0.1 µF 3.579 MHz ± 0.1% Figure 1. AC Characteristics Evaluation Circuit PIN DESCRIPTIONS VDD Positive Power Supply (Pin 6) This pin is normally tied to 5.0 V. VSS Negative Power Supply (Pin 12) This pin is normally tied to 0 V. VAG Analog Ground (Pin 19) Analog ground is internally biased to (VDD – VSS) / 2. This pin must be decoupled by a capacitor from VAG to VSS and a capacitor from VAG to VDD. Analog ground is the common bias line used in the switched capacitor filters, limiter, and slicer in the demodulation circuitry. TLA Transmit Level Adjust (Pin 20) This pin is used to adjust the transmit level. Transmit level adjustment range is typically from –12 dBm to –9 dBm. (See Applications Information.) TxD Transmit Data (Pin 11) Binary information is input to the transmit data pin. Data entered for transmission is modulated using FSK techniques. A logic high input level represents a mark and a logic low represents a space (see Table 1). TxA Transmit Carrier (Pin 17) This is the output of the line driver amplifier. The transmit carrier is the digitally synthesized sine wave output of the modulator derived from a crystal oscillator reference. When a 3.579 MHz crystal is used the frequency outputs shown in Table 1 apply. (See Applications Information.) Table 1. Bell 103 and CCITT V.21 Frequency Characteristics Originate Mode Answer Mode Data Transmit Receive Transmit Receive Bell 103 (MC145443B) Space 1070 Hz 2025 Hz 2025 Hz 1070 Hz Mark 1270 Hz 2225 Hz 2225 Hz 1270 Hz CCITT V.21 (MC145442B) Space 1180 Hz 1850 Hz 1850 Hz 1180 Hz Mark 980 Hz 1650 Hz 1650 Hz 980 Hz NOTE: Actual frequencies may be ±5 Hz assuming 3.579545 MHz crystal is used. 15 dB/OCTAVE 256 64 16 3.4 4 2 0 0 –20 –25 –55 –60 MAXIMUM LEVEL OF OUT–OF–BAND ENERGY RELATIVE TO THE TRANSMIT CARRIER LEVEL INTO 600 Ω (kHz) Figure 2. Out–of–Band Energy ExI External Input (Pin 18) The external input is the non–inverting input to the line driver. It is provided to combine an auxiliary audio signal or speech signal to the phone line using the line driver. This pin should be connected to VAG if not used. The average level must be the same as VAG to maintain proper operation. (See Applications Information.) DSI Driver Summing Input (Pin 1) The driver summing input may be used to connect an ex- ternal signal, such as a DTMF dialer, to the phone line. A series resistor, RDSI, is needed to define the voltage gain AV (see Applications Information and Figure 6). When ap- plying a signal to the DSI pin, the modulator should be squelched by bringing SQT (pin 14) to a logic high level. The voltage gain, AV, is calculated by the formula AV = –Rf/RDSI (where Rf ≈ 20 kΩ). For example, a 20 kΩ resistor for RDSI will provide unity gain (AV = –20 kΩ/20 kΩ = –1). This pin must be left open if not used. RxD Receive Data (Pin 6) The receive data output pin presents the digital binary data resulting from the demodulation of the receive carrier. If no carrier is present, CD high, the receive data output (RxD) is clamped high. |
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