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| FM-Demodulator for SAT TV with Switchable Input TDA 6142-5X Preliminary Data Bipolar IC Features q High input sensitivity results in excellent carrier/noise behaviour q Reduced noise bandwidth for the prescaler with 480-MHz LC circuit q Limitation of the prescaler's internal bandwidth to 960 MHz q Due to the LC circuit improvement stability against oscillations q Interferences reduced by damping higher frequencies with LC circuit q Switch for double SAW filter input integrated. P-DSO-20-1 Type TDA 6142-5X Ordering Code Q67000-A5173 Package P-DSO-20-1 (SMD) Amplifier and IF demodulator for satellite applications, consisting of: four-stage limiter amplifier with selection circuit and input selector for two IF-inputs, each with a base stage; divider by 4; video amplifier; AGC regulator; AFC-output with adjustable steepness; polarity reversal of the video signal. Application Used in indoor units. Semiconductor Group 1 04.95 TDA 6142-5X Pin Configuration (top view) P-DSO-20-1 Semiconductor Group 2 TDA 6142-5X Pin Definitions and Functions Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Function Connection for parallel resonance circuit Connection for parallel resonance circuit AGC-control voltage output AGC-threshold adjust Demodulator tank circuit Demodulator tank circuit Ground AFC-preamplifier output AFC-low pass filter and feedback point for AFC-sensitivity setting AFC-output to A/D-converter and AFC-low pass filter Video output Video polarity switch input, positive/negative modulation IF-reference input 1 IF-input 1, e.g. f = 27 MHz Reference voltage output IF-input select for IF-input 1 or 2 IF-reference input 2 IF-input 2, e.g. f = 18 MHz Supply voltage 5 V AGC-low pass filter Semiconductor Group 3 TDA 6142-5X Block Diagram Semiconductor Group 4 TDA 6142-5X Circuit Description The FM modulated satellite IF signal is fed to both low-ohm symmetrical inputs of the limiting amplifier via a SAW filter with two symmetrical outputs and different bandwidths. With an external DC voltage at pin 16 of the IF input selector, an IF-input-signal can be switched through the IFinput 1 or IF-input 2. By high frequency blocking of the limiting amplifier's symmetrical inputs, asymmetrical operation is also possible, but with increased noise. An external selection circuit in the penultimate amplifier stage produces good selectivity of the limiting amplifier and thus provides a better suppression of harmonics. The output signal of the amplifier is fed to a divider, which splits the frequency into four. The signal is then led to a quadrature demodulator, once directly, and once with phase shift produced by an external phase-shifting circuit. The demodulated video signal is amplified and is available at the video output. The polarity of this signal can be inverted by a DC voltage applied from outside to the polarity reversal input. The demodulated video signal is likewise used for AFC regulation. It is fed via a preamplifier to an inverting OP amplifier at which an internal reference voltage is present. Any frequency offset appears as a varying DC voltage, which can in turn be led to an external A/D converter. The AFC S-curve and the amplification of the OPs can be adjusted via an external resistor. The information for the field strength of the FM modulated satellite IF signal is present as DC voltage at both the AGC output and the AGC low pass filter. A pot can be used to change the AGC threshold. The IF stage of the satellite tuner , or a prestage, can be regulated via the AGC output by amplification. Semiconductor Group 5 TDA 6142-5X Absolute Maximum Ratings TA = 0 to 70 C Parameter Supply voltage Selectivity circuit AGC-control voltage output AGC-threshold input Demodulator LC-circuit input AFC-amplifier AFC-low pass filter AFC-output Video output Video P/N-switching IF-inputs Reference voltage IF-input selector AGC-low pass filter Junction temperature Storage temperature Thermal resistance Operating Range Supply voltage Input frequency range Ambient temperature during operation Symbol min. Limit Values max. 6 6 13 2 3 6 5 5 5 6 3 5 5 5 150 - 40 125 125 V V V V V V V V V V V V V V C C K/W Open collector 0 0 1 0.3 - 0.3 0 0 0 1 - 0.3 0.3 0.3 0.3 - 0.3 Unit Test Condition VS V1, 2 V3 V4 V5, 6 V8 V9 V10 V11 V12 V13, 14, 17, 18 V15 V16 V20 Tj Tstg Rth SA VS f15 TA 4.5 360 0 5.5 560 70 V MHz C Semiconductor Group 6 TDA 6142-5X Characteristics TA = 25 C; VS = 5 V 10 % (test circuit 1) Parameter Power consumption Input Sensitivity IF-input Symbol min. Limit Values typ. 40 max. 50 mA 30 Unit Test Condition IS aIFin - 65 3 dBm f13, 14 & 17, 18 = 480 MHz IF-Input Switching IF-input 1 IF-input 2 Video Output Video voltage (f = 13.5 MHz) Distortion factor Signal/noise ratio Video P/N-Switching Positive polarity Input current Negative polarity Input current AGC-Current V16 V16 3.2 0 5 2.8 V V V11 THD S/N 400 <1 70 600 mV % dB V12 I12 H V12 I12 L 3.5 0 5 50 1 - 50 V A V A aIFin = - 28 dBm aIFin = - 18 dBm I3 I3 10 500 A A V3 = 8 V; Resistor at Pin 4 = 4.7 k AFC-Voltage (Open-collector current limited) fIFin = 480 MHz fIFin = 440 MHz fIFin = 520 MHz V10 V10 V10 2.4 VS - 0.9 V 0.05 V V V R2/R1 = 7 R2/R1 = 7 Semiconductor Group 7 TDA 6142-5X Test Circuit 1 Semiconductor Group 8 TDA 6142-5X Application Circuit Semiconductor Group 9 TDA 6142-5X Diagram 1 Diagram 2 Semiconductor Group 10 |
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