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SA636 Datasheet(PDF) 6 Page - NXP Semiconductors |
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SA636 Datasheet(HTML) 6 Page - NXP Semiconductors |
6 / 31 page SA636 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved. Product data sheet Rev. 6 — 5 December 2012 6 of 31 NXP Semiconductors SA636 Low voltage high performance mixer FM IF system 7. Functional description The SA636 is an IF signal processing system suitable for second IF or single conversion systems with input frequency as high as 1 GHz. The bandwidth of the IF amplifier is about 40 MHz with 38 dB of gain from a 50 source. The bandwidth of the limiter is about 28 MHz with about 54 dB of gain from a 50 source. However, the gain/bandwidth distribution is optimized for 10.7 MHz, 330 source applications. The overall system is well-suited to battery operation as well as high performance and high-quality products of all types such as cordless and cellular hand-held phones. The input stage is a Gilbert cell mixer with oscillator. Typical mixer characteristics include a noise figure of 14 dB, conversion gain of 11 dB, and input third-order intercept of 16 dBm. The oscillator will operate in excess of 1 GHz in L/C tank configurations. Hartley or Colpitts circuits can be used up to 100 MHz for crystal configurations. Butler oscillators are recommended for crystal configurations up to 150 MHz. The output of the mixer is internally loaded with a 330 resistor permitting direct connection to a 10.7 MHz ceramic filter for narrowband applications. The input resistance of the limiting IF amplifiers is also 330 . With most 10.7 MHz ceramic filters and many crystal filters, no impedance matching network is necessary. For applications requiring wideband IF filtering, such as DECT, external LC filters are used (see Figure 15). To achieve optimum linearity of the log signal strength indicator, there must be a 6 dBV insertion loss between the first and second IF stages. If the IF filter or interstage network does not cause 6 dBV insertion loss, a fixed or variable resistor can be added between the first IF output (IF_AMP_OUT) and the interstage network. The signal from the second limiting amplifier goes to a Gilbert cell quadrature detector. One port of the Gilbert cell is internally driven by the IF. The other output of the IF is AC-coupled to a tuned quadrature network. This signal, which now has a 90 phase relationship to the internal signal, drives the other port of the multiplier cell. Overall, the IF section has a gain of 90 dB for operation at intermediate frequency at 10.7 MHz. Special care must be given to layout, termination, and interstage loss to avoid instability. The demodulated output (DATA_OUT) of the quadrature is a voltage output. This output is designed to handle a minimum bandwidth of 600 kHz. This is designed to demodulate wideband data, such as in DECT applications. A Received Signal Strength Indicator (RSSI) completes the circuitry. The output range is greater than 90 dB and is temperature compensated. This log signal strength indicator exceeds the criteria for AMPS or TACS cellular telephone, DECT and RCR-28 cordless telephone. This signal drives an internal op amp. The op amp is capable of rail-to-rail output. It can be used for gain, filtering, or second-order temperature compensation of the RSSI, if needed. Remark: dBV = 20log VO/VI. |
Similar Part No. - SA636_15 |
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Similar Description - SA636_15 |
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