Question description:
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According to the MAX7033 datasheet, in pin description, MAX7033 IFIN1 should bypass to AGND with 1500pF, IFIN2 connect to Connect to the output of a 10.7MHz bandpass filter. However, in the EVKIT design, IFIN1 connect to 10.7MHz filteroutput and IFIN2 connect to AGND via 1500pF. Please confirm which connection is correct.
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Answer:
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As indicated in the Functional Diagram on page 9 of the data sheet, the IFIN1 and IFIN2 pins are differential inputs to the Limiting Amplifier chain used to demodulate the ASK signal:
Since these are two differential input pins being fed by a single-ended output from the Intermediate Frequency (IF) filter, either pin can be used as the input. The ‘other’ pin should be tied to ground with a 1500pF capacitor. Thus both the pin description and the Typical Application Circuit are correct—albeit confusing.