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AD8349 IQ inputs

Question asked by cweston on Nov 9, 2015
Latest reply on Nov 13, 2015 by THA

I had a question regarding the IBBP/IBBN and QBBP/QBBN input levels as the datasheet seems to contradict itself. The pin descriptions on page six (or page 15) state that the differential inputs:

  • Must be biased to 400 mV
  • 600 mV p-p on each pin
  • 1.2 V p-p differential drive

 

In order to achieve all three requirements I would think IBBP and QBBP would swing from 0.4V to 1V and IBBN and QBBN would swing from -0.2V and 0.4V. This would produce a 1.2V p-p (1-(-0.2) = 1.2) drive biased to 400 mV. However, this can't be the case since the absolute maximum range for the inputs is 0-2.5V.

 

If both inputs were centered around 400 mV and swung from 100 mV to 700 mV I would think the differential drive would only be 600 mV. Any clarification would help. Thanks.

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