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AD9959 evaluation board control

Question asked by bbraverm on Apr 22, 2014
Latest reply on Apr 23, 2014 by bbraverm

Hi everyone,


I have a question about the AD9959 evaluation board (i.e. the AD9959/PCBZ). In particular, is there a way to externally drive pins P0-P3 of the board in a way that has high input impedance? I am trying to toggle the DDS core between two frequencies using an external trigger signal, but when I connect to the pins on the "MANUAL I/O CONTROL HEADERS" on the board, the input impedance is quite low (and it seems that the trigger signal percolates into the DDS core, for example causing a modulation of the DC offset of the output signal). I tried removing the jumpers labeled "Remove jumpers for manual control" but this seemed to stop any control of pins P0-P3 (both external as well as using the software commands).