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ADF5355 - I have multiple chips that fail because the VCO starts drawing current! What causes this? They will sometimes lock and then unlock after ~20 minutes when the VCO starts drawing current.

Question asked by SFW_PLL on Aug 17, 2017
Latest reply on Sep 5, 2017 by MRichardson

The ref divider output is clean (17MHz) and the N divider shows a slightly low frequency. The tuning voltage will usually be around 0.5 volts (when locked it is ~ 2.2 volts) and it draws ~ 0.5 ma. The charge pump is set for full current output but does not seem to be able to overcome the bias current.

There is a fan on the board and the chip top is ~ 35 C.