ADRF6518 constant DC after spike.

We’re designing a product with ADRF6518 which is used for AGC and filtering ahead AD9613 ADC. The signal source for ADRF6518 is ADL5380 quadrature demodulator.
When we change modes on the transmitter, sometimes ADRF6518 locks up, i.e. there’s only some DC offset instead of transmitted carrier (sometimes in one channel, sometimes in both). When changing modes on the transmitter we observe a short spike at the ADRF6518’s input near 4.6 V, after which output of ADRF6518 has only DC offset, VPK (peak voltage detector) output has only DC offset too. This behavior does not depend on ADRF6518 register state or VGN pins voltage. In datasheet we found


1) maximum input swing 5.0 V p-p
2) absolute maximum ratings for INP1, INM1, INP2, INM2 = VPS + 0.5 V . In our case VPS = 3.3 V VPI = 5 V.


Is our input signal valid?


Now we can restore functionality of ADRF6518 by a few different ways:
1)  turning off and on
2)  pull VICM/AC to GND, but it is not right way, because ADRF6518 common mode voltage is driven by ADL5380.
3)  reconfigure tx again, sometimes it can help.


On attached time diagrams you can see the input (blue curve) and output (green curve) of ADRF6518 at the moment of transmitter reconfiguration.