ADF41020 power sequencing (18 GHz PLL)

Using multiple (12 pcs) of ADF41020 to lock ~10 GHz oscillators in a test rig, working fine until recently - when all 12 failed. Now, wondering about the reason. As it turns out, Vp (charge pump supply voltage) was absent - a voltage pre-regulator failed that provides the supply for the Vp voltages (3.1 V). Analog and digital supply were OK.

Question - is there any particular need for power sequencing/can the ADF41020 handle situations with both digital and analog supplies (3.1 V) applied, but Vp switched off? If this is the issue, then all is clear, and the root cause for the failure identified. Any experience with such issues? For how long can Vp be switch off, before the ADF41020 will suffer, if at all?