AD9257 power increase when clock turned off


We observed a power anomaly with the AD9257 when accidentally switching off a 40 MHz input clock before programmatically powering down the chip.  The current usage jumped from ~300 mA to nearly 750 mA!  This happened with any clock speed.  However, if we power on the chip before turning on the clock, current usage is minimal.  It only jumps if the clock goes on, then off again.

We can of course work around it by making sure we power down the chip before switching clocks, but this behavior was suprising.

Is this expected, and is there a danger to the chip?