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AD8592 in shutdown

 First amp in AD8592 is unity gain buffer whose output feeds -IN of second amp in open loop, i.e. used as a comparator. +IN of second amp is used as reference for comparator.The whole chip is duty cycled using shutdown pin. During shutdown mode, +IN of second amp (reference for the comparator) is pulled to +5V through 150K. The input signal to first amp is zero during shutdown. Chip power supply: +5V.

Noticed an intermittent glitch that causes the comparator to change state even when it should not. This occurs during the transition from active to shutdown mode. Putting a 1M resistance between +IN of comparator and ground seems to reduce the glitch.

Could you please explain the cause for this behavior?