An isolation circuitry and method are provided for
coupling between a power supply and
processing circuitry in order to provide power to the
processing circuitry whilst hiding a
power consumption characteristic of that
processing circuitry. The isolation circuitry comprises a plurality of sub-circuits, with each sub-circuit comprising a
capacitor, a first switch configured to provide a first connection between the
capacitor and the power supply, a second switch configured to provide a second connection between the
capacitor and the processing circuitry, and a third switch configured to provide a third connection across the capacitor to partially
discharge the capacitor. Control circuitry controls the plurality of sub-circuits, such that within each sub-circuit the first switch, second switch and third switch are placed in an
active state in a repeating sequence. Each of the plurality of sub-circuits further comprises a
comparator configured to place the third switch in an open state when a predetermined non-
zero voltage difference across the capacitor is reached during the
active state of the third switch. By such an approach, it is ensured that the
voltage across the
comparator at the end of the
discharge operation is always the same irrespective of the
voltage present at the start of the
discharge operation. As a result, the
power consumption characteristic of the processing circuitry is entirely hidden by the isolation circuitry. Further, the isolation circuitry of the present invention provides a particular
power efficient mechanism for hiding the
power consumption characteristic of the processing circuitry.