Analog circuit designer needs to sample a "ready" signal (1), in the digital section.

The passgate (2) may be turned off. So, a keeper (3) is placed on an inverter input (4).

The circuit can pass simulation, and could even function in silicon.

However, the digital section can be turned off. When the digital section is off, there is leakage in the parasitic body diode of the keeper.

Insight Analyzer reports this as a case of “Domain Leakage”.

A power switch block has been designed in schematic.

In the upper schematic, connections were swapped. Both the lower level, and the upper level, looked OK.

There is constant leakage to the “off” supply.

Insight Analyzer reports multiple violations

This level shifter passed through simulation. The output value was apparently functioning.

However, there will be internal leakage within this cell. Simulation did not catch this condition.

The level shifter uses inverters as the pull-down legs. The inverters will leak from cross-coupling to the low volt supply.

The inverters will leak from cross-coupling to the low volt supply.

Insight Analyzer reports this in multiple ways:

A voltage regulator can be turned off by passgate on supply rail.

A backup supply path is provided, from an alternate source, through a metal option link.

There is an either / or mode: The regulator can be active, or the alternate source can power its loads.

A failure exists when:

• Main supply is completely off.
• Backup supply is chosen.

The backup supply is powering into the dead main supply.

A test multiplexer opens up numerous possible cross- domain leakage paths.

Normal operation will usually guarantee one-hot selection within the multiplexers, ensuring DC paths are not created between sample points.

However, test multiplexers are often distributed, with scattered decode logic: Risky!

Insight Analyzer understands decoders, and finds the “needle in haystack” DC sneak paths. Proper decoding is ruled out.