Deriving Boundary Scan Diagnostic Coverage for High Density ASIC Arrays
Deriving boundary scan coverage for high-density ASIC arrays requires precise accounting of scannable versus un-scannable nets to prevent costly field escapes.
Test Clock Jitter
Timing Uncertainty
Automated test equipment relies on ultra-stable periodic reference signals to sample high-speed digital waveforms and measure device timing characteristics accurately. Elevated test clock jitter introduces phase uncertainty into automated test systems, obscuring true device-under-test performance metrics and causing false test failures. Phase noise within clock generation hardware appears as cycle-to-cycle or period jitter during signal acquisition.
High-speed serial interfaces, such as PCIe and Ethernet transceivers, require extremely clean test clocks to prevent test margin degradation during physical layer compliance validation. Oscilloscopes and bit error rate testers require phase-locked loop clock sources with low intrinsic phase noise.
Measurement Degradation
Spurious phase fluctuations in automated test clock distribution networks consume device timing margins and artificially degrade measured eye openings. Excessive test clock jitter prevents accurate characterization of transmitter phase noise and receiver jitter tolerance limits. Test engineers utilize clean external clock synthesized sources to isolate device behavior from test fixture noise.
Clock filtering circuits reduce high-frequency phase noise components across measurement signal paths.
Calibration Limit
Equipment clock instability metrics describe test system instrumentation limits and do not represent phase noise generated within the device under test. Test clock jitter establishes the minimum baseline timing uncertainty for automated physical layer compliance measurements. Periodic instrument calibration verifies clock stability against traceable frequency standards.