Resolving Non Compliant Interconnect Escape Rates in Hybrid Boundary Scan in Circuit Testing
Resolving boundary scan escape rates requires weighting fault coverage by defect universe and enforcing active guarding on unprobed parallel nets.
Multiplexed Pin Drivers
Channel Allocation
Automated test equipment uses a switching matrix to share expensive electronic resources across a large number of physical probe points. Deploying multiplexed pin drivers reduces the total number of independent drive and sense circuits required to test a high-density printed circuit board. This architecture balances the cost of the tester against the complexity of the interface hardware.
Hardware Economy
Each driver channel connects to several test pins through a relay or a solid-state switch. When multiplexed pin drivers are active, the software selects which pin receives the stimulus while the others remain in a high-impedance state. The configuration limits the number of pins that can be stimulated simultaneously.
Signal Integrity
Test program development must account for the physical constraints of the switching network. Engineers ensure that multiplexed pin drivers are not required to provide signals to two pins on the same net at the same time, as this would create a resource conflict. The path through the multiplexer adds capacitance and inductance to the signal line, which can affect the maximum frequency of the test.
Careful calibration of the tester compensates for the delays introduced by the switching matrix. This method allows a lower-cost tester to handle boards with thousands of nets by cycling through the available connections in sequential bursts.