Testing target resistances in circuit assemblies

摘要

A test system includes a circuit assembly having an IC and an external circuit. The IC includes test circuitry used to observe data indicative of target resistances in the external circuit. The test system evaluates the data to determine target resistance values. A first embodiment measures two output voltages responsive to a time varying reference voltage. The two output voltages can be used to determine resistance values in the external circuit. A second embodiment enables logic contention on the IC, controllably fixes a pull-down element on the IC, and controllably sweeps a pull-up element on the IC until the voltage at a node between the pull-down and pull-up elements and coupled to an external circuit exceeds a reference voltage.