80960KA EMBEDDED 32-BIT MICROPROCESSOR - Datasheet ...

80960KA2.5. Test Load CircuitFigure 12 illustrates the load circuit used to test the80960KA’s three-state pins; Figure 13 shows the loadcircuit used to test the open drain outputs. The opendrain test uses an active load circuit in the form of amatched diode bridge. Since the open-drain outputssink current, only the I OL legs of the bridge arenecessary and the I OH legs are not used. When the80960KA driver under test is turned off, the output pinis pulled up to V REF (i.e., V OH ). Diode D 1 is turned offand the I OL current source flows through diode D 2 .THREE-STATE OUTPUTC LC L = 50 pF for all signalsFigure 12. Test Load Circuit for Three-State Output PinsWhen the 80960KA open-drain driver under test ison, diode D 1 is also on and the voltage on the pinbeing tested drops to V OL . Diode D 2 turns off and I OLflows through diode D 1 .OPEN-DRAIN OUTPUTD 1C LC L = 50 pF for all signalsI OLD 2I OL Tested at 25 mAV REF = V CCD1 and D 2 are matchedFigure 13. Test Load Circuit for Open-Drain Output Pins14