80960KA Datasheet, PDF (17/43 Pages) Intel Corporation – EMBEDDED 32-BIT MICROPROCESSOR

80960KA
2.5. Test Load Circuit
Figure 12 illustrates the load circuit used to test the
80960KA’s three-state pins; Figure 13 shows the load
circuit used to test the open drain outputs. The open
drain test uses an active load circuit in the form of a
matched diode bridge. Since the open-drain outputs
sink current, only the I_OL legs of the bridge are
necessary and the I_OH legs are not used. When the
80960KA driver under test is turned off, the output pin
is pulled up to V_REF (i.e., V_OH). Diode D₁ is turned off
and the I_OL current source flows through diode D₂.
When the 80960KA open-drain driver under test is
on, diode D₁ is also on and the voltage on the pin
being tested drops to V_OL. Diode D₂ turns off and I_OL
flows through diode D₁.
THREE-STATE OUTPUT
C_L
C_L = 50 pF for all signals
Figure 12. Test Load Circuit for Three-State Output Pins
OPEN-DRAIN OUTPUT
D₁
I_OL
D₂
C_L
C_L = 50 pF for all signals
I_OL Tested at 25 mA
V_REF = V_CC
D1 and D₂ are matched
Figure 13. Test Load Circuit for Open-Drain Output Pins
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