80960MC Datasheet, PDF (20/39 Pages) Intel Corporation – EMBEDDED 32-BIT MICROPROCESSOR WITH INTEGRATED FLOATING-POINT UNIT AND MEMORY MANAGEMENT UNIT

80960MC
2.5 Test Load Circuit
Figure 12 illustrates the load circuit used to test the
80960MC’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 80960MC 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 80960MC 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 11. 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 12. Test Load Circuit for Open-Drain
Output Pins
16
PRELIMINARY