Designing an Interface Between a DAS MTIF and a SUT
DAS MTIF Instructions
11
0.005
W
1.6 nH
0.7 pF
0.005
W
10 pF
Length = 10 inches
LOSSY1
1.6 nH
1 pF
1.6 nH
1.6 nH
0.7 pF
0.005
W
0.005
W
Length = 60 inches
LOSSY2
3.1V
12.5 k
W
250
W
90 k
W
Figure 9: Equivalent circuit for the DAS MTIF
The Low-Profile Extender used with the DAS MTIF increases the load. The
additional load is equivalent to a 100
W resistor connected in series with
approximately three inches of 75
W coaxial cable to the probe tip.
Although the extender can increase the loading significantly, using the extender
might be necessary in situations where there is as little as half an inch of
clearance.
The extender is useful in a SUT where signal risetimes are greater than one or
two nanoseconds. Faster risetimes cause transmission line reflections on signals.
Figure 10 shows the equivalent circuit for the DAS MTIF with a Low-Profile
Extender.
