Edge749
TEST AND MEASUREMENT PRODUCTS
Application Information
(continued)
Also, either the pull up or pull down resistor could be
used to terminate the transmission from the DUT to the
pin electronics in an effort to minimize any reflections.
VHIGH A
VLOW A
Two Logic Family Driver
Many test systems support exactly two families of driver
and receiver levels and select between family A and family
B settings on a per-pin basis, typically using an analog
multiplexer (See Figure 11). Common examples of these
families are:
Family A = TTL
Family B = CMOS
or
Family A = TTL
Family B = ECL
The Edge749 supports this system architecture with
minimal hardware and the elimination of the per-pin
analog multiplexer. The drive and receive levels need to
be generated once per system, then distributed and
buffered suitably.
DATA IN A
DUT
DVR EN*A
VHIGH B
VPULL UP
DATA IN B
VPULL DOWN
VLOW B
DVR EN*B
Figure 9. Driver with Pull Up/Pull Down
Trinary Driver with Termination
Other combinations are also possible. For example, two
parallel drivers can be configured to implement one
trinary driver with a pull down (or pull up) dynamic
termination (see Figure 10).
VHIGH A
VLOW A
Parametric Functions
Two drivers in parallel also offer the possibility of
connecting force and sense parametric circuitry to the
DUT without adding additional circuitry to the controlled
impedance DUT line. For example, Figure 12 shows the
second driver being utilized to force a current and
measure a voltage.
Notice that the V
HIGH
and V
LOW
pins are used from
different drivers to allow the force and sense functions
to be active simultaneously.
DATA IN A
DVR EN*A
VHIGH B
VTERMINATION
DATA IN B
DUT
DVR EN*B
Figure 10. Trinary Driver with Termination
Revision 3 / October 21, 2002
8
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