Edge749
TEST AND MEASUREMENT PRODUCTS
Circuit Description
Driver Description
VHIGH
VLOW
V
HIGH
and V
LOW
V
HIGH
and V
LOW
define the logical “1” and “0” levels of
the DUT driver and can be adjusted anywhere over the
range determined by VCC and VEE. Table 1 documents
the relationship between the analog power to supplies
(VCC and VEE), the driver range (V
HIGH
and V
LOW
), and
the comparator threshold range (V
THRESHOLD
).
The V
HIGH
and V
LOW
inputs are unbuffered in that they
also provide the driver output current (see Figure 3), so
the source of V
HIGH
and V
LOW
must have ample current
drive capability.
VHIGH
DATA IN
DUT
DVR EN*
Figure 1. Driver Diagram
As shown in Figure 1, Edge749 supports programmable
high and low levels and tristate per channel. There are
no shared lines between any drivers. The DVR EN* and
DATA IN signals are TTL compatible inputs that control
the driver (see Figure 2).
With DVR EN* high, the DUT driver goes into a high
impedance state. With DVR EN* low, DATA IN high forces
the driver into a high state (DUT = V
HIGH
), and DATA IN
low forces the driver low (DUT = V
LOW
).
DVR EN*
DUT
VLOW
DATA IN
VHIGH
VLOW
DUT
Figure 3.
Simplified Model of the
Unbuffered Output Stage
Figure 2. Driver Functionality
Drive
Common Mode Range
VEE <= DUT <= VCC
Receive
Common Mode Range
VEE <= DUT <= VCC
Threshold
Range
VEE + 3V <= THRESHOLD <= VOC - 3V
Table 1. Headroom vs. Power Supplies
Revision 3 / October 21, 2002
4
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