E649APJ(1996) Просмотр технического описания (PDF) - Semtech Corporation

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E649APJ
(Rev.:1996)

Octal Pin Electronics Driver/Receiver

Semtech Corporation 

EDGE HIGH-PERFORMANCE PRODUCTS

Application Information (continued)

Edge649

Window Comparator

Trinary Driver

Certain applications require a dual threshold window

comparator to distinguish between the DUT being high,

low, or floating. To support this application, two Edge649

channels can be combined to create one channel with a

window comparator (see Figure 7). Notice that

connecting two DUT pins ties together the positive inputs

of both receivers. The result is a difference in polarity

between the digital outputs reporting the high and low

status of the DUT.

At times, there is a need for a three-level driver. Typically,

two levels are required for the standard digital “1” and

“0” pattern generation. The third level provides a higher

voltage to place the device under test (DUT) into a

programming or test mode. By controlling the DATA IN

and DVR EN* inputs, a trinary driver with tristate is

realizable (see Figure 8).

Driver with Pull Up/Pull Down

–

DUT HIGH

+

+

DUT LOW*

–

High Threshold

DUT

Low Threshold

Figure 7. Edge649 as a

Window Comparator

Once two receivers are connected as window

comparators, the two drivers also get connected in

parallel. This dual driver configuration supports a

multitude of applications that have traditionally been

difficult to accommodate.

As the drivers are unbuffered, paralleling two drivers for

one DUT node provides a means for adding pull up or

pull down capability. By connecting the VHIGH and VLOW

inputs of one driver through a resistor to a voltage,

additional functionality that would normally require an

external relay on the DUT transmission line to engage

and disengage these functions is realizable.

One common application for the pull up feature is testing

open collector devices. The pull down satisfies open

emitter DUTs (typically ECL). Either the pull up or down

could be used to establish a default high impedance

voltage on a bidirectional bus. Notice that in all

applications, the resistors can be switched dynamically

or statically.

VHIGH A

VLOW A

DATA IN A

DVR EN*A

DATA IN B

DVR EN*B

 2000 Semtech Corp.

VHIGH B

DUT

VHIGH B

VHIGH A

VLOW A

Figure 8. Trinary Driver

7

www.semtech.com

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