4

 2004 Semtech Corp. / Rev. 5, 8/18/04

www .semtech.com

TEST AND MEASUREMENT PRODUCTS

Edge818

Circuit Description

Driver Description

The Edge818 supports programmable high and low levels

and tristate per channel.

There are no shared lines

between any drivers. The EN* and DATA signals are wide

voltage high impedance analog inputs capable of receiving

digital signals over a wide common mode range. VBB is

the high impedance analog input which sets the threshold

for EN* and DATA.

EN*, DATA

Status

> VBB

"1"

< VBB

"0"

With EN* high, the driver goes into a high impedance state.

With EN* low, DATA high forces the driver into a high state,

and DATA low forces the driver into a low state.

EN*

DATA

DOUT

1X

HiZ

01

VH

00

VL

Drive High and Low

VH and VL define the logical "1" and "0" levels of the driver,

and can be adjusted anywhere over the range determined

by VCC and VEE.

There are no restrictions between VH

and VL, other than they must remain within the power

supply levels.

VEE

≤ VH ≤ VCC

VEE

≤ VL ≤ VCC

The VH and VL inputs are unbuffered in that they also

provide the driver output current (see Figure 1), so the

source of VH and VL must have ample current drive

capability.

Figure 1. Simplified Model of the

Unbuffered Output Stage

Driver Output Protection

In a functional testing environment, where a resistor is

added in series with the driver output to create a 50

Ω

driver, the Edge818 can withstand a short to any legal

voltage for an indefinite amount of time.

In a low impedance application, with no additional output

resistance, the system should be designed to check for a

short circuit prior to connecting the driver, and tristate the

driver if a short is detected.

Receiver Description

The Edge818 supports a window comparator with

independent threshold levels per channel. There are no

shared comparator lines between channels. CVA and CVB

are high impedance analog voltage inputs which define

the threshold voltages for comparators A and B.

If VINP is more positive than CVA or CVB, QA and QB will

be high. Otherwise, QA and QB will be low.

VINP

QA

VINP

>

CVA

COMP HIGH

VINP

<

CVA

COMP LOW

VINP

QB

VINP

>

CVB

COMP HIGH

VINP

<

CVB

COMP LOW

VH

VL

DUT