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4
2000 Semtech Corp.
www.semtech.com
EDGE HIGH-PERFORMANCE PRODUCTS
Circuit Description
Edge818
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
> VBB
< VBB
Status
"1"
"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*
1
0
0
DATA
X
1
0
DOUT
HiZ
VH
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 3), so the
source of VH and VL must have ample current drive
capability.
Figure 3. 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
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
VINP > CVA
VINP < CVA
QA
COMP HIGH
COMP LOW
VINP
VINP > CVB
VINP < CVB
QB
COMP HIGH
COMP LOW
VH
VL
DUT