el5281 Intersil Corporation, el5281 Datasheet - Page 9

• Manufacturer Part Number: el5281
• Description: Dual 8ns High-speed Comparator
• Manufacturer: Intersil Corporation

These two methods will generate hysteresis of up to a few
hundred millivolts. Beyond that, the impedance of R
enough to affect the bias string and adjustment of R
required.
Power Dissipation
When switching at high speeds, the comparator's drive
capability is limited by the rise in junction temperature
caused by the internal power dissipation. For reliable
operation, the junction temperature must be kept below
T
An approximate equation for the device power dissipation is
as follows. Assume the power dissipation in the load is very
small:
where:
I
Please refer to the performance curve to choose the input
driving frequency. Having obtained the power dissipation,
the maximum junction temperature can be determined as
follows:
where:
Threshold Detector
The inverting input is connected to a reference voltage and
the non-inverting input is connected to the input. As the input
passes the V
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SD
JMAX
V
I
V
I
N is the number of comparators in the package
T
T
S
SD
JA
MAX
S
SD
strongly depends on the input switching frequency.
is the analog quiescent supply current per comparator
is the analog supply voltage from V
is the digital supply current per comparator
is the thermal resistance of the package
is the digital supply voltage from V
(125°C).
is the maximum ambient temperature
REF
P
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
DISS
T
JMAX
threshold, the comparator's output
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
=
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=
V
S
T
MAX
u
I
S
9
+
+
V
4
SD
JA
u
u
I
P
SD
DISS
S
SD
+ to V
u
N
to ground
S
-
1
3
may be
is low
EL5281
changes state. The non-inverting and inverting inputs may
be reversed.
Crystal Oscillator
A simple crystal oscillator using one comparator of an
EL5281 is shown below. The resistors R
bias point at the comparator's non-inverting input. Resistors
R
DC average voltage based on the output. The crystal's path
provides resonant positive feedback and stable oscillation
occurs. Although the EL5281 will give the correct logic
output when an input is outside the common mode range,
additional delays may occur when it is so operated.
Therefore, the DC bias voltages at the inputs are set about
500mV below the center of the common mode range and the
200: resistor attenuates the feedback to the non-inverting
input. The circuit will operate with most AT-cut crystal from
1MHz to 8MHz over a 2V to 7V supply range. The output
duty cycle for this circuit is roughly 50% at 5V V
affected by the tolerances of the resistors. The duty cycle
can be adjusted by changing V
3
, R
4
, and C
1
R
R
set the inverting input node at an appropriate
1
2
0.01µF
5V
V
1.5k:
5k:
REF
C
V
1
IN
200:
+
-
2k:
R
+
-
4
CC
1MHz to
2k:
R
8MHz
value.
3
V
OUT
1
and R
V
OUT
CC
2
set the
, but it is