el5181 Intersil Corporation, el5181 Datasheet - Page 9

• Manufacturer Part Number: el5181
• Description: 8ns High-speed Comparator
• Manufacturer: Intersil Corporation

Check the current through R
greater than the input bias current as follows:
The above two methods will generate hysteresis of up to a
few hundred millivolts. Beyond that, the impedance of R
low enough to affect the bias string and adjustment of R
may be required.
Power Dissipation
When switching at high speeds, the comparator's drive capa-
bility 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:
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notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
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SD
V
I
V
I
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
is the maximum ambient temperature
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
P
T
JMAX
DISS
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
I
=
For information regarding Intersil Corporation and its products, see www.intersil.com
=
=
T
0.5V
-------------------------------------- -
V
MAX
S
3
SD
9
I
and make sure that it is much
R
S
+
3
-V
+
V
JA
REF
SD
P
DISS
I
SD
S
SD
+ to V
JMAX
to ground
S
(125°C).
-
3
is
1
EL5181
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
changes state. The non-inverting and inverting inputs may
be reversed.
Crystal Oscillator
A simple crystal oscillator using one comparator of an
EL5181 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 EL5181 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
attenuates the feedback to the non-inverting input. The cir-
cuit 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
erances of the resistors. The duty cycle can be adjusted by
changing V
3
, R
4
1.5k
, and C
5k
R
R
1
2
5V
CC
0.01µF
1
C
value.
REF
set the inverting input node at an appropriate
1
V
REF
V
IN
threshold, the comparator's output
+
-
200
2k
R
4
CC
+
-
, but it is affected by the tol-
1MHz to 8MHz
2k
R
3
V
1
OUT
and R
V
2
OUT
resistor
set the