EL5281CS ELANTEC [Elantec Semiconductor], EL5281CS Datasheet - Page 10

• Manufacturer Part Number: EL5281CS
• Description: Dual 8ns High-Speed Comparator
• Manufacturer: ELANTEC [Elantec Semiconductor]

EL5281C
Dual 8ns High-Speed Comparator
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
output changes state. The non-inverting and inverting
inputs may be reversed.
Crystal Oscillator
A simple crystal oscillator using one comparator of an
EL5281C is shown below. The resistors R
the bias point at the comparator's non-inverting input.
Resistors R
an appropriate DC average voltage based on the output.
The crystal's path provides resonant positive feedback
and stable oscillation occurs. Although the EL5281C
will give the correct logic output when an input is out-
side 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
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
R
, R
1
2
5V
0.01µF
4
, and C
V
5k
1.5k
C
REF
V
1
IN
REF
1
+
200
-
2k
R
set the inverting input node at
+
-
4
threshold, the comparator's
CC
1MHz to
8MHz
2k
R
3
value.
V
OUT
V
OUT
1
CC
and R
, but it is
resistor
2
set
10