EL5285C Elantec Semiconductor, EL5285C Datasheet - Page 10

• Manufacturer Part Number: EL5285C
• Description: Dual and Window 4ns High-Speed Comparators
• Manufacturer: Elantec Semiconductor

EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
output changes state. The non-inverting and inverting
inputs may be reversed.
Crystal Oscillator
A simple crystal oscillator using one comparator of an
EL5285C 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 EL5285C
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 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
R
, R
1
2
5V
0.01µF
4
, and C
V
5k
1.5k
C
REF
V
1
IN
1
+
200
-
2k
R
set the inverting input node at
+
-
4
CC
1MHz to
8MHz
2k
R
3
value.
V
OUT
V
OUT
1
CC
and R
, but it is
2
set
10