EL5485C, EL5486C - Preliminary
Quad 4ns High Speed Comparators
output changes state. The non-inverting and inverting
inputs may be reversed.
back 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 VCC, but it is affected by
the tolerances of the resistors. The duty cycle can be
adjusted by changing VCC value.
V
+
-
IN
V
OUT
V
REF
1MHz to
5V
8MHz
200W
Crystal Oscillator
R
R
5kW
1
A simple crystal oscillator using one comparator of an
EL5485C and EL5486C is shown below. The resistors
R1 and R2 set the bias point at the comparator's non-
inverting input. Resistors R3, R4, and C1 set the invert-
ing input node at an appropriate DC average voltage
based on the output. The crystal's path provides resonant
positive feedback and stable oscillation occurs.
Although the EL5485C and EL5486C will give the cor-
rect 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 200W resistor attenuates the feed-
+
-
V
OUT
1.5kW
2
R
3
C
R
4
1
2kW
0.01µF
2kW
11
ELANTEC [ ELANTEC SEMICONDUCTOR ]
