19
FN7177.2
March 31, 2011
Free Running Oscillator Application
Figure
54 is an EL5144 configured as a free running
oscillator. To first order, ROSC and COSC determine the
frequency of oscillation according to:
For rail to rail output swings, maximum frequency of
oscillation is around 15MHz. If reduced output swings are
acceptable, 25MHz can be achieved. Figure
55 shows the
oscillator for ROSC = 510Ω, COSC = 240pF and
FOSC =6MHz.
FIGURE 52.
FIGURE 53.
FIGURE 54.
FIGURE 55.
FIGURE 56.
1
2
3
4
14
13
12
11
5
6
7
10
9
8
-
+
-
+
Sele
+5V
VOUT
150Ω
VIN 1
3VPP
0.1
4.7
VIN 2
2.4VPP
EL5246
0V
5V
VOUT
Selec
0V
5V
1
2
3
5
4
-
+
+5V
470K
0.1
470K
ROS
COS
5V
VOUT
0V
5V
FOSC
0.72
ROSC COSC
×
---------------------------------------
=
(EQ. 4)
EL5144, EL5146, EL5244, EL5246, EL5444