OP490E データシートの表示（PDF） - Analog Devices
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OP490E Datasheet PDF : 16 Pages
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OP490
Micropower Voltage-Controlled Oscillator
An OP490 in combination with an inexpensive quad CMOS
switch comprise the precision VCO of Figure 5. This circuit
provides triangle and square wave outputs and draws only 75 mA
from a 5 V supply. A acts as an integrator; S1 switches the
charging current symmetrically to yield positive and negative
ramps. The integrator is bounded by B which acts as a Schmitt
trigger with a precise hysteresis of 1.67 V, set by resistors R5,
R6, and R7, and associated CMOS switches. The resulting
output of A is a triangle wave with upper and lower levels of
3.33 V and 1.67 V. The output of B is a square wave with almost
rail-to-rail swing. With the components shown, frequency of
operation is given by the equation:
( ) fOUT =VCONTROL Volts ¥ 10 Hz /V
but this is easily changed by varying C1. The circuit operates
well up to a few hundred hertz.
VCONTROL
R1
200k⍀
R2
200k⍀
R3
100k⍀
C1
75nF
+5V
+5V
2
3
R4
200k⍀
4
1
11
1/4
OP490E
A
TRIANGLE
OUT
R5
200k⍀
6
5
+5V
IN/OUT
1
S1
OUT/IN
2
+5V
VDD 14
CONT
13
R8
200k⍀
R6
200k⍀
OUT/IN
3
IN/OUT
4
CONT
S2
12
IN/OUT
11
CONT
5
CONT
6
7 VSS
OUT/IN
S3
10
OUT/IN
+5V
9
S4
IN/OUT
8
7
1/4
OP490E
B
R7
200k⍀
SQUARE
OUT
Figure 5. Micropower Voltage Controlled Oscillator
–10–
REV. C
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