icl8038 Intersil Corporation, icl8038 Datasheet - Page 4

• Manufacturer Part Number: icl8038
• Description: Precision Waveform Generator/voltage Controlled Oscillator
• Manufacturer: Intersil Corporation

Test Circuit
Detailed Schematic
Application Information
An external capacitor C is charged and discharged by two
current sources. Current source #2 is switched on and off by a
flip-flop, while current source #1 is on continuously. Assuming
that the flip-flop is in a state such that current source #2 is off,
and the capacitor is charged with a current I, the voltage
across the capacitor rises linearly with time. When this voltage
reaches the level of comparator #1 (set at 2/3 of the supply
voltage), the flip-flop is triggered, changes states, and
releases current source #2. This current source normally
carries a current 2I, thus the capacitor is discharged with a
7
R
30K
Q
Q
Q
Q
Q
3
23
31
32
33
34
9
R
11K
R
39K
1
2
Q
Q
8
Q
30
24
6
Q
R
270
R
2.7K
7
11
12
Q
Q
Q
1
R
40K
25
2
46
Q
Q
CURRENT SOURCES
11
26
Q
Q
5
R
100
4
8
R
R
620
4
EXT
13
FLIP-FLOP
Q
R
27K
R
470
12
Q
B
14
15
1.8K
29
4
R
R
100
Q
16
5
3
Q
Q
Q
Q
Q
(See Functional Diagram)
4
R
100
13
27
R
5
9
10
6
Q
EXT
28
SW
N.C.
10
A
C
1
EXT
Q
R
4.7K
14
7
8
18
R
4.7K
10
4
17
Q
R
10K
C
3300pF
35
A
R
27K
Q
R
15K
FIGURE 1. TEST CIRCUIT
41
7B
19
Q
ICL8038
Q
COMPARATOR
R
4K
15
Q
R
27K
36
41
11
42
20
5
Q
Q
Q
ICL8038
Q
16
R
10K
38
37
21
BUFFER AMPLIFIER
B
Q
17
R
27K
R
10K
Q
43
11
Q
7A
22
Q
18
40
R
12
6
R
5K
5K
R
5K
Q
10
8
9
39
net-current I and the voltage across it drops linearly with time.
When it has reached the level of comparator #2 (set at 1/3 of
the supply voltage), the flip-flop is triggered into its original
state and the cycle starts again.
Four waveforms are readily obtainable from this basic
generator circuit. With the current sources set at I and 2I
respectively, the charge and discharge times are equal. Thus
a triangle waveform is created across the capacitor and the
flip-flop produces a square wave. Both waveforms are fed to
buffer stages and are available at pins 3 and 9.
82K
3
9
3
2
R
1K
44
2
2.7K
10K
2.7K
10K
R
800
R
R
R
R
R
800
19
20
21
Q
22
23
24
Q
R
10K
R
R
41
49
L
TRI
SINE
Q
Q
42
50
-10V
+10V
R
33K
R
33K
Q
Q
28
25
51
SINE CONVERTER
43
Q
Q
44
52
R
33K
R
33K
Q
Q
26
29
45
53
Q
Q
46
54
R
33K
R
33K
Q
Q
30
27
55
47
Q
Q
48
56
R
33K
R
33K
45
31
R
5.6K
R
200
R
375
R
330
R
1600
R
330
R
375
R
200
R
5.2K
40
33
34
35
36
37
38
39
32
6
12
1
V+
R
82K
EXT
C