LM393, LM393E, LM293, LM2903, LM2903E, LM2903V, NCV2903
www.onsemi.com
5
APPLICATIONS INFORMATION
These dual comparators feature high gain, wide
bandwidth characteristics. This gives the device oscillation
tendencies if the outputs are capacitively coupled to the
inputs via stray capacitance. This oscillation manifests
itself during output transitions (V
OL
to V
OH
). To alleviate
this situation, input resistors <10 k should be used.
The addition of positive feedback (<10 mV) is also
recommended. It is good design practice to ground all
unused pins.
Differential input voltages may be larger than supply
voltage without damaging the comparator’s inputs. Voltages
more negative than −0.3 V should not be used.
Figure 8. Zero Crossing Detector
(Single Supply)
Figure 9. Zero Crossing Detector
(Split Supply)
Figure 10. Free−Running Square−Wave Oscillator
Figure 11. Time Delay Generator
Figure 12. Comparator with Hysteresis
10
D1 prevents input from going negative by more than 0.6 V.
R1 + R2 = R3
R3 ≤
R5
for small error in zero crossing.
V
in
10 k
D1
R1
8.2 k
6.8 k
R2
15 k
R3
+15 V
10 m
R5
220 k
R4
220 k
LM393
V
in(min)
[ 0.4 V peak for 1% phase distortion ().
*
+V
CC
10 k
V
in
-V
EE
V
in
V
in(min)
V
CC
V
O
- V
EE
LM393
-
+
LM393
51 k
51 k
51 k
R
L
10 k
V
CC
V
CC
V
CC
V
O
V
O
t
0
1.0 m
0.001 F
-
+
LM393
V
CC
V
CC
V
O
V
in
V
O
+ V
ref
V
ref
V
ref
0
0
0
V
C
t
O
t
``ON'' for t t
O
+ t
where:
t = RC
ȏ n (
V
ref
V
CC
)
R
R
L
V
C
C
LM393
-
+
R
S
V
CC
R
L
V
ref
R1
R2
R
S
= R1 | | R2
V
th1
= V
ref
+
(V
CC
-V
ref
) R1
R1 + R2 + R
L
V
th2
= V
ref
-
(V
ref
-V
O
Low) R1
R1 + R2
R1
tȏ
+
-
LM393
)
*
)
