LM393, LM393A, LM293, LM2903, LM2903V
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 (VOL to VOH). To alleviate this
situation, input resistors < 10 kΩ 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 7. Zero Crossing Detector
(Single Supply)
+15 V
R4
220 k
6.8 k
R2
R5
220 k
Figure 8. Zero Crossing Detector
(Split Supply)
Vin(min)
Vin
R1
8.2 k
Vin
R1
D1
*
LM393
)
10 M
10 k
+VCC
Θ
10 k
VCC
VO
– VEE
∆Θ
Θ
15 k
R3
Vin
*
LM393
)
–VEE
D1 prevents input from going negative by more than 0.6 V.
R1 + R2 = R3
R3
≤
R5
for small error in zero crossing.
10
Vin(min)
[
0.4 V peak for 1% phase distortion (∆Θ).
Figure 9. Free–Running Square–Wave Oscillator
1.0 MΩ
VCC
RL
10 k
VO
t
Figure 10. Time Delay Generator
VCC
R
–
LM393
VC
+
–
LM393
+
+ Vref
Vin
0
VO
0
VC
0
tO
Vref
VCC
RL
–
VCC
51 k
0.001
µF
LM393
+
C
VO
51 k
51 k
VCC
VO
0
t
‘‘ON’’ for t
where:
tO +
∆t
n(
Vref
)
VCC
∆t
= RC
Vref
t
Figure 11. Comparator with Hysteresis
VCC
RS = R1 | | R2
RS
–
LM393
+
Vref
R1
R2
RL
Vth1 = Vref +
(VCC –Vref) R1
R1 + R2 + RL
(Vref –VO Low) R1
R1 + R2
Vth2 = Vref –
MOTOROLA ANALOG IC DEVICE DATA
5
MOTOROLA [ MOTOROLA, INC ]
