LM393 Datasheet, PDF (5/10 Pages) Motorola, Inc – SINGLE SUPPLY, LOW POWER DUAL COMPARATORS

LM393, LM293, LM2903, LM2903V, NCV2903
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 kW 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.
+15 V
R1
R4
R5
8.2 k
220 k 220 k
10 k
V_{in R1}
6.8 k
*
LM393
D1 R2
)
15 k
10 M
R3
D1 prevents input from going negative by more than 0.6 V.
R1 + R2 = R3
R3 ≤
R5
10
for small error in zero crossing.
Figure 8. Zero Crossing Detector
(Single Supply)
V_in
V_in(min)
+V_CC
Q
*
10 k
V_in
LM393
)
V_CC
−V_EE
V_O
− V_EE
Q
DQ
V_in(min) [ 0.4 V peak for 1% phase distortion (DQ).
Figure 9. Zero Crossing Detector
(Split Supply)
1.0 MW
V_CC
51 k
−
0.001 mF _LM393
+
V_CC
R_L
10 k
V_O
51 k
V_CC
51 k
V_O
0
t
Figure 10. Free−Running Square−Wave Oscillator
V_CC
V_CC
t
R
R_L
−
−
LM393
LM393
+
V_C C
+
V_O
+ V_ref
‘‘ON’’ for t ­ t_O + Dt
where:
V_in V_ref
Dt
=
RC ȏ n (
V_ref
V_CC
)
0
V_O
0
V_C V_ref
0
t_O
ȏ
t
Figure 11. Time Delay Generator
R_S
R1
V_ref
−
LM393
+
R2
V_CC
R_L
R_S = R1 | | R2
V_th1 = V_ref +
(V_CC −V_ref) R1
R1 + R2 + R_L
(V_ref −V_O Low) R1
V_th2 = V_ref −
R1 + R2
Figure 12. Comparator with Hysteresis
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