12
500
VCC = 15 V
CL = 100 pF
RL = 20 kΩ
400 TA = 25°C
tPLH
tPHL
300
200
100
0
5
10
15
20
IF – FORWARD LED CURRENT – mA
Figure 12. Propagation Delay vs. Input
Current.
1
+5 V
2
310 Ω
3
CMOS
4
20 kΩ
8
0.1 µF
7
20 kΩ
+
–
VCC = 15 V
SHIELD
6
VOUT
100 pF
5
*100 pF TOTAL
CAPACITANCE
Figure 13. Recommended LED Drive Circuit.
1
CLEDP
2
8
20 kΩ
7
3
6
CLEDN
4
5
SHIELD
Figure 14. Optocoupler Input to
Output Capacitance Model for
Unshielded Optocouplers.
1
8
20 kΩ
2 CLEDPCLED02
7
CLED01
3
6
CLEDN
4
5
SHIELD
Figure 15. Optocoupler Input to
Output Capacitance Model for
Shielded Optocouplers.
1
+5 V
2
310 Ω
20 kΩ
8
0.1 µF
7
20 kΩ
+
–
VCC = 15 V
CMOS
3
4
SHIELD
6
VOUT
100 pF
5
*100 pF TOTAL
CAPACITANCE
Figure 16. LED Drive Circuit with Resistor Connected to LED Anode (Not
Recommended).