1
2
8
7
1
2
8
7
20
+5 V
kΩ
20 kΩ
C
20 kΩ
LEDP
C
LED02
C
LED01
310 Ω
V
OUT
C
LEDN
3
4
6
5
3
4
6
5
I
CLEDN*
Q1
100 pF
+ V ** –
R
SHIELD
SHIELD
* THE ARROWS INDICATE THE DIRECTION OF CURRENT
FLOW FOR +dV /dt TRANSIENTS.
CM
** OPTIONAL CLAMPING DIODE FOR IMPROVED CMH
PERFORMANCE.
V
< V
DURING +dV /dt.
R
F (OFF)
CM
Figure 25. Not Recommended Open
Collector LED Drive Circuit.
+
V
CM
Figure 24. AC Equivalent Circuit for Figure 19 During
Common Mode Transients.
1
2
8
7
20
kΩ
C
20 kΩ
LEDP
C
1
8
7
LED02
C
+5 V
LED01
20 kΩ
V
C
Q1
OUT
LEDN
2
3
3
4
6
5
I
CLEDN*
100 pF
6
5
SHIELD
4
* THE ARROWS INDICATE THE DIRECTION OF CURRENT
SHIELD
FLOW FOR +dV /dt TRANSIENTS.
CM
+
V
CM
Figure 27. Recommended LED Drive
Circuit for Ultra High CMR.
Figure 26. AC Equivalent Circuit for Figure 25 During
Common Mode Transients.
HCPL-4506
1
2
8
7
V
CC1
0.1 µF
20 kΩ
IPM
I
LED1
20 kΩ
+5 V
+HV
V
310 Ω
CMOS
OUT1
3
4
6
5
Q1
Q2
M
SHIELD
HCPL-4506
HCPL-4506
1
2
8
7
V
CC2
-HV
0.1 µF
20 kΩ
HCPL-4506
HCPL-4506
HCPL-4506
HCPL-4506
I
LED2
20 kΩ
+5 V
310 Ω
CMOS
V
OUT2
3
4
6
5
SHIELD
Figure 28. Typical Application Circuit.
1-60
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
