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