HCPL-3120 Datasheet, PDF (14/15 Pages) Agilent(Hewlett-Packard) – 2.0 Amp Output Current IGBT Gate Drive Optocoupler

1
8
C_LEDP
2
7
3
6
C_LEDN
4
5
Figure 29. Optocoupler Input to Output
Capacitance Model for Unshielded Optocouplers.
1
C_LEDO1
8
C_LEDP
2
7
C_LEDO2
3
6
C_LEDN
4
5
SHIELD
Figure 30. Optocoupler Input to Output
Capacitance Model for Shielded Optocouplers.
+5 V
+
V_SAT
–
1
C_LEDP
2
I_LEDP
3
C_LEDN
4
SHIELD
8
0.1
7
µF
+
–
V_CC = 18 V
6
•••
Rg
5
•••
* THE ARROWS INDICATE THE DIRECTION
OF CURRENT FLOW DURING –dV_CM/dt.
+–
V_CM
Figure 31. Equivalent Circuit for Figure 25 During
Common Mode Transient.
1
8
+5 V
C_LEDP
2
7
3
6
Q1
C_LEDN
I_LEDN
4
5
SHIELD
Figure 32. Not Recommended Open
Collector Drive Circuit.
1
8
+5 V
C_LEDP
2
7
3
6
C_LEDN
4
5
SHIELD
Figure 33. Recommended LED Drive
Circuit for Ultra-High CMR.
To minimize dead time in a given
design, the turn on of LED2
should be delayed (relative to the
turn off of LED1) so that under
worst-case conditions, transistor
Q1 has just turned off when
transistor Q2 turns on, as shown
in Figure 34. The amount of delay
necessary to achieve this condi-
tions is equal to the maximum
value of the propagation delay
difference specification, PDD_MAX,
which is specified to be 350 ns
over the operating temperature
range of -40°C to 100°C.
Delaying the LED signal by the
maximum propagation delay
difference ensures that the
minimum dead time is zero, but it
does not tell a designer what the
maximum dead time will be. The
maximum dead time is equivalent
to the difference between the
1-195