HCPL-315J Datasheet, PDF (19/21 Pages) Agilent(Hewlett-Packard) – 0.5 Amp Output Current IGBT Gate Drive Optocoupler

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high state (assuming LED is
“ON”) with a typical delay, UVLO
TURN On Delay, of 0.8 µs.
IPM Dead Time and
Propagation Delay
Specifications
The HCPL-3150/315J includes a
Propagation Delay Difference
(PDD) specification intended to
help designers minimize “dead
time” in their power inverter
designs. Dead time is the time
period during which both the
high and low side power
transistors (Q1 and Q2 in Figure
25) are off. Any overlap in Q1
and Q2 conduction will result in
large currents flowing through
the power devices from the high-
to the low-voltage motor rails.
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
maximum and minimum propaga-
tion delay difference specifica-
tions as shown in Figure 35. The
maximum dead time for the
HCPL-3150/315J is 700 ns
(= 350 ns - (-350 ns)) over an
operating temperature range of
-40°C to 100°C.
Note that the propagation delays
used to calculate PDD and dead
time are taken at equal tempera-
tures and test conditions since
the optocouplers under consider-
ation are typically mounted in
close proximity to each other and
are switching identical IGBTs.
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.