Datasheet

9
0.80
0.85
0.90
0.95
1.00
1.05
-40 -20 0 20 40 60 80 100 120 140
T
A
- TEMPERATURE -°C
NORMALIZED OUTPUT CURRENT
I
F
= 10mA
V
O
= 0.6V
0
2
4
6
8
10
12
0 5 10 15 20
I
O
- OUTPUT CURRENT - mA
I
F
- FORWARD CURRENT - mA
25°C
125°C
-40°C
V
O
=0.6V
Figure 2. Typical Transfer Characteristics.
Figure 3. Normalized Output Current vs. Temperature.
IPM Dead Time and Propagation Delay Specications
The ACPL-M46U-000E includes a Propagation Delay Dif-
ference specication intended to help designers mini-
mize 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 22) are
o. Any overlap in Q1 and Q2 conduction will result in
large currents owing through the power devices be-
tween the high and low voltage motor rails.
To minimize dead time the designer must consider the
propagation delay characteristics of the optocoupler as
well as the characteristics of the IPM IGBT gate drive cir-
cuit. Considering only the delay characteristics of the op-
tocoupler (the characteristics of the IPM IGBT gate drive
circuit can be analyzed in the same way) it is important
to know the minimum and maximum turn-on (t
PHL
) and
turn-o (t
PLH
) propagation delay specications, prefer-
ably over the desired operating temperature range.
The limiting case of zero dead time occurs when the in-
put to Q1 turns o at the same time that the input to Q2
turns on. This case determines the minimum delay be-
tween LED1 turn-o and LED turn-on, which is related
to the worst case optocoupler propagation delay wave-
forms, as shown in Figure 23. A minimum dead time of
zero is achieved in Figure 23 when the signal to turn on
LED is delayed by (t
PLH max
- t
PHL min
) from the LED1 turn
o. Note that the propagation delays used to calculate
PDD are taken at equal temperatures since the optocou-
plers under consideration are typically mounted in close
proximity to each other. (Specically, t
PLH max
and t
PHL min
in the previous equation are not the same as the t
PLH max
and t
PHL min
, over the full operating temperature range,
specied in the data sheet.) This delay is the maximum
value for the propagation delay dierence specication
which is specied at 370 ns for the ACPL-M46U-000E over
an operating temperature range of -40°C to 125°C.
Delaying the LED signal by the maximum propagation
delay dierence 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 occurs in
the highly unlikely case where one optocoupler with
the fastest t
PLH
and another with the slowest t
PHL
are in
the same inverter leg. The maximum dead time in this
case becomes the sum of the spread in the t
PLH
and t
PHL
propagation delays as shown in Figure 24. The maximum
dead time is also equivalent to the dierence between
the maximum and minimum propagation delay dier-
ence specications. The maximum dead time (due to the
optocouplers) for the ACPL-M46U-000E is 520 ns (= 370
ns - (-150 ns)) over an operating temperature range of
-40°C to 125°C.