acpl-w302 Avago Technologies, acpl-w302 Datasheet - Page 12

• Manufacturer Part Number: acpl-w302
• Description: 0.4 Amp Output Current Igbt Gate Driver Optocoupler
• Manufacturer: Avago Technologies

Dead Time and Propagation Delay Specifications
The ACPL-W302 includes a Propagation Delay
Difference (PDD) specification intended to help
designers minimize “dead time” in their power inverter
designs. Dead time is the time high and low side power
transistors are off. Any overlap in Ql and Q2 conduction
will result in large currents flowing through the power
devices from the high voltage 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 24. The amount of delay necessary to
achieve this condition is equal to the maximum value
of the propagation delay difference specification, PDD
max, which is specified to be 500 ns over the operating
temperature range of -40° to 100°C.
Figure 24. Minimum LED Skew for Zero Dead Time.
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Data subject to change. Copyright © 2006 Avago Technologies Pte. All rights reserved.
AV01-0279EN - July 24, 2006
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 propagation delay difference
specification as shown in Figure 25. The maximum
dead time for the ACPL-W302 is 1 µs (= 0.5 µs - (-0.5
µs)) over the operating temperature range of –40°C to
100°C.
Figure 25. Waveforms for Dead Time.
Note that the propagation delays used to calculate PDD
and dead time are taken at equal temperatures and
test conditions since the optocouplers under
consideration are typically mounted in close proximity
to each other and are switching identical IGBTs.
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