acpl-w314 Avago Technologies, acpl-w314 Datasheet - Page 13

• Manufacturer Part Number: acpl-w314
• Description: 0.4 Amp Output Current Igbt Gate Driver Optocouplers
• Manufacturer: Avago Technologies

Dead Time and Propagation Delay Specifications
The ACPL-P302/W302 includes a Propagation Delay Dif-
ference (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 de-
layed (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 speci-
fication, 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.
Delaying the LED signal by the maximum propagation de-
lay 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 specification as shown in Figure 25.
The maximum dead time for the ACPL-P302/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.