System Considerations
Propagation Delay Difference (PDD)
The ACPL-516x 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 62) are off.
Any overlap in Q1 and Q2 conduction will result in large
Delaying the ACPL-516x turn-on signals 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 specifications
currents flowing through the power devices between as shown in Figure 79. The maximum dead time for the
the high and low voltage motor rails, a potentially cata-
strophic condition that must be prevented.
ACPL-516x is 800ns (= 400ns - (-400ns)) over an operat-
ing temperature range of -55 °C to 125 °C.
To minimize dead time in a given design, the turn-on of Note that the propagation delays used to calculate PDD
the ACPL-516x driving Q2 should be delayed (relative to
the turn-off of the ACPL-516x driving Q1) so that under
worst-case conditions, transistor Q1 has just turned off
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
when transistor Q2 turns on, as shown in Figure 78. The and are switching identical IGBTs.
amount of delay necessary to achieve this condition is
V
IN+1
OUT1
equal to the maximum value of the propagation delay
difference specification, PDD , which is specified to
be 400ns over the operating temperature range of -55
°C to 125 °C.
MAX
V
Q1 ON
Q1 OFF
Q2 ON
Q2 OFF
V
V
OUT2
V
V
IN+1
IN+2
t
PHL
t
MIN
OUT1
Q1 ON
PHL
MAX
Q1 OFF
Q2 ON
t
PLH
MIN
t
PLH
MAX
Q2 OFF
(t
t
)
= PDD*
MAX
PHL- PLH
V
V
MAX
OUT2
IN+2
MAXIMUM DEAD TIME
(DUE TO OPTOCOUPLER)
t
PHL
MAX
= (t
= (t
= PDD*
- t
- t
– PDD*
) + (t
- t
PLH PLH
MAX MIN
MIN
)
)
t
PHL
PHL
MAX
PHL
PLH
PLH
MAX
MAX
MIN
MIN
MIN
) – (t
- t
PHL
PLH
MAX
PDD* MAX = (t
- t
PHL PLH
)
= t
- t
PLH
PHL
MAX
MAX
MIN
MIN
*PDD = PROPAGATION DELAY
NOTE: FOR PDD CALCULATIONS THE PROPAGATION DELAYS
ARE TAKEN AT THE SAME TEMPERATURE AND TEST CONDITIONS.
*PDD = PROPAGATION DELAY DIFFERENCE
NOTE: FOR DEAD TIME AND PDD CALCULATIONS ALL PROPAGATION
DELAYS ARE TAKEN AT THE SAME TEMPERATURE AND TEST CONDITIONS.
Figure 78. Minimum LED Skew for Zero Dead Time.
Figure 79. Waveforms for Dead Time Calculation.
For product information and a complete list of distributors, please go to our website: www.avagotech.com
Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies in the United States and other countries.
Data subject to change. Copyright © 2005-2013 Avago Technologies. All rights reserved.
AV02-3964EN - May 1, 2013
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