Figure35.Waveformsfordeadtime.
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 35. The maximum dead time for the HCPL-3180 is
180 ns (= 90 ns-(- 90 ns)) over the 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 temperatures and test
conditions since the optocouplers under consideration
are typically mounted in close proximity to each other
and are switching identical IGBTs.
t
PLH
MIN
MAXIMUM DEAD TIME
(DUE TO OPTOCOUPLER)
= (t
PHL MAX
-
t
PHL MIN
) + (t
PLH MAX
-
t
PLH MIN
)
= (t
PHL MAX
-
t
PLH MIN
) – (t
PHL MIN
-
t
PLH MAX
)
= PDD* MAX – PDD* MIN
V
OUT1
I
LED2
V
OUT2
I
LED1
Q1 ON
Q2 OFF
Q1 OFF
Q2 ON
t
PHL MIN
t
PHL MAX
t
PLH MAX
PDD* MAX
(t
PHL-
t
PLH
)
MAX
*PDD = PROPAGATION DELAY DIFFERENCE
NOTE: FOR DEAD TIME AND PDD CALCULATIONS, ALL PROPAGATION DELAYS
ARE TAKEN AT THE SAME TEMPERATURE AND TEST CONDITIONS.
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Data subject to change. Copyright © 2005-2009 Avago Technologies. All rights reserved.
AV02-0165EN - March 10, 2009
