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HCPL-4506-000E Datasheet, PDF (21/21 Pages) AVAGO TECHNOLOGIES LIMITED – Intelligent Power Module and Gate Drive Interface Optocouplers | |||
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IPM Dead Time and Propagation Delay Specifications
The HCPL-4506 series include a PropaÂgation Delay Differ-
ence specificaÂtion intended to help designers minimize
âdead timeâ 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 Figureâ 24) are off. Any
overlap in Q1 and Q2 conducÂtion will result in large cur-
rents flowÂing through the power devices between the
high and low voltage motor rails.
To minimize dead time the designer must consider the
propaÂgaÂtion delay characteristics of the optocoupler
as well as the characÂteristics of the IPM IGBT gate drive
circuit. Considering only the delay characteristics of the
optoÂcoupler (the characteristics of the IPM IGBT gate
drive circuit can be analyzed in the same way) it is impor-
tant to know the miniÂmum and maximum turn-on (tPHL)
and turn-off (tPLH) propagation delay specifications, pref-
erably over the desired operating temperature range.
The limiting case of zero dead time occurs when the in-
put to Q1 turns off at the same time that the input to
Q2 turns on. This case determines the minimum de-
lay between LED1 turn-off and LED2 turn-on, which
is related to the worst case optocoupler propagaÂtion
delay waveforms, as shown in Figure 25. A minimum
dead time of zero is achieved in Figure 25 when the
signal to turn on LED2 is delayed by (tPLH max - tPHL
min) from the LED1 turn off. Note that the propagation
delays used to calculate PDD are taken at equal tem-
peratures since the optoÂcouplers under consideration
are typically mounted in close proximity to each other.
(Specifically, tPLHâmax and tPHLâmin in the previous equa-
tion are not the same as the tPLHâmax and tPHLâmin, over the
full operating temperature range, specified in the data
sheet.) This delay is the maximum value for the propagaÂ
tion delay differÂence specification which is specified at
450âns for the HCPL-4506 series over an operating tem-
perature range of Ââ40°C to 100°C.
Delaying the LED signal by the maximum propagation
delay difÂference ensures that the miniÂmum dead time
is zero, but it does not tell a designer what the maxi-
mum dead time will be. The maximum dead time oc-
curs in the highly unlikely case where one optoÂcoupler
with the fastest tPLH and another with the slowest tPHL
are in the same inverter leg. The maximum dead
time in this case becomes the sum of the spread
in the tPLH and tPHL propagation delays as shown in Figure 26.
The maximum dead time is also equivalent to the differ-
ence between the maximum and miniÂmum propagation
delay difference specifications. The maximum dead time
(due to the optocoupÂlers) for the HCPL-4506 series is
600âns (= 450âns -â(-150âns) ) over an operating tempera-
ture range of â40°C to 100°C.
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Data subject to change. Copyright © 2005-2008 Avago Technologies Limited. All rights reserved. Obsoletes AV01-0551EN
AV02-1360EN - June 20, 2008
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