Broadcom ACPL-32JT User Manual - Page 3
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ACPL-32JT, ACPL-C87AT
The IGBT collector voltage is sensed by the ACPL-32JT gate
drivers through the Desat pin. When desaturation events are
detected, ACPL-32JT applies a soft shutdown to the IGBT gate
to prevent damage. A PNP buffer transistor is used to
customize the shutdown process. The shutdown strength is
controlled by Rssd and Cssd.
Desat Blanking
Figure 4 Desat Blanking
The total blanking time is calculated in terms of internal
blanking time tDESAT(BLANKING) (0.6 μs typ), external
capacitance CBLANK (330 pF), FAULT threshold voltage VDESAT
(7V typ), and DESAT charge current ICHG (0.9 mA typ) as
follows:
tBLANK = tDESAT(BLANKING) + (CBLANK × VDESAT/ICHG)
= 0.6 μs + (330 pF × 7V/0.9 mA)
~ 3.2 μs
Active Clamp
Figure 5 Active Clamp
A Transient Voltage Suppressor (TVS) rated at 510V is placed
between the Gate and Collector of the IGBT to provide active
clamp protection. Vce of the IGBT is clamped and protected by
the TVS.
DC/DC Converter
Figure 6 DC/DC Converter
Each ACPL-32JT Gate Driver integrates a DC/DC converter that
provides distributed power to the secondary side.
For DC12 = 8V to 18V, this circuit nominally supports a
secondary-side load of up to 60 mA (including Icc2 of
ACPL-32JT) at the regulated VCC2 voltage.
Figure 7 Compensation Network
The compensation network is referenced to a nominal
transformer of Lp = 60 μH, Ls = 260 μH.
Broadcom
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User Guide