Broadcom ACPL-352J, Reference Manual

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Broadcom ACPL-352J-EB1200-RM100
17
ACPL-352J Reference Manual Infineon EconoPIM™ 3 IGBT Module EB1200-352J Evaluation Board
Figure 10: DESAT Circuitry at ACPL-352J High-Voltage Side
Fault detection implemented in the ACPL-352J monitors the collector-emitter voltage of the IGBT and triggers a fault soft
shutdown sequence (SS) if the collector-emitter voltage exceeds the predefined threshold. A soft turn-off gate discharge
device slowly reduces the IGBT short circuit current to prevent damaging voltage spikes. Before the dissipated energy can
reach destructive levels, the IGBT is turned off. During the off state of the IGBT, the fault detection circuitry is disabled to
prevent false 'fault' signals. The OC fault detection circuitry must remain disabled for a short time period following the turn-on
of the IGBT, to allow the collector voltage to fall below the OC threshold. This time period, called the OC blanking time, is
controlled by the internal OC charge current, the OC voltage threshold, and the external OC capacitor. The nominal blanking
time is calculated in terms of external capacitance, FAULT threshold voltage (V
OC
), and DESAT charge current (I
CHG
) in
addition to an internal OC blanking time (t
OC(BLANKING)
). Figure 11 shows a diagram describing the operation of the driver
during an OC fault condition.
Figure 11: Circuit Behaviors during an Overcurrent Condition. The diagram is the same as in the ACPL-352J data sheet.
The OC terminal monitors the voltage between the collector and the emitter (V
CE
) of the IGBT. When this voltage exceeds
9V, the output voltages (VOUTP and VOUTN) go to high impedance state and the SS pulls down the VGATE at a slow rate
adjustable using the resistor. When the gate voltage falls below V
EE
+ 2V, the Miller clamp turns on to clamp the IGBT gate
to V
EE
. After this event, the FAULT output goes low. When t
OC(MUTE)
expires, the LED input must be kept low for t
OC(RESET)
before the fault condition is cleared. Afterwards, the FAULT status returns to high. The output stage responds to the input
only after the input fault condition has been cleared.