Gate Resistor Consideration - Broadcom Infineon EasyPIM ACPL-337J Reference Manual

ACPL-337J Reference Manual Infineon EasyPIM™ 1B IGBT Module EB600-337J Evaluation Board
When IGBT is switching off, a reverse current flows for a short time, which prevents the diode from achieving its blocking
capability until the charge in the junction is depleted. During this time, the positive voltage slope between the collector and
the emitter results in current that tends to charge the blanking capacitor. The minimization of this current and the avoidance
of false DESAT triggering are achieved with fast diodes. Aside from DESAT and Zener diodes in series, there is one more
component that ensures the safety of the driver—a 1-kΩ resistor (R1 in Figure 10) in series with the previous components.
This resistor limits the current caused by negative voltage spikes (generated by inductive loads or reverse recovery spikes
of the free-wheeling diode) on the DESAT pin, thus preventing damage to the driver. To additionally prevent false fault signals
caused by negative voltage spikes on the DESAT pin, connect the Zener and Schottky diode between the DESAT and the
V pin.
E

4.2.4 Gate Resistor Consideration

The first step in choosing the appropriate gate resistor is to calculate its minimal value from the I specification. The
O(PEAK)
IGBT and the gate resistor can be analyzed as a simple RC circuit with a voltage supplied by the ACPL-337J.
Note that R can be different for high-side and low-side power switches. Therefore, calculations for both are necessary.
DS(MIN)
This external gate resistor combined with an internal minimal turn-on resistance ensures that the output current does not
exceed the device absolute maximum rating of 4A.
The next step in choosing the correct gate resistor is to check the power dissipation of the ACPL-337J gate driver. If the
power dissipation is too high, the resistance of the gate resistor should be increased. For detailed instructions on choosing
the gate resistor, refer to the ACPL-337J data sheet.
The final step in the turn-off gate resistor selection is ensuring that during turn-off, the transient at the maximal allowed
collector current, IGBT collector-emitter voltage does not exceed the blocking voltage on the IGBT device. The criteria for
the turn-on gate resistor are the maximal collector current peak, related to the reverse recovery of the opposite freewheeling
diode. This peak must not exceed double the value of the nominal collector current.
To ensure the constraints described previously, the EB600-337J comes with a 15Ω gate resistor as a default assembled
variant. In addition, the evaluation board is designed to enable Broadcom customers to evaluate switching characteristics of
the semiconductors by changing or combining turn-on/turn-off resistors (as described in Section 4.2.2, Gate Driver Circuit:
High-Voltage Side). Figure 12 shows the disposition of the gate resistors.
Figure 12: Disposition of the Gate Resistors
Broadcom ACPL-337J-EB600-RM100
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