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EVM Tuning
6.1.3 Switch to Unipolar Bias Supply
The secondary side bipolar power supply can be switched to a unipolar power supply. The high side and low
side can be adjusted separately. To change the high-side gate driver to a unipolar power supply, short R10 and
remove R15; to change the low-side gate driver to a unipolar power supply, short R31 and remove R36.
Be aware that VDD-COM should be below 19 V when this board is used to drive Wolfspeed's SiC modules,
as 19 V is the absolute max Vgs for the module. If this method is used to change the bipolar supply to a
unipolar supply, either reduce the VIN to below 11.3 V or regulate the voltage by using the U4 and U5 LDO.
Otherwise, the gate-source voltage is likely to exceed the maximum operating value of the Wolfspeed SiC
MOSFET module.
6.1.4 Bypass VDD LDO
The VDD LDO can be bypassed on either the high side gate driver or the low side. To bypass the VDD LDO on
the high side gate driver, populate R1. To bypass the VDD LDO on the low side gate driver, populate R16.
6.2 Adjust Drive Strength
6.2.1 Without Booster
To adjust the drive strength, change the gate resistors, R47 and R51. The maximum drive strength for the
UCC217xx family can be calculated by the equation below:
I
= min 10A,
source_peak
R OH_EFF + R ON + R G_Int
V DD − V EE
I
= min 10A,
sink_peak
R OL + R OFF + R G_Int
R
and R
stand for the external gate resistors. R
ON
OFF
MOSFET. R
and R
OH_EFF
data sheet.
6.2.2 Enabling/Disabling Booster Stage
If a higher drive strength is required, an on-board booster stage can be populated. To populate the booster
stage, remove R47 and R51, populate Q1 with PHPT60410NYX, and populate Q2 with PHPT60410PYX for
the low-side gate driver. Remove R81 and R85, populate Q4 with PHPT60410NYX, and populate Q5 with
PHPT60410PYX for the high-side driver. Other BJTs with the same package can also be used.
The booster stage might impede the soft turn-off feature. To realize soft turn-off after enabling the booster stage,
a damper circuit, the R56/C46 combination for low-side driver and the R89/C61 combination for high-side driver,
can be used. Without the damper circuit, the OUTL pin will try to sink the soft turn-off current from the base
of the booster stage. The booster stage will amplify this current and result in a larger turn-off current for the
IGBT/SiC MOSFET and a higher Vds overshoot. The capacitor in the damper circuit can help mediate this issue
by supplying current to the OUTL pin during a soft turn-off event, thus resulting in lower current being pulled from
the base of the booster stage and lower turn-off current for the SiC MOSFET/IGBT.
6.3 Adaptations for Other ISO5x5x / UCC217xx Variants
6.3.1 Adapting EVM for UCC21732/39
Main Difference
UCC21732 and UCC21739 do not have
internal Miller clamp; an external Miller clamp
can be used.
20
UCC217xx and ISO5x5x Half-Bridge EVM User's Guide for Wolfspeed 1200-V
SiC Platforms
V DD − V EE
values can be obtained from the electrical characteristic section of the UCC217xx
OL
Pins/Parts Affected
•
Pin 7: CLMPE
•
R60 and R92
•
Q3 and Q6
Copyright © 2023 Texas Instruments Incorporated
stands for the internal gate resistor of the IGBT/SiC
G_Int
•
•
www.ti.com
Actions
Desolder R60 and R92
Populate Q3 and Q6 with Miller Clamp
FETs
SLUUCK0 – SEPTEMBER 2023
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