Application Note
9 of 23
V 1.1
2020-11-09
CoolGaN™ 600 V half-bridge evaluation platform featuring GaN
EiceDRIVER™
Setup and use
4
Setup and use
Attention:
This evaluation board has exposed high-voltage contacts. Use appropriate protective
measures to avoid shock. The evaluation board has no overcurrent shutdown, so it is possible
to drive the GaN transistors to currents far beyond their rating, which may result in their
destruction. Use appropriate protective covers to prevent any possible injury from exploding
components. Observe the maximum rating of the DC bus capacitor, and keep the bus voltage
below 450 V. Exceeding this value risks the capacitor venting violently. Always set
appropriate current limit values on the external lab power supplies to minimize catastrophic
damage to the board in the event of a fault. It is up to you to set the PWM input signal
appropriately to avoid damage.
4.1
Test equipment needed
5 V power supply capable of 0.5 A output current to supply V
cc
.
Bus voltage supply up to 450 V DC with sufficient current to supply the power needed for the planned
testing. For short pulse testing even to maximum current, the current drawn from the bus voltage supply is
very small, as the DC bus bulk storage capacitor provides the instantaneous energy.
Signal generator to provide the necessary PWM drive command for the half-bridge. The generator must be
capable of driving standard 5 V logic levels into a 50 Ω terminated load. Rise and fall time should be in the 5
ns range for best timing accuracy/repeatability.
1.2 mm slotted screwdriver for adjusting the deadtime trimpots R11 and R21.
Interconnect cable for PWM input: The PWM input connector is a 50 Ω terminated MMCX coaxial connector.
Assuming the signal source is a conventional BNC connector, you will need a BNC male to MMCX plug cable
(
) or a BNC to MMCX adapter.
Oscilloscope for measurement. Due to the fast transient voltage and current possible using GaN transistors,
an oscilloscope with a bandwidth >500 MHz is recommended.
For measuring the high-side gate voltage, an isolated probe with a bandwidth of 500 MHz or better, such as
the
is recommended. An MMCX connector is provided for this purpose (TP1 on
the back side of the board). We are not aware of any other isolated probe with sufficient common-mode
transient immunity to accurately measure the high-side gate voltage.
A standard (>500 MHz) passive probe with the short ground pin can be used to measure Q2 low-side gate
voltage on TP2, but the test point reference on the Kelvin source of Q2 may have ground bounce compared
to the V
sw
measurement reference due to L di/dt ground bounce. A common-mode core on each passive
probe cable can help minimize any measurement artifacts due to common-mode cable shield currents.
Another effective solution is to use a 1 GHz active differential proble such as the
. This
can further minimize measurement errors/artifacts due to common-mode ground currents, but can be
sensitive to coupled dv/dt from the TIVM1 probe snout.
Make sure the voltage probe used on TP3 to measure the switch node voltage is rated appropriately for
voltage and bandwidth. We recommend a
high-voltage probe with 800 MHz bandwidth.
4.2
Connections to the terminal block
With the exception of the coaxial PWM connection to J1, all other I/O and power connections to the evaluation
board are made to the pluggable terminal-block X1. The pluggable terminal block makes it more convenient to
remove the board from the test-bench for any component value changes during test, without having to
disconnect and reconnect everything each time a change is made.