GS-EVB-HB-66508B-RN Technical Manual
_____________________________________________________________________________________________________________________
GS-EVB-HB-66508B-RN Rev. 210118 © 2021 GaN Systems Inc.
www.gansystems.com 7
Please refer to the Evaluation Board/Kit Important Notice on page 26
CAUTION:
Check the shunt position
E
before the first time use. To complete the circuit
position
E
needs to be either shorted or a current shunt must be inserted
before powering up.
Measurement with current shunt:
1.
When measuring VSW with current shunt, ensure all channel probe grounds and current shunt
BNC output case are all referenced to the source end of Q2 before the current shunt. The
recommended setup of probes is shown as below.
2.
The output of coaxial current shunt can be connected to oscilloscope via 50
Ω
termination
impedance to reduce the ringing.
3.
The measured current is inverted and can be scaled by using: Id=Vid/Rshunt.
Figure 8 Recommended probe connection with current shunt
Thermal design:
1.
GS66508B has a thermal pad at the bottom side for heat dissipation. The heat is transferred to the
bottom side of PCB using thermal vias and copper plane.
2.
A heatsink (35x35mm size) can be attached to the bottom side of board for optimum cooling.
Thermal Interface Material (TIM) is needed to provide electrical insulation and conformance to
the PCB surface. The daughter board evaluation kit supplies with a sample 35x35mm fin heatsink
(not installed), although other heatsinks can also be used to fit users’ system design.
3.
A thermal tape type TIM (Berguist
®
Bond-Ply 100) is chosen for its easy assembly. The supplied
heatsink has the thermal tape pre-applied so simply peel off the protective film and attach the
heatsink to the back of board as marked in Figure 3.
4.
Two optional mounting holes as shown in Figure 9 are provided for mounting customized
heatsink using screws.
5.
Using the supplied heatsink and TIM, the overall junction to ambient thermal resistance R
thJ-A
is
~
9
°
C/W
with 500LFM airflow.
6.
Forced air cooling is recommended for power testing.
VGL
VSL
VSW
BNC case
To oscilloscope
probe input (use
50
Ω
termination)
BNC tip
V
DS
V
GS
I
D
