USER GUIDE
UG499: Si828x-AW-GDB Gate Driver Boards
Skyworks Solutions, Inc. • Phone [949] 231-3000 • [email protected] • www.skyworksinc.com
206359B • Skyworks Proprietary Information • Products and Product Information are Subject to Change without Notice
2
November 10, 2022
2. System Overview
The Skyworks Si828x-AW-GDB is a printed circuit reference design suitable for interfacing to Wolfspeed XM3 power modules.
The board contains isolated gate drive functions for high-side and low-side transistors in a half-bridge module configuration,
with gate biasing, isolated power supply, and fault indication. Figure 2 provides a Si828x-AW-GDB functional diagram. The
Si828x-AW-GDB is included in the Si828x-AAWB-GDB-KIT.
An I/O header (JT3) provides access to the differential high-side and low-side control signals as well as differential fault indica-
tor outputs and temperature sensor outputs. It also exposes single-ended inputs for power supply disable, transceiver
enable, and driver reset.
A digital transceiver converts the differential high-side and low-side PWM control signal inputs to the single-ended high-side
and low-side gate drive control signals. The transceiver also converts a frequency-encoded NTC (Negative Temperature Coef-
ficient) sensor output into a differential RTD signal and a single-ended signal representing the combined fault signals and
ready signals from the high-side low-side gate drivers into a differential fault signal.
There are two gate drivers on the Si828x-AW-GDB. The low-side isolated gate drive is achieved by the Si8284x Isolated Gate
Driver with Integrated DC-DC Converter. This device is driven by the single-ended low-side PWM signal and drives the gate of
a switching device, either high or low by means of NPN and PNP transistors which provide enhanced drive current. A DESAT
sensing pin provides a means of detecting switch desaturation and a soft shutdown circuit allows the switch to be shut down
in a controlled manner if desaturation is detected. The circuit includes an enhanced Miller Clamp feature to ensure switch
turn off is maintained in the presence of high slew rate drain/collector or source/emitter signals. Desaturation faults are indi-
cated via the /FLT pin. Operation is restored by toggling the /RST pin via the Reset signal on the JT3 I/O header.
Loss of gate drive supply results in a loss of the RDY signal both on the RDY pin and the combined differential /FLT output at
the header, but RDY is restored when the gate drive supply is restored.
The Si8284x also has a DC-DC controller function. This controller drives an external NMOS switch on the primary side of the
power transformer. The secondary side of the transformer forms both high and low-side driver supplies. These supplies are
+15 Vdc and -3.5 Vdc with a return between them and provide a total of 5 W between high and low-side sections. The high
side supplies are isolated from the low side supplies by the transformer. The DC-DC controller function may be shut down via
the PS-DISb input on the I/O header.
High-side isolated gate drive is achieved by the Si8285 Isolated Gate Driver. This device and its associated circuit provide the
same function as the Si8284 but without the DC-DC controller.
The DC power input to the board is protected from a reverse polarity connection via the P channel MOSFET gate biasing volt-
age UB2.
An RTD connector provides the connection to an external NTC (negative temperature coefficient) resistive sensor for mea-
surement of switch module temperature. The RTD resistance is converted to a frequency that is then isolated and sent to the
differential transceiver, which is converted to a differential signal accessed via the I/O header.
The
AN1362: Si828x XM3 Gate Driver Test Report
provides more detailed information and a complete schematic of the
Si828x-AW-GDB. It also includes test setup and performance data of the operations between the Si828x gate driver and the
XM3 SiC module on the
