SiC Power Device｜Application
Points to be Noted Relating to Board Wiring Layout Key Points of This Article
2024.07.24
Points of this article
・Because pin assignments are different for products in TO-247-4L packages having a driver source pin and TO-247N package products not having a driver source pin, care must be taken in the pattern layout.
・In the case of the TO-247-4L package, due to the pin assignment, lines necessarily cross when connecting to the gate driver, so that the wiring cannot be laid out on the same surface. Hence there are two loops formed, for the OUT signal and for the GND2 signal, and surges may occur depending on the loop areas and the ratio of the areas.
・As countermeasures, the loop areas can be made as small as possible, and the areas of the loops (1) and (2) can be made equal. Also, the addition of a basic surge suppression circuit, as well as a snubber circuit, should be studied.
This article concerns points to keep in mind relating to the board wiring layout when using products in the TO-247-4L package, which has a driver source pin. Because the pin assignment for the TO-247-4L package differs from that for conventional packages, some care must be taken in the wiring layout.
Points to be Noted Relating to Board Wiring Layout for TO-247-4L Packages with a Driver Source Pin
As indicated in “Packages Provided with Driver Source Terminals“, pin assignments for the TO-247-4L package with a driver source pin differ from those for the conventional TO-247N package. The pin assignments of the conventional TO-247N package and of the TO-247-4L and TO-263-7L packages, which have driver source pins, are again shown below.
The gate pin of the TO-247-4L package is the rightmost pin when facing the marked surface, but the gate pin of the conventional TO-247N package is the first pin on the left side. MOSFETs are normally driven by a driver IC, and nearly all driver ICs have pin assignments that are suited to the TO-247N, which is a commonly used package. Below are shown examples of MOSFET connection diagrams when using the ROHM BM61S40RFV-C driver IC.
In the case of the TO-247N, the MOSFET driving signal OUT and the return signal GND2 are in the same order as the gate pin and the source pin, and so the wiring for both can be in parallel on the same surface.
In the case of the TO-247-4L package, on the other hand, the gate pin and driver source pin are in the opposite order of the driver IC pins, so that as shown in the diagram, the lines cross, and a wiring layout on the same surface is not possible. Hence two loops are formed, by the OUT signal and by the GND2 signal, as shown in the diagram; and attention must be paid to the ratio of the areas of the loops (1) and (2).
In general, MOSFETs in TO-247-4L packages are used in environments in which dID/dt is high. When changing flux (dΦ/dt) due to current changes is orthogonal to the area of a loop, an emf that is proportional to the driving circuit loop area is generated. Depending on the ratio of these loop areas, a positive or negative surge–a voltage that can cause a malfunction–may occur between the MOSFET gate and source. Hence it is necessary to make the areas of the loops formed for the OUT signal and the GND2 signal as small as possible, and the areas of the loops (1) and (2) must be made equal.
Moreover, the order of the pins for the TO-263-7L package is the same as that for the TO-247N, so that two loops are not formed unlike with the TO-247-4L. Hence the same approach to wiring as in the past can be used. However, the ROHM driver IC is provided with GND2 pins on both sides (pin 1 and pin 5) of the OUT pin that is the driving signal, and so the conventional wiring approach can be used even with devices in the TO-247-4L package.
In a number of previous articles, the addition of a VGS surge suppression circuit was recommended. Even so, however, ringing upon VDS turn-off can cause a VGS surge that exceeds the VGS rating. In such cases, by either lowering the impedance of the line from HVdc or by using a surge countermeasure such as a snubber circuit with each MOSFET, VGS surges can be kept to within the rated value. For information on designing snubber circuits, please refer to the “Snubber Circuit Design Methods” application note.
【Download Documents】 Basics of SiC Power Devices
This handbook explains the physical properties and advantages of SiC, the differences in characteristics and usage of SiC Schottky barrier diodes and SiC MOSFETs with a comparison to Si devices, and includes a description of full SiC modules with various advantages.
SiC Power Device
Basic
- What are SiC Schottky barrier diodes? ? Introduction
- What are SiC-MOSFETs? – SiC-MOSFET Features
- What are Full-SiC Power Modules?
- Summary
- Introduction
- What is silicon carbide?
Application
-
Introduction
- SiC MOSFET Bridge Configuration
- SiC MOSFET Gate Driving Circuit and Turn-On/Turn-Off Operation
- Currents and Voltages Occurring Due to Switching in Bridge Circuits
- Behavior of the Gate-Source Voltage During Low-side Switch Turn-on
- Behavior of the Gate-Source Voltage During Low-side Switch Turn-off
- Summary
- SiC MOSFETs: Method for Determining Losses from Switching Waveforms
-
SiC MOSFETs： Snubber Circuit Designs ーIntroductionー
- Non-Discharge RCD Snubber Circuit Design
- Surges Occurring between Drain and Source
- Types and Selection of Snubber Circuits
- C Snubber Circuit Design
- RC Snubber Circuit Design
- Discharge RCD Snubber Circuit Design
- Non-Discharge RCD Snubber Circuit Design
- Differences in Surge Occurrence Depending on Package
- SiC MOSFETs： Snubber Circuit Designs ーSummaryー
- Points to Note When Measuring SiC MOSFET Gate-Source Voltages: General Measurement Methods
-
Conventional MOSFET Driving Method
- Packages Provided with Driver Source Terminals
- Differences Made by and Benefits of a Driver Source Pin
- Benefits of a Driver Source Terminal: Comparisons Using Double Pulse Tests
- Behavior of Gate-Source Voltages when in a Bridge Configuration: Behavior at Turn-on
- Behavior of Gate-Source Voltages when in a Bridge Configuration: Behavior at Turn-off
- Points to be Noted Relating to Board Wiring Layout Key Points of This Article
- Verification of Loss Reduction Using Latest-Generation SiC MOSFETs
- About Surges in Gate-Source Voltages
Product Information
- SiC Schottky Barrier Diodes
- SiC MOSFET
- SiC Power Modules
- SiC Schottky barrier diode Bare Die
- SiC MOSFET Bare Die
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