DirectFET™ Solves Difficult Design Challenges |
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The International Rectifier DirectFET™ power MOSFET is uniquely positioned to enable today's design engineer to solve challenging design problems with it unrivaled efficency and power density.
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The DirectFET™ Design Advantage
- Is higher current or power density important to your new product designs?
- Is a low profile of less than 1 mm important in your new high-density power conversion circuits?
- Is lower package inductance important to achieve the desired performance in your advanced power conversion circuits?
- Has the power dissipation of your new power conversion circuits grown past the level offered by industry standard packages?
- Is it necessary to place components on both sides of the PCB (Printed Circuit Board) to achieve the circuit density required for your newest systems?
- Have you ever observed any problems when trying to operate MOSFETs in parallel such as some parts over heating, parts turning on at different times due to differences in threshold or the devices being at different temperatures?
- Is a lower junction temperature important in your power conversion circuits?
- Are you using surface mount components in your power circuits now? If so, what types?
- Are you already using heat sinks to remove the excess heat from your power circuits?
- What type of airflow is available to cool your power circuits?
1.
The largest benefit of International Rectifier's DirectFET™ products is that they have consistently demonstrated the highest power and current density in sync buck circuits.
These technical articles describe how:
- DirectFET™ Power Density PDF
- High Current Voltage Regulator Module Emplys Novel Packaging Technology to Achieve Over 100A in a Compact Footprint to Power Next Generation Servers PDF
- Novel Power MOSFET Packaging Technology Doubles Power Density in Synchronous Buck Converters for Next Generation Microprocessors PDF
- DirectFET™ Technology: Board Mounting Guidelines PDF
- Understanding the Effect of Power MOSFET Package Parasitics on VRM Circuit Efficiency at Frequencies Above 1MHz PDF
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2.
If a height limitation is an issue in your power conversion circuit, then consider the following: in most electronic equipment, there is 1 mm clearance between the back of a PCB and the chassis. If your design plans to use this space, then the low profile of the DirectFET™ makes it the best power package for your application.
Additionally, in many applications, the overall height of the component and heatsink is limited; the low profile of the DirectFET™ allows the heatsink to be larger, further improving the excellent thermal impedance already found in the DirectFET™.
These technical articles describe how:
- DirectFET™ Technology: Board Mounting Guidelines PDF
- Novel Power MOSFET Packaging Technology Doubles Power Density in Synchronous Buck Converters for Next Generation Microprocessors PDF
- Understanding the Effect of Power MOSFET Package Parasitics on VRM Circuit Efficiency at Frequencies Above 1MHz PDF
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3.
In many new power conversion circuits, the designer uses higher frequencies to achieve higher power densities by shrinking the size of the inductor and reducing the number of capacitors needed to store energy while the regulator feedback loop catches up to changes in load current demand.
Recent circuits have demonstrated that the lower package inductance of the DirectFET™ reduces the peak voltage spike during transients, allowing a 30-volt part in a traditional package to be replaced with a 20 volt DirectFET™. This offers two options:
- The use of a smaller, lower cost part can be incorporated into your design.
- The same size part can be used to reduce the on resistance of the part and increase the current carrying ability of the circuit.
These technical articles describe how:
- Understanding the Effect of Power MOSFET Package Parasitics on VRM Circuit Efficiency at Frequencies Above 1MHz PDF
- Press release for IRF6607 + IRF6604 PDF
- DirectFET™ Technology: Board Mounting Guidelines PDF
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4.
In new high-density circuits, the DirectFET™ products have demonstrated an ability to replace two standard products with a single DirectFET™. In sync buck circuits this allows two high side control FETs to be replaced by a single FET, reducing the switching loses by 50% of more. This results in significant increase in efficiency.
The DirectFET™ products allow a heatsink to be mounted directly to the top of the MOSFET that is usually the hottest component. This allows the heat from the MOSFET to removed away from the PCB directly into the airflow, resulting in a lower PCB temperature for all the remaining parts mounted on the PCB.
If very high power density is required, a heat pipe or other high performance heat sink can be mounted above the DirectFET™ product with only a thin layer of thermal compound between the 'can' and sink keeping the thermal impedance junction to ambient lower than other alternatives.
These technical articles describe how:
- Novel Power MOSFET Packaging Technology Doubles Power Density in Synchronous Buck Converters for Next Generation Microprocessors PDF
- DirectFET™ Performance: Thermal and In-Circuit HTML
- VRM10.x XPhase™/DirectFET™ High Efficiency Demo Board (DB3C)PDF
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5.
This is another way to exploit the advantages of the very low profile of the DirectFET™. In some applications, this has allowed the DirectFET™ products to be mounted where no active components could be, utilizing space that otherwise could not be used, greatly increasing the overall power density of the circuit.
This type mounting, can be used even more efficiently if the DirectFET™ is heat sunk to the chassis allowing the heat to be removed to the outside rapidly with little cost impact.
These technical articles describe how:
- DirectFET™ Power Density PDF
- High Current Voltage Regulator Module Emplys Novel Packaging Technology to Achieve Over 100A in a Compact Footprint to Power Next Generation Servers PDF
- Novel Power MOSFET Packaging Technology Doubles Power Density in Synchronous Buck Converters for Next Generation Microprocessors PDF
- DirectFET™ Technology: Board Mounting Guidelines PDF
- Understanding the Effect of Power MOSFET Package Parasitics on VRM Circuit Efficiency at Frequencies Above 1MHz PDF
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6.
One of the major advantages of the DirectFET™ is that it often eliminates the need to parallel multiple MOSFETs, epically when used with the XPhase™ controller that allows any number of phases to be used to meet the total current.
A major problem when paralleling MOSFETs is to match the junction temperature of the MOSFETs. With the low thermal impedance of the DirectFET™, keeping the junctions at the same temperature is greatly simplified.
These technical articles describe how:
- VRM10.x XPhase™/DirectFET™ High Efficiency Demo Board (DB3C)PDF
- DirectFET™ Power Density PDF
- XPhase™/DirectFET™ VRM10.x Test Fixture (DB4C)PDF
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7.
Because the junction of the DirectFET™ is in contact with the PCB, there is very little temperature-rise above the board temperature when using DirectFET™ devices. This can reduce the conduction losses of the MOSFETs by as much as 3%.
The small size of the DirectFET™ offers the opportunity to significantly reduce the size of the board layout; this reduces the parasitic resistance of the PCB traces and reduces the heat dissipated in the board. In new circuits, where the current can be more than 100 amperes, this can reduce the heat 10°C below other parts with the same on resistance.
These technical articles describe how:
- High Current Voltage Regulator Module Emplys Novel Packaging Technology to Achieve Over 100A in a Compact Footprint to Power Next Generation Servers PDF
- Novel Power MOSFET Packaging Technology Doubles Power Density in Synchronous Buck Converters for Next Generation Microprocessors PDF
- DirectFET™ Technology: Board Mounting Guidelines PDF
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8.
If the existing part is an SO-8 and the current per phase is greater than 12 to 15 amperes, the DirectFET™ will offer a significantly lower system cost.
If the existing solution is a Power pak, or other enhanced SO-8 and the current is greater than 15 to 17 amperes the DirectFET™ will offer a lower cost solution if the performance is matched, or offer higher performance at a similar cost.
If the existing solution is a TO-220 with a heat sink, the DirectFET™ will offer a significantly smaller solution at a very slight price increase. If higher performance in a smaller design is important, then DirectFET™ is the option to consider.
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9.
In the past, some designers have begun to design in the DirectFET™, only to get feedback from manufacturing that adding a heat sink was an additional step and would increase the cost of production. It is possible to confirm that the advantages of adding a simple heatsink mounting step into the production will result in a significantly lower overall system cost.
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10.
There are advantages when using airflow and heat sinks to shrink the overall size of power conversion circuits.
The more the cooling is improved, the advantages of the DirectFET™ increase.
In situations with low airflow and small board space, there will be very little performance difference between our SO-8 devices and the DirectFET™. In these cases, we recommend that our newest SO-8 devices be used as the lowest cost alternative unless the operating temperature is high enough that the small improvement of the DirectFET™ will keep the junction within required limits.
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IR's proprietary DirectFET™ technology is covered by US Patent 6,624,522 and other US and foreign pending patent applications
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