Project Analog - August 2008 - (Page 8)

Considerations When Selecting the Proper MOSFET Driver for Your Application Contributed by Microchip Technology www.microchip.com IntroductIon As with any design decision, there are multiple variables involved when selecting the proper MOSFET driver for the MOSFET being used in your design. Parameters such as input-tooutput propagation delay, quiescent current, latch-up immunity and driver current rating must all be taken into account. This article will explore several of these parameters in detail. dIe SIze effect on Gate capacItance As can be expected, the larger the die size of the MOSFET, the larger the effective gate charge. For an illustration of this, browse through any manufacturer’s data book. By relating die size to total gate charge, you will find that, as die size increases, the total gate charge will also increase. As advances are made in silicon technology, new MOSFETs are produced that may have the same die size as an older device, but with a lower total gate charge. However, MOSFETs within the same silicon technology still follow the same general rule that as die size goes up, so does the gate charge requirement. Many suppliers today have also come out with “low gate charge” versions of MOSFETs that allow for faster switching times and lower gate charge losses. These devices allow application sto operate at higher speeds, with lower switching losses in the power MOSFET, as well as lower gate charge losses in the MOSFET driver. peak current drIve requIrementS Matching the MOSFET driver to the MOSFET in the application will primarily be based on how fast the application requires the power MOSFET to be tuned on and off (rise and fall time of the gate voltage). The optimum rise/ fall time in any application is based on many requirements, such as EMI 9conducted and radiated), switching losses, lead/ circuit inductance, switching frequency, etc. The speed at which a MOSFET can be turned on and off is related to how fast the gate capacitance of the Contents Viewpoint Gate Drive Schemes for Motor Control Applications Considerations When Selecting the Proper MOSFET Driver Power Modules for Variable-Speed Motor Control Analog news Microchip analog page Motor Control Design Center MOSFET can be charged and discharged. The relationship between gate capacitance, turn-on/turn-off time and the MOSFET driver current Sample center microchipDIRECT Reference designs/ app notes Technical training 8 · PrOjECT ANAlOG · VOluME 2 / NuMbEr 5 http://www.microchip.com http://www.microchip.com http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2125¶m=en026178 http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2125¶m=en026178 http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423

Table of Contents Feed for the Digital Edition of Project Analog - August 2008

Project Analog - August 2008 Contents Viewpoint About Project Analog Sponsor Gate Drive Schemes for Motor Control Applications Considerations When Selecting the Proper MOSFET Driver for Your Application Power Modules for Variable-Speed Motor Control Efficient Motor/Controls Save Terrawatt-Hours/Year Analog News Contact Microchip Treelink Microchip Advanced Parts Selector (MAPS)

Project Analog - August 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.