Project Analog - April 2008 - (Page 20)

fig 1 standard loW-sidE drivErs arE tyPically ratEd for a MaxiMuM of 15 to 25 v, and thEy drivE sWitchEs (or transforMEr Windings) rEfErEncEd to thE ground lEvEl of thE inPut signal. fig 2 siMPlE drivErs can BE iMPlEMEntEd discrEtEly, But WhEn MorE advancEd fEaturEs arE nEEdEd, an ic drivEr can dElivEr thEM in onE Part instEad of sEvEral, MiniMizing sPacE, Easing dEsign and iMProving rEliaBility. this ExaMPlE has dual high-sPEEd inPuts that can BE configurEd to ProvidE EithEr invErting or noninvErting Polarity. Each of thE schMitt-triggEr inPuts has WEllcontrollEd thrEsholds, EithEr ttl (0.8 to 2.0 v) for coMPatiBility With loW-voltagE logic, or cMos (0.4 to 0.6 vdd) for BEttEr noisE iMMunity. WhEn a PoWEr suPPly dEsignEr usEs rc circuits at thE drivEr inPuts to sEt dElays BEtWEEn diffErEnt sWitchEs, oftEn lEss variation can BE achiEvEd With thE highEr cMos thrEsholds, also MaxiMizing convErtEr EfficiEncy. mon low-voltage driver type is the synchronous-buck driver, which adds input level shifting for the high-side switch as well as timing circuitry to prevent cross-conduction— sometimes dynamically adjusting the dead-time between switches to maximize efficiency. A third type is the “high-side” driver, for MOSFETs that operate with their reference nodes at voltages significantly higher than the ground reference of the input signal. Ratings as high as 625 V are common for these drivers. Simple drivers can be implemented discretely, but when more advanced features are needed, an IC driver can deliver them in one part instead of several, minimizing space, easing design and improving reliability. Some of these features can be seen in Fig. 2, an internal block diagram of a single-channel high-performance driver. Other visible features including undervoltage lockout, an “enable” function (using one of the dual inputs), and input pull-up/down resistors all Contents Viewpoint Calculating Power Dissipation Accelerating Amplifier Design Driving Power MOSFETs Analog news Microchip analog page MOSFET driver overview Sample center microchipDIRECT Reference designs/ app notes Technical training 20 · prOjECT ANAlOg · Apr 08 http://www.microchip.com http://www.microchip.com/analog http://www.microchip.com/analog http://www.microchip.com/mosfetdriver http://www.microchip.com/mosfetdriver 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

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Project Analog - April 2008 Contents Viewpoint About Project Analog Sponsor Calculating Power Dissipation in a MOSFET Driver Accelerating Design of >50-W Class D Amplifiers Driving Power MOSFETs in Switch Mode Power Supplies Synergistic MOSFET Solutions Trends in MOSFET Gate Drivers Analog News—Analog news from multiple sources Enter to win an iPhone Contact Project Analog Sponsor Treelink Microchip Advanced Parts Selector (MAPS)

Project Analog - April 2008

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