Project Analog - April 2008 - (Page 15)

tc4423a/24a/25a MosfEt drivErs The TC4423A, TC4424A and TC4425A devices are a family of dual-output 3A buffers/MOSFET drivers. These drivers can easily charge and discharge 1800 pF gate capacitance in under 20ns, provide low enough impedances in both the on and off states to ensure the MOSFET’s intended state will not be affected, even by large transients. Applications: • Switch Mode Power Supplies • Pulse Transformer Drive • Line Drivers • Direct Drive of Small DC Motors from the use of dedicated MOSFET drivers (Figure 2). The synchronous step-down converter shown is common for CPUs requiring greater than 6A of DC current. It also accommodates custom voltages not accommodated by the current “silver box” supplies. Efficiency is not as large a concern, since this supply is line-powered. The topology shown is simpler than that of Figure 1. The TC4428A serves as a high-side/low-side driver powered from the same VDD. N-Channel MOSFETs are used to save cost. The TC4428A has sufficient output current to drive a 10A (continuous drain current) MOSFET active in 25 ns. conclusion Using dedicated MOSFET drivers results in a more optimized SMpS design. sophistication, low output power designs. External drivers fashioned from discrete active and passive components have neither the repeatable high performance, nor the low cost of a dedicated monolithic driver circuit. Dedicated drivers like those offered by Microchip Technology feature fast rise, fall and delay times, and are available in a wide variety of topologies to suit virtually every application. Contents Viewpoint Calculating Power Dissipation Accelerating Amplifier Design Driving Power MOSFETs Analog news • TC4431, which has a peak capability of 1A. They can drive MOSFETs capable of 10A continuous drain current in 30 ns. desktoP Pc Power suPPly Desktop power supplies also benefit 15 · prOjECT ANAlOg · Apr 08 Power MOSFETs are desirable as switching elements in SMPS designs because of their low onresistance and high current carrying capability. Using dedicated MOSFET drivers results in a more optimized SMPS design. Drivers integrated on-board the SMPS controller are advantageous only for low Microchip analog page MOSFET driver overview Sample center microchipDIRECT Reference designs/ app notes Technical training 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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