Project Analog - February 2009 - (Page 15) mcP1602: 2 mhz, 500 ma, sWiTchiNg rEgulaTor WiTh PoWEr gooD As system performance and efficiency both continue to improve, that task has become increasingly difficult. Designers need to add more external components for a rising variety of functions from configuration issues such as selecting an operating frequency to how to start up or how to handle faults. Each additional component raises system BOM cost and increases design complexity. Accuracy is also a growing issue. Designers of analog control loops must deal with inherent bandwidth limitations and increased latency created by low-cost analog processes and by capacitors and resistors in the feedback loop. Not long ago, power supply designers needed to deliver 3.3 V to a load at 15 A. In present systems, designers need to deliver 1 V and below at 150 A. Sensitivity to noise margins at such low voltages and high currents has forced the industry to create more accurate solutions. Furthermore, analog feedback loops are typically complex. They can require anywhere from six to ten separate, highly sensitive components and further complicate board layout. Designers using digital controls can simply designate operating parameters, such as frequency by selecting a value from a register. Parameters are typically stored in memory so no additional components are required. Moreover, digital control circuits provide significantly better accuracy. Whereas a typical analog controller may offer tolerances as high as 15% to 25%, a digital control circuit might offer three percent accuracy, a significant improvement. digiTaL LimiTaTions Historically designers attempting to use digital instead of analog control schemes have faced two problems. The first was speed. If an output voltage goes low, an analog control loop can recognize the change and adjust the duty cycle relatively quickly. Response is limited only by the process and by the components in the feedback loop. Digital controllers must first feed the output voltage through an A/D converter, perform processing on the digital output, and then convert the signal back to analog. Traditionally, this response has been severely limited by the A/D converter throughput. Early controller implementations suffered from significant latency and required multiple output capacitors to compensate for that speed limitation. Managing the highspeed transients in today’s highperformance CPUs and GPUs proved exceedingly challenging. Secondly, early digital control schemes were costly relative to analog implementations. Designed for general markets that used complex multiloop power systems, most early generation digital controllers were over-designed for PC or server applications. System designers ended up paying for silicon they did not need. new advances But what if you designed digital controllers specifically for servers and PC designs for PC enthusiasts? Engineers at CHiL Semiconductor Contents Viewpoint Selecting the Right dc/dc Converter Selecting the Right Battery System Understanding the Buck Switchmode Power Converter Analog news · Low Quiescent Current: 45 µA · Low Stand-by Current: 0.1 µA · 2.0 MHz: small passive components · 4.7 µH & 4.7 µF · PFM/PWM Auto transition · Power Good Indicator · 2.7 to 5.5 V input voltage · Li-Ion, Li-Poly, NiCd, NiMH compatible · 0.8 to 4.5V Adjustable output voltage · 1.2, 1.5, 1.8, 2.5 and 3.3V fixed · 90% efficiency · UVLO- Under voltage lock out · Over temperature compensation · Over current protection microchip Technology, chandler, az reader/literature inquiries 888-mcu-mchP www.microchip.com/analog · High Output Current: 500 mA Microchip analog page Sample center microchipDIRECT Reference designs/ app notes Technical training 15 · PRojeCt ANAlog · VolUme 3 / NUmBeR 1 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://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/analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423
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