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| Maxim MAX8792 PWM控制方案 | |||||
作者：Maxim 文章来源：Maxim 点击数： 更新时间：2008-5-7  |
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The MAX8792 pulse-width modulation (PWM) controller provides high efficiency, excellent transient response, and high DC-output accuracy needed for stepping down high-voltage batteries to generate low-voltage core or chipset/RAM bias supplies in notebook computers. The output voltage can be dynamically controlled using the dynamic REFIN, which supports input voltages between 0 to 2V. The REFIN adjustability combined with a resistive voltage-divider on the feedback input allows the MAX8792 to be configured for any output voltage between 0 to 0.9 VIN. Maxim’s proprietary Quick-PWM™ quick-response, constant- on-time PWM control scheme handles wide input/output voltage ratios (low-duty-cycle applications) with ease and provides 100ns “instant-on” response to load transients while maintaining a relatively constant switching frequency. Strong drivers allow the MAX8792 to efficiently drive large synchronous-rectifier MOSFETs. The controller senses the current across the synchronous rectifier to achieve a low-cost and highly efficient valley current-limit protection. The adjustable currentlimit threshold provides a high degree of flexibility, allowing thermally compensated protection using an NTC or foldback current-limit protection using a voltage-divider derived from the output. The MAX8792 includes a voltage-controlled soft-start and soft-shutdown in order to limit the input surge current, provide a monotonic power-up (even into a precharged output), and provide a predictable powerup time. The controller also includes output fault protection—undervoltage and overvoltage protection—as well as thermal-fault protection. The MAX8792 is available in a tiny 14-pin, 3mm x 3mm TDFN package. For space-constrained applications,refer to the MAX17016 single step-down with 10A, 26V internal MOSFETs available in a small 40-pin, 6mm x6mm TQFN package. MAX8792主要特性: _ Quick-PWM with Fast Transient Response _ Supports Any Output Capacitor No Compensation Required with Polymers/Tantalum Stable with Ceramic Output Capacitors Using External Compensation _ Precision 2V ±10mV Reference _ Dynamically Adjustable Output Voltage (0 to 0.9 VIN Range) Feedback Input Regulates to 0 to 2V REFIN Voltage 0.5% VOUT Accuracy Over Line and Load _ 26V Maximum Input Voltage Rating _ Adjustable Valley Current-Limit Protection Thermal Compensation with NTC Supports Foldback Current Limit _ Resistively Programmable Switching Frequency _ Overvoltage Protection _ Undervoltage/Thermal Protection _ Voltage Soft-Start and Soft-Shutdown _ Monotonic Power-Up with Precharged Output _ Power-Good Window Comparator 应用: Notebook Computers I/O and Chipset Supplies GPU Core Supply DDR Memory—VDDQ or VTT Point-of-Load Applications Step-Down Power Supply  图1.MAX8792功能方框图  图2. MAX8792标准应用电路  图3.采用反馈分压器的高输出电压应用电路  图4.采用Foldback限流保护的标准应用电路 详情请见: http://datasheets.maxim-ic.com/en/ds/MAX8792.pdf |
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