| Maxim MAX8792 PWM控制方案 |
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| 作者：未知 来源：Maxim 点击数：88 更新时间：2008-5-12 |
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Maxim公司的MAX8792是PWM控制器,具有要效率,极好的瞬态响应和高直流输出精度(精度达0.5%)的特性,支持的输入电压在0-2V之间,非常适合用在笔记本电脑,I/O和芯片组电源,GPU内核电源,DDR存储器,POL电源以及降压电源.本文介绍MAX8792的主要性能, 功能方框图, 标准应用电路以及高输出电压等应用电路.
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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