Abstract: Maxim's PFM boost controllers offer high efficiency and low quiescent current; however, by externally adding a current mode signal into the feedback, the stability and output ripple are improved. This circuit connection requires no additional ICs or components versus the standard connection. A control scheme used in certain boost-controller ICs from Maxim (current-limited pulse-frequency modulation, or PFM), achieves high efficiency over a wide range of output current by combining the low quiescent current of PFM with the load-driving capability of pulse-width modulation (PWM). To provide current-mode control as well, simply connect the load, output filter capacitor, and lower feedback resistor to the current-sense pin (CS) instead of ground (Figure 1). Figure 1. This circuit adds current-mode operation to Maxim's current-limited PFM boost controllers without increasing the quiescent current. When operating with medium to heavy loads, the Figure 1 circuit exhibits lower output ripple and a more stable inductor current (Figure 2a) than do the standard application circuits represented by typical waveforms in Figure 2b. The improvements gained by these connections have no effect on the quiescent current and require no additional circuitry, but they do require separate input and output grounds as shown, connected only by RSENSE. Figure 2. The Figure 1 circuit's inductor-current and output-ripple waveforms (a) exhibit better stability and lower ripple amplitude than those of the standard operating configuration (b). This circuit achieves current-mode control by constantly monitoring the inductor current through RSENSE: via the field-effect transistor during tON (which depends on the magnitude of VIN), and via the diode and output filter capacitor during tOFF (minimum 2.3µs). Flowing through RSENSE, the inductor current creates a signal at CS that couples through the output filter capacitor and adds to the normal feedback signal at FB. Connecting the load between OUT and CS prevents this CS signal from adding to the ripple at VOUT. 我们期待您的反馈！ 喜欢？不喜欢？有待改善？或为我们提供建议？请与我们联系 — 我们将根据您的意见或建议改善我们的工作。 网页评价或提供建议 自动更新 需要自动接收最新发布的应用笔记吗？请订阅EE-Mail™ (English only)。 更多信息   APP 1170: Sep 10, 2002 MAX1771 12V或可调、高效率、低IQ、升压型DC-DC控制器 完整的数据资料 (PDF, 1.6MB) MAX471 精密的、高端电流检测放大器 完整的数据资料 (PDF, 136kB) MAX608 5V或可调、低电压、升压型DC-DC控制器 完整的数据资料 (PDF, 152kB) MAX660 CMOS单片电压变换器 完整的数据资料 (PDF, 208kB) MAX770 5V/12V/15V或可调、高效率、低IQ、升压型DC-DC控制器 完整的数据资料 (PDF, 216kB) MAX771 5V/12V/15V或可调、高效率、低IQ、升压型DC-DC控制器 完整的数据资料 (PDF, 216kB) MAX772 5V/12V/15V或可调、高效率、低IQ、升压型DC-DC控制器 完整的数据资料 (PDF, 216kB) MAX773 5V/12V/15V或可调、高效率、低IQ、升压型DC-DC控制器 完整的数据资料 (PDF, 216kB) MAX863 双路、高效率、PFM、升压型DC-DC控制器 完整的数据资料 (PDF, 312kB) MAX921 超低功耗、单/双电源比较器，内置1%精密电压基准 完整的数据资料 (PDF, 348kB) MAX933 超低功耗、低成本比较器、内置2%电压基准 完整的数据资料 (PDF, 176kB)   下载，PDF格式 (40kB)  AN1170, AN 1170, APP1170, Appnote1170, Appnote 1170