Additional Information: Quick View Data Sheet for the MAX668 Quick View Data Sheet for the MAX4130 Technical Support: Power This circuit uses the MAX668 and a transformer (which will need about a 1:2:2:2 turns ratio) to make a flyback converter. The op amp inverts the feedback from both negative output voltages. In systems where cards are hot-plugged, it is desirable sometimes to extend the soft-start period beyond the time provided in the IC in order to control the surge current at turn-on. The circuit above uses four external components to extend the soft-start period of the MAX668 (the technique also applies to the MAX1856 inverting transformer flyback controller). C5 is a bypass capacitor for LDO and part of the standard circuit. R1 is the current-sense resistor. R9 and C9 filter the switching noise from the current-sense signal. In normal operation, the LDO output is 5V. The switching frequency is set to 250kHz, and the internal soft-start is 1024 clock cycles, or 4msec. R10 and R11 are added to force the current-sense input, CS+, into current limit (+100mV). C10 is the timing capacitor that works with R10 to decrease the extra voltage applied to CS+ over a period of time. As the extra voltage decreases, the allowed current limit increases. Therefore, in this example, the current limit is increased from zero to 90% of full scale over a 33msec period (3 x R10 x C10). The soft-start period is modified by changing C10. When power is removed, D4 resets the voltage on C10. 相关型号   APP 436: Nov 01, 2000 MAX4130 单/双/四路、宽带、低功耗、单电源、满摆幅输入/输出运算放大器 完整的数据资料 (PDF, 424kB) 免费样品 MAX668 1.8V至28V输入、PWM升压型控制器，µMAX封装 完整的数据资料 (PDF, 304kB) 免费样品 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)。 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   下载，PDF格式 (29kB)  AN436, AN 436, APP436, Appnote436, Appnote 436