Abstract: In Telecom systems such as Radio Link and Point to Point, the point-to-multipoint controller shuts the system off in the event of a fault. When the fault is brief (for instance, a momentary short circuit due to measurement and calibration actions), the auto-retry controller attempts to restart the system. The MAX1637 (IC2 in Figure 1) is a popular device for telecom applications. It offers PWM operation, small size, high MOSFET-drive capability, wide VIN and VOUT ranges, and excellent protection against over- and under-voltage faults. Undervoltage is related to a short circuit: VOUT falls when a short circuit is present and the controller cannot regulate the supply voltage. If that voltage remains below 70% of its nominal value for 6144 clock cycles, IC2 latches and turns both devices off. To restart IC2, you must either switch off the power supply or toggle the active-low SHDN signal. Figure 1. The circuit adds auto-retry capability to IC2, thereby enhancing its usefulness for telecom and other applications. The microprocessor supervisor (IC1) includes an internal power-fail comparator and manual-reset circuitry (MR). IC1's PFI input detects whether VOUT (1.8V) is above the internal reference voltage (1.25V). If VOUT falls below 1.25V (due to a short circuit, for instance), the active-low PFO output generates a pulse using the internal 60k pull-up resistor and external 0.1µF capacitor. The pulse drives active-low MR low, causing active-low RST to assert and pull active-low SHDN low. After a timeout delay of 140ms, active-low RESET and active-low SHDN go high, re-enabling IC2. This supervision is also in effect when the supply voltage is first switched on: the 3.5V rail stabilizes after 140ms, causing active-low RST to go high and activate IC2. A similar version of this article appeared in the September 2, 2002 issue of Electronica magazine. 相关型号   APP 1987: Apr 14, 2003 MAX1637 微型、低电压、精密的、降压型控制器 完整的数据资料 (PDF, 312kB) 免费样品 MAX6342 6引脚、微处理器复位电路，带有电源失效比较器 完整的数据资料 (PDF, 556kB) 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 (21kB)  AN1987, AN 1987, APP1987, Appnote1987, Appnote 1987