双1.4MHz的同步降压稳压器，支持USB Dying Gasp应用

摘要：一个安全的USB “垂死的喘息”关机需要一个本地的储能电容，电源设备，并延长运作有序关闭。一个5V USB “垂死的喘息”应用程序中的电路提供电源失效输出一个2.88ms的预警时间。特色的MAX1970/MAX1972降压与PFO的监管。

Maxim > App Notes > Battery Management Power-Supply Circuits
Keywords: dying gasp, USB, power-fail warning, power-fail output, PFO, PFO threshold, DC-DC converter, DC-DC converter efficiency, Dec 18, 2001
energy storage capacitor, step-down regulator

APPLICATION NOTE 891
Dual 1.4MHz Synchronous Buck Regulator Supports USB Dying Gasp
Applications


Abstract:A safe USB "dying gasp" shutdown requires a local energy storage capacitor to power the device and prolong operation
for orderly shutdown. A circuit for a 5V USB "dying gasp" application provides a power-fail output warning time of 2.88ms. The
MAX1970/MAX1972 step-down regulators with PFO are featured.

Many portable universal serial bus (USB) devices are powered from the USB port. Most of these devices need a power fail warning
to