Usb-powered Dsl Modem Supply

Abstract: The MAX1896 MAX1973 and MAX8863 combine to deliver 5V at 225mA, 1.8V at 220mA, and 3.3V at 60mA from a USB port. The schematics, BOM and performance data appear below. USB devices draw power from the USB port. The voltage is 4.5V to 5.25V and the current is limited initially to 100mA maximum. After enumeration, the current limit may be increased to 500mA maximum. Therefore, the practical power consumption is limited to about 2W at 4.5V. Switching power supplies are preferred so that this limited power CAN be fully utilized. The DSL frequency band extends to about 1.1MHz. To maintain maximum data throughput in DSL modems, the fundamental switching frequency should be 1.2MHz or higher. The MAX1896 MAX1973 and MAX8863 combine to deliver 5V at 225mA, 1.8V at 220mA, and 3.3V at 60mA from a USB port. The schematics, BOM and performance data appear below. The MAX1896 is a Step-up Regulator configured as a SEPIC that switches at 1.4MHz. The MAX1973 is a Step-down Regulator that switches at 1.4MHz. The MAX8863 is a 100mA linear Regulator Each has a shutdown control to facilitate USB port enumeration and standby mode. The total input current required at 4.5V input to provide maximum output power is less than 491mA. The overall efficiency is 79.8% for 1.76W output at 4.5V input. The tallest component is the 3.3µH Sumida inductor at 1.8mm maximum.
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Usb-powered Dsl Modem Supply application circuits
Usb-powered Dsl Modem Supply application circuits



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