Cut Your Losses–With an Active Diode

by Nazzareno (Reno) Rossetti, Steve Logan and Stuart Smith, Maxim Integrated, San Jose, Calif., How2Power Today, Sep 15 2017

Focus:
Schottky diodes are commonly used for ORing two or more power sources, which ensures that when one fails, the other intervenes. But in low-voltage applications, the supposedly low dropout voltage of the Schottky is not so low, leading to power losses, while the Schottky’s reverse leakage current can drain the main power source and try to charge a nonrechargeable battery. This article reviews ORing techniques used to switch between two power sources in four low- voltage applications, and introduces an ideal diode IC—the MAX40200—which overcomes the limitations of the existing techniques. Among the applications discussed, one involves use of an alkaline backup battery; another uses an auxiliary power source for redundancy; a third employs a wireless power source in combination with a USB power source; and the last uses a wall adapter and a Li-ion battery.

What you’ll learn:

• How to overcome limitations of Schottky diodes for ORing power sources in low-voltage applications

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