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Simplest, Smallest ORing MOSFET Controllers With Fastest Reverse Current Protection

The manufacturer says...

Chipcenter's Nasser Kutkut, Ph.D., says...

Maxim Integrated Products introduced the MAX8535/MAX8536, the fastest and smallest ORing MOSFET controllers to provide fault isolation and redundant power capability in high-reliability systems. These controllers eliminate the high power dissipation and reverse leakage problems associated with ORing diodes. The simplicity and robustness of the MAX8535/MAX8536 make them ideal for redundant supplies in high-availability systems, rectifiers, and silver-box power supplies in servers and networking applications. When a reverse-current flow is detected through the ORing MOSFET, the MAX8535/MAX8536 isolates the failed input supply in less than 1 µs. Furthermore, when input under/overvoltage is detected, both controllers selectively isolate the faulty supply and maintain a stable bus voltage. The MAX8535 is suitable for 12 V applications, while the MAX8536 is suitable for 3.3 V or 5 V applications. Both controllers feature a dual-purpose programmable timer allowing adjustable soft-start or use as a logic enable. The MAX8535/MAX8536 provide lossless current sensing and offer reverse current protection, as well as adjustable over/undervoltage detection. Overvoltage, undervoltage, or reverse-current conditions are indicated by a versatile FAULT output. The MAX8535EUA/MAX8526EUA are available in a space-saving 8-pin µMAX package. Prices start at $1.50 (1000 up, FOB U.S.A.). Both controllers are specified for the extended-industrial temperature range (-40°C to +85°C). An evaluation kit is available to speed designs.

Diodes are the simplest and preferred ORing devices used in many power-supply applications. With diodes, no control is needed, and an endless number of units can be easily ORed. However, diodes suffer from certain drawbacks, including significant forward power dissipation and reverse leakage problems, which limit their use in highly available redundant power supplies. Maxim's new ORing MOSFET controllers circumvent the drawbacks of ORing diodes by offering lower power dissipation and minimal reverse current flow, all in space-saving power packages. The added control functionality expands the operation of these MOSFET controllers to include protection against under/overvoltage as well as lossless current sensing and reverse current protection. Designers looking for better ORing solutions should consider these smarter and highly efficient ORing controllers.

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