Critical loads often employ parallel-connected power supplies with redundancy to enhance system reliability. The MAX8555/MAX8555A are highly integrated, inexpensive MOSFET controllers that provide isolation and redundant power capability in high-reliability systems. The MAX8555/MAX8555A are used in 0.5V to 3.3V systems, and have an internal charge pump to drive the gates of the N-channel pass elements to (VCS+ + 5V).
During startup, the MAX8555/MAX8555A monitor the voltage drop across the external MOSFETs. Once VCS+ approaches or exceeds the bus voltage (VCS-), the MOSFETs are turned on. The MAX8555/MAX8555A feature a dual-purpose TIMER input. A single external resistor from TIMER to ground sets the turn-on speed of the external MOSFETs. Optionally, the TIMER input can be used as a logic enable input. Once the external MOSFET is turned on, these controllers monitor the load, protecting the bus against overvoltage, undervoltage, and reverse-current fault conditions. The MAX8555 is available with a 40mV reverse-current threshold, while the MAX8555A is available with a 20mV reverse-current threshold.
Overvoltage and undervoltage fault thresholds are adjustable and can be disabled. The current-limit trip points are set by the external MOSFETs' RDS(ON), reducing component count. An open-drain, logic-low fault output indicates if an overvoltage, undervoltage, or reverse-current fault occurs. The MAX8555 and the MAX8555A can shut down in response to a reverse-current fault condition as quickly as 200ns.
Both devices come in space-saving 10-pin µMAX or TDFN packages and are specified over the extended -40°C to +85°C temperature range.
Key Features
Applications/Uses
Simple, Integrated, and Inexpensive MOSFET Controllers
ORing FET Drive for 0.5V to 3.3V
Eliminate ORing Diode Power Dissipation
Provide N+1 Redundant Supply Capability for Highly Reliable Systems
Isolate Failed Short-Circuit Supply from Output BUS
Respond to Reverse Short-Circuit Current in 200ns
Adjustable Blank Time
Programmable Soft-Start
Logic Enable Input
Adjustable Overvoltage and Undervoltage Trip Points
Fault-Indicator Output
Space-Saving Packages
Point-of-Load Supplies
Power-Supply Modules
Rectifiers
Redundant Power Supplies in High-Availability Systems
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