MAX8555A

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 (V_CS+ + 5V).

During startup, the MAX8555/MAX8555A monitor the voltage drop across the external MOSFETs. Once V_CS+ approaches or exceeds the bus voltage (V_CS-), 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 of MAX8555A 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 reversecurrent fault condition as quickly as 200ns.

MAX8555A come in space-saving 10-pin µMAX or TDFN packages and are specified over the extended -40 to +85 temperature range.