Low-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control

The discharged filter capacitors of the circuit card provide low impedance to the live backplane. High inrush currents from the backplane to the circuit card can burn up connectors and components, or momentarily collapse the backplane power supply leading to a system reset. The MAX5955 and MAX5956 hot-swap controllers prevent such problems by gradually ramping up the output voltage and regulating the current to a preset limit when the board is plugged in, allowing the system to stabilize safely. After the startup cycle is completed, two on-chip comparators provide VariableSpeed/BiLevel™ protection against short-circuit and overcurrent faults, as well as immunity against system noise and load transients. In the event of a fault condition, the load is disconnected. The MAX5955B and MAX5956B must be unlatched after a fault, and the MAX5955A and MAX5956A automatically restart after a fault.

The MAX5955 and MAX5956 integrate an on-board charge pump to drive the gates of low-cost, external n-channel MOSFETs. The devices offer integrated features like startup current regulation and current glitch protection to eliminate external timing resistors and capacitors. These devices provide open-drain status outputs, an adjustable startup timer, and adjustable current limits. The MAX5955 provides output undervoltage/ overvoltage protection for each channel, while the MAX5956 provides undervoltage/overvoltage monitoring for each channel.

The MAX5955 and MAX5956 are available in a space-saving 16-pin QSOP package.