The MAX5921/MAX5939BESA hot-swap controllers allow a circuit card to be safely hot plugged into a live backplane. The MAX5921/MAX5939BESA operate from -20V to -80V and are well suited for -48V power systems. These devices are pin compatible with both the LT1640 and LT4250 and provide improved features over these devices. The MAX5921/MAX5939BESA provide a controlled turn-on to circuit cards preventing damage to board connectors, board components, and preventing glitches on the power-supply rail. The MAX5921/MAX5939BESA provide undervoltage, overvoltage, and overcurrent protection. These devices ensure that the input voltage is stable and within tolerance before applying power to the load. Both the MAX5921 and MAX5939BESA protect a system against overcurrent and short-circuit conditions by turning off the external MOSFET in the event of a fault condition. The MAX5921/MAX5939BESA protect against input voltage steps by limiting the load current to a safe level without turning off power to the load. The device features an open-drain power-good status output, active-low PWRGD or PWRGD for enabling downstream converters (see Selector Guide). A built-in thermal shutdown feature is also included to protect the external MOSFET in case of overheating. The MAX5939BESA features a latched fault output. The MAX5921 contains built-in autoretry circuitry after a fault condition. The MAX5921/MAX5939BESA are available in an 8-pin SO package and operate in the extended -40°C to +85°C temperature range.
Feature
- Allows Safe Board Insertion and Removal from a Live -48V Backplane
- Pin-Compatible with LT1640 and LT4250
- Circuit Breaker Immunity to Input Voltage Steps and Current Spikes
- 450mA GATE Pulldown Current During Short-Circuit Condition
- Exponential GATE Pulldown Current
- Withstands -100V Input Transients with No External Components
- Programmable Inrush and Short-Circuit Current Limits
- Operates from -20V to -80V
- Programmable Overvoltage Protection
- Programmable Undervoltage Lockout with Built-In Glitch Filter
- Overcurrent Fault Integrator
- Powers Up into a Shorted Load
- Power-Good Control Output
- Thermal Shutdown Protects External MOSFET
Applications
- Base-Station Line Cards
- Central-Office Line Cards
- Network Routers and Switches
- Server Line Cards
- Telecom Line Cards
