Analog Devices

The LTC4251B/LTC4251B-1/LTC4251B-2 negative voltage Hot Swap™controllers allow a board to be safely inserted and removed from a live backplane. Output current is controlled by three stages of current limiting: a timed circuit breaker, active current limiting and a fast feedforward path that limits peak current under worst-case catastrophic fault conditions.Programmable undervoltage and overvoltage detectors disconnect the load whenever the input supply exceeds the desired operating range. The supply input is shunt regulated, allowing safe operation with very high supply voltages. A multifunction timer delays initial start-up and controls the circuit breaker’s response time.The LTC4251B UV/OV thresholds are designed to match the standard telecom operating range of –43V to –75V. The LTC4251B-1 UV/OV thresholds extend the operating range to encompass –36V to –72V. The LTC4251B-2 implements a UV threshold of –43V only. The LTC4251B improves the ruggedness of the LTC4251 shunt regulator.UV/OVLTC4251–43V/–75VLTC4251-1–36V/–72VLTC4251-2–43V UV OnlyLTC4251B–43V/–75VLTC4251B-1–36V/–72VLTC4251B-2–43V UV OnlyApplicationsHot Board InsertionElectronic Circuit Breaker–48V Distributed Power SystemsNegative Power Supply ControlCentral Office SwitchingProgrammable Current Limiting CircuitHigh Availability ServersDisk Arrays

The LTC4252 negative voltage Hot Swap™controller allows a board to be safely inserted and removed from a live backplane. Output current is controlled by three stages of current limiting: a timed circuit breaker, active current limiting and a fast feedforward path that limits peak current under worst-case catastrophic fault conditions.Adjustable undervoltage and overvoltage detectors disconnect the load whenever the input supply exceeds the desired operating range. The LTC4252’s supply input is shunt regulated, allowing safe operation with very high supply voltages. A multifunction timer delays initial startup and controls the circuit breaker’s response time. The circuit breaker’s response time is accelerated by sensing excessive MOSFET drain voltage, keeping the MOSFET within its safe operating area (SOA). An adjustable softstart circuit controls MOSFET inrush current at start-up.The LTC4252-1/LTC4252A-1 latch off after a circuit breaker fault times out. The LTC4252-2/LTC4252A-2 provide automatic retry after a fault. The LTC4252A-1/LTC4252A-2 feature tight ±1% undervoltage/overvoltage threshold accuracy. The LTC4252 is available in either an 8-pin or 10-pin MSOP, while the LTC4252A is available in the 10-pin MSOP.UV/OV %Latch Off/RetryPackageLTC4252-14.6%Latch offMS-8, MS-10LTC4252-24.8%RetryMS-8, MS-10LTC4252A-11%Latch offMS-10LTC4252A-21%RetryMS-10LTC4252B-14.6%Latch offMS-8, MS-10LTC4252B-24.6%RetryMS-8, MS-10LTC4252C-11%Latch offMS-10LTC4252C-21%RetryMS-10ApplicationsHot Board InsertionElectronic Circuit Breaker–48V Distributed Power SystemsNegative Power Supply ControlCentral Office SwitchingHigh Availability ServersATCA

The LTC4253/LTC4253A negative voltage Hot Swap™controllers allow a board to be safely inserted and removed from a live backplane. Output current is controlled by three stages of current-limiting: a timed circuit breaker, active current limiting and a fast feedforward path that limits peak current under worst-case catastrophic fault conditions. The LTC4253/LTC4253A latch off after a circuit fault.Adjustable undervoltage and overvoltage detectors disconnect the load whenever the input supply exceeds the desired operating range. The LTC4253/LTC4253A’s supply input is shunt-regulated, allowing safe operation with very high supply voltages. A multifunction timer delays initial startup and controls the circuit breaker’s response time. The circuit breaker’s response time can be accelerated by sensing excessive MOSFET drain voltage, keeping the MOSFET within its safe operating area (SOA). An adjustable soft-start circuit controls MOSFET inrush current at start-up.Three power good outputs are sequenced by an adjustable timer and two ENABLE inputs to enable external power modules at start-up or disable them if the circuit breaker trips. The LTC4253A features tight ±1% undervoltage/ overvoltage threshold accuracy. The LTC4253/LTC4253A are available in a 16-pin SSOP.NotesLTC4253LTC4253ARecommendLTC4253Bfor new designsLTC4253A-ADJRecommendLTC4253Bfor new designsLTC4253BApplications-48V Distributed Power SystemsNegative Power Supply ControlCentral Office SwitchingHigh Availability ServersDisk Arrays

The LTC4257-1 provides complete signature and power interface functions for a device operating in an IEEE 802.3af Power over Ethernet (PoE) system. The LTC4257-1 simplifies Powered Device (PD) design by incorporating the 25k signature resistor, classification current source, input current limit, undervoltage lockout, thermal overload protection, signature disable and power good signalling, all in a single 8-pin package. The LTC4257-1 includes a precision, dual level current limit circuit. This allows it to charge large load capacitors and interface with legacy Power over Ethernet systems while maintaining compatibility with the current IEEE 802.3af specification. By incorporating a high voltage power MOSFET onboard, the LTC4257-1 provides the system designer with reduced cost while also saving board space.The LTC4257-1 can interface directly with a variety of ADI DC/DC converter products to provide a cost effective power solution for IP phones, wireless access points and other PDs. Analog Devices also provides network power controllers for Power Sourcing Equipment (PSE) applications.The LTC4257-1 is available in the 8-pin SO and low profile (3mm x 3mm) DFN packages.ApplicationsIP Phone Power ManagementWireless Access PointsTelecom Power Control

The LTC4258 is a quad –48V Hot Swap™controller designed for use in IEEE 802.3af compliant Power Sourcing Equipment (PSE). It consists of four independent ports, each with output current limit, short-circuit protection, complete Powered Device (PD) detection and classification capability, and programmable PD disconnect using DC sensing. Used with power MOSFETs and passives as in Figure 1, the LTC4258 can implement a complete IEEE 802.3af-compliant PSE.The LTC4258 can operate autonomously or be controlled by an I2C serial interface. Up to 16 LTC4258s may coexist on the same data bus, allowing up to 64 powered Ethernet ports to be controlled with only two digital lines. Fault conditions are optionally signaled with theINTpin to eliminate software polling.External power MOSFETs, current sense resistors and diodes allow easy scaling of current and power dissipation levels and provide protection against voltage and current spikes and ESD events.The LTC4258 is available in a 36-pin SSOP package.Analog Devices also provides solutions for 802.3af PD applications with the LTC4257, LTC4257-1, and LTC4267.ApplicationsIEEE 802.3af Compliant Endpoint and Midspan Power SourcesIP Phone SystemsDTE Power Distribution

The LTC4259A-1 is a quad –48V Hot Swap™controller designed for use in IEEE 802.3af compliant Power Sourcing Equipment (PSE). It consists of four independent ports, each with output current limit, short-circuit protection, complete Powered Device (PD) detection and classification capability, and programmable PD disconnect using AC or DC sensing. Used with power MOSFETs and passives as in Figure 1, the LTC4259A-1 can implement a complete IEEE 802.3af-compliant PSE.The LTC4259A-1 can operate autonomously or be controlled by an I2C serial interface. Up to 16 LTC4259A-1s may coexist on the same data bus, allowing up to 64 powered Ethernet ports to be controlled with only two digital lines. Fault conditions are optionally signaled with a programmableINTpin to eliminate software polling.External power MOSFETs, current sense resistors and diodes allow easy scaling of current and power dissipation levels and provide protection against voltage and current spikes and ESD events.The LTC4259A-1 is available in a 36-pin SSOP package.We also provide solutions for 802.3af PD applications with the LTC4257, LTC4257-1 and LTC4267.ApplicationsIEEE 802.3af Compliant Endpoint and Midspan Power SourcesIP Phone SystemsDTE Power Distribution

The LTC4260 Hot Swap™controller allows a board to be safely inserted and removed from a live backplane. Using an external N-channel pass transistor, the board supply voltage can be ramped up at an adjustable rate. An I2C interface and onboard ADC allow monitoring of board current, voltage and fault status.The device features adjustable analog foldback current limit with latch off or automatic restart after the LTC4260 remains in current limit beyond an adjustable time-out delay.The controller has additional features to interrupt the host when a fault has occurred, notify when output power is good, detect insertion of a load card and power-up in either the on or off state.ApplicationsElectronic Circuit BreakersLive Board InsertionComputers, Servers

The LTC4261/LTC4261-2 negative voltage Hot Swap™controllers allow a board to be safely inserted and removed from a live backplane. Using an external N-channel pass transistor, the board supply voltage can be ramped at an adjustable rate. The devices feature independently adjustable inrush current and overcurrent limits to minimize stresses on the pass transistor during start-up, input step and output short conditions. The LTC4261 defaults to latch-off while the LTC4261-2 defaults to auto-retry on overcurrent faults.An I2C interface and onboard 10-bit ADC allow monitoring of board current, voltage and fault status. A single-wire broadcast mode is available to simplify the interface by eliminating two optoisolators.The controllers have additional features to interrupt the host when a fault has occurred, notify when output power is good, detect insertion of a board and turn off the pass transistor if an external supply monitor fails to indicate power good within a timeout period.ApplicationsAdvancedTCA SystemsTelecom Infrastructure–48V Distributed Power SystemsPower Monitors

The LTC4263 is an autonomous single-channel PSE controller for use in IEEE 802.3af compliant Power over Ethernet systems. It includes an on-board power MOSFET, internal inrush, current limit, and short-circuit control, IEEE 802.3af compliant PD detection and classification circuitry, and selectable AC or DC disconnect sensing. On-board control algorithms provide complete IEEE 802.3af compliant operation without the need of a microcontroller. The LTC4263 simplifies PSE implementation, needing only a single 48V supply and a small number of passive support components.Programmable on-board power management circuitry permits multiple LTC4263s to allocate and share power in multi-port systems, allowing maximum utilization of the 48V power supply—all without the intervention of a host processor. The port current limit can be configured to automatically adjust to the detected PD class. Detection back-off timing is configurable for either Endpoint or Midspan operation. Built-in foldback and thermal protection provide comprehensive fault protection.An LED pin indicates the state of the port controlled by the LTC4263. When run from a single 48V supply, the LED pin can operate as a simple switching current source to reduce power dissipation in the LED drive circuitry.The LTC4263 is available in 14-pin 4mm × 3mm DFN and 14-pin SO packages.ApplicationsIEEE 802.3af Compliant Endpoint/Midspan PSEsSingle-Port or Multi-Port Power InjectorsPower ForwardersLow-Port Count PSEsEnvironment B PSEsStandalone PSEs

The LTC4264 is an integrated Powered Device (PD) interface controller intended for IEEE 802.3af Power over Ethernet (PoE) and high power PoE applications up to 35W. By including a precision dual current limit, the LTC4264 keeps inrush below the IEEE802.3af current limit levels to ensure interoperability success while allowing for high power PD operation. The LTC4264 includes a field-proven power MOSFET delivering up to 750mA to the PD load while maintaining compliance with the IEEE802.3af standard. Complementary power good outputs allow the LTC4264 to interface directly with a host of DC/DC converter products. The LTC4264 provides a complete signature and power interface solution for PD designs by incorporating the 25k signature resistor, classification circuitry, input current limit, undervoltage lockout, thermal overload protection, signature disable and power good signaling.The LTC4264 PD interface controller can be used along with a variety of ADI's DC/DC converter products to provide a complete, cost effective power solution for high power PD applications.The LTC4264 is available in the space-saving low profile (4mm × 3mm) DFN package.Applications802.11n Access PointsHigh Power VoIP Video PhonesRFID Reader SystemsPTZ Security Cameras and Surveillance Equipment