Hot swap controller in QFN package
25 November 2008
Linear Technology has launched a new dual Hot Swap controller.
Designed to protect boards with multiple load supply voltages ranging from 2.9V to 29V, the LTC4222 enables safe board insertion and removal from a live, two-supply backplane by controlling external N-channel MOSFETs to limit the inrush currents during power up.
When a board is plugged into a backplane, inrush currents can be large enough to create a glitch on the load supply, causing other boards on the bus to malfunction. An I2C interface and 10bit ADC allow users to query important information such as card currents, voltages or fault status and use it to assess the health and integrity of the power distribution network. This information can be used to determine a card’s power consumption, check for normal power operation or execute other card diagnostic functions. The dual channels, wide operating voltage, integrated I2C/ADC and wide array of features make the LTC4222 suitable for emerging high availability systems.
The LTC4222 ensures that during start-up, inrush currents are safely controlled using current foldback, Soft Start and dI/dt-limiting techniques. A 5% accurate circuit breaker threshold minimises power loss and overdesign of power supply requirements. Load currents are then monitored using the voltages sensed across current sense resistors and controlled by adjusting the MOSFET Gate-to-Source voltages accordingly without the need of external gate components. A CONFIG pin allows one to control both channels independently or simultaneously, giving users maximum flexibility to configure the Hot Swap operations for their application. Each channel is equipped with separate current foldback and configurable GPIO pins that ensure healthy output voltages are being provided to the loads and indicate whether or not power good conditions are maintained. Separate enable, overvoltage and undervoltage comparators are also available. Meanwhile, an I2C interface is provided to read the ADC registers, and allow the host to poll the LTC4222 and determine if faults have occurred.
The LTC4222 is offered in commercial and industrial versions, supporting operating temperature ranges from 0°C to 70°C and -40°C to 85°C, respectively. It can be ordered in either a compact 32pin 5mm x 5mm QFN package or a 36-lead SSOP.
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