Linear Technology Corp. (LTC, Milpitas, CA) introduced its new LTC4253 -48V hot-swap controller that protects telecom and high-availability server boards and also enables three dc/dc converters in sequence. Applications using distributed -48V over the backplane use separate dc/dc converters on each board to generate the local supplies. The LTC4253 allows these boards to be safely inserted or removed with no downtime.
The new controller features a circuit breaker that controls the primary current to the board in three ways. A slight over-current condition will trip the circuit breaker if it persists for a programmed timer period. Larger over-current conditions will be controlled through active current limiting, maintaining a safe power level in the MOSFET. Catastrophic over-current conditions due to a short-circuit will cause the fast comparator to trip immediately, protecting the load and the MOSFET even more quickly than the active current limit loop.
The LTC4253 voltage monitor features enhance the multi-level current control. The under- and over-voltage level monitor pins allow the user to define the operating voltage range for the system. The LTC4253 itself can operate from at least -15V to very high negative voltages due to its floating topology. Excessive drain voltage can be detected and this accelerates the circuit breaker's response time, keeping the MOSFET within its safe operating area.
The LTC4253 is offered in the 16-pin SSOP package and is screened to the commercial and industrial temperature ranges. Pricing starts at $2.95 each for 1,000-piece quantities.
