Smart way to cut down hot swap power protection

Smart HotPlug is a new series of smart, highly integrated devices that simplify the implementation of hot swap power protection.

Smart HotPlug is a new series of smart, highly integrated devices that simplify the implementation of hot swap power protection on boards that are regularly switched in and out of powered-up computing and telecomms systems.

These rugged and reliable new devices - ideal for distributed power systems, high availability servers, disk arrays and powered board insertion -- help eliminate costly down-times due to bus glitches, overloads or short circuits.

The NIS5101 is the first Smart HotPlug device in a family of integrated hot-swap protection circuits ON Semiconductor is scheduled to launch this year.

This debut device is designed to allow safe insertion and removal of electronic equipment to -48V backplanes.

While there are a number of hot-swap controllers on the market, the NIS5101 is the only device available with a low 40mohm, 110V rated integrated smart mosfet.

By integrating a smart mosfet with a current mirror into the NIS5101 - specifically a SenseFET - only a fraction of the load current is sensed across the sense resistor.

This eliminates the need for a larger and more expensive external power sense resistor and lowers the sensing power dissipation.

The internal mosfet temperature sensing circuit protects it from overheating.

An adjustable current limiting feature enables the designer to set the maximum inrush current from 12 to less than 1A.

Undervoltage and overvoltage lockouts prevent the load from "seeing" a potentially unsafe operating voltage.

This device can run at a 5A continuous current with only a 0.3in2 copper pad and no additional heatsink or airflow.

With additional copper, heatsink or air flow, it can be operated at a higher average current.

Until now the best hot-swap solution for -24 or -48V distributed power systems has been the implementation of a cumbersome multiple-device solution that includes a power mosfet, a power sense resistor and an analogue controller.

Up to 14 additional active and passive components have been needed around the controller to achieve an effective hot-swap solution.

In comparison, the NIS5101 requires only three external components for complete hot-swap protection - specifically three low-power resistors to set current limit, overvoltage trip points, and undervoltage trip points.

(If an overvoltage trip point is not required, only two resistors and the NIS5101 Smart HotPlug device are required).

To address thermal sensing, the NIS5101 has integrated temperature-sensing diodes that deliver highly accurate thermal protection.

Competitive devices estimate the mosfet junction temperature for thermal protection - an IC design architecture that can result in catastrophic mosfet failure or the nuisance of early tripping the overcurrent circuit.

"The NIS5101 is the industry's first hot-swap device to deliver such ease of design in so compact and robust of a device", said Ramesh Ramchandani, ON Semiconductor Vice President and General Manager of Integrated Power Devices Division.

"Compared to the best competitive solution out there, ON Semiconductor's Smart-Hot-Plug devices cut hot-swap circuit design-time in half and require 75% fewer external components to achieve a complete and efficient hot swap solution".

The NIS5101 - with either latch-off or auto-retry thermal options - is available in a D2Pak priced at $2.80 per unit in 10,000-unit quantities and in the seven-lead SPak for $2.90 per unit in 10,000-unit quantities.

Samples and demo boards can be ordered online.

Back to top