Harris Semiconductor has expanded its family of hot plug controllers with the addition of a new integrated circuit designed specifically for Redundant Array of Independent Disk (RAID) systems. Harrisı new HIP1012 controller is a dual-supply power distribution controller that safely removes and applies power to a disk drive, allowing RAID systems to continue to function during service operations.

The HIP1012 offers dual functionality by providing accurate over-current protection through active current limiting on both +5V/12V and +3.3V/5V power supply busses. Harrisı HIP1012 has a timeout feature which delays the protective over-current trip until the condition has existed for a pre-programmed interval, thus avoiding nuisance trips. If the timeout period expires and the over-current condition still exists, the HIP1012 simultaneously disconnects both loads from their power supplies. In the event of a current load greater than three times the current limit level, the IC immediately latches the power switches off, thus offering two levels of system protection.

Harrisı HIP1012 offers programmable current regulation and a programmable turn-on ramp. The device is also equipped with an internal charge pump, which means that designers can utilize more widely available and less costly N-channel MOSFETs to control both power supplies.

Applications

The new HIP1012 features make it useful in a variety of hot swap applications requiring dual supply control with high-accuracy current limiting. Beyond applications in RAIDs, the HIP1012 is well-suited for other hot swap functions such as hardware components, fans, power supplies, 3.3V and 5V digital logic power distribution control, and other 5V/12V or 3.3V/5V applications.

Isn't it strange that the main area of computing where you know power is not going to be removed while you work on problems is the one area that has not had dedicated hot swap protection offered? The standard over-current protection from the device is a nominal 100 mV on the rails but an even tighter 50 mV part is also available as the HIP1012A. These limits are extremely important in a RAID system where the concern has to be not only for the card that is being replaced or removed -- generally what most hot swap ICs are doing -- but most particularly to keep the rest of the system functional while that work is taking place.

I love the two levels of protection with a time delay on lower-level problems and an instantaneous shutdown on 3x problems. Putting the charge pump on board was a stroke of genius for controlling higher supply voltages with bread-and butter n-channel devices, and the programmable turn-on ramp means that every card and every application can be treated differently, as they should be. The protection is clearly worth the price. These parts will do extremely well and may wake up a couple of other suppliers. I'm sure they will be designed into non-RAID systems as well. The 100-mV HIP1012 is priced at $4.85 in 1000-piece lots, while the 50-mV HIP1012A is priced at $5.57, also in 1000-piece lots. Both parts are in 14-pin SOICs and both are in production. Harris also offers two evaluation boards ı the HIP1012EVAL1 for general purpose applications and HIP1012EVAL2 for RAID applications.