ICs improve “either-OR” power dilemma
By Bill Schweber -- EDN, May 27, 2004
New ICs from Linear Technology and Intersil help you improve the OR function that multiple supply configurations need (Picture). The near-ideal LTC4412HV diode has forward-voltage drop that is one-tenth that of a Schottky diode, and the device replaces the use of diodes for the supply ORing function. This 2.5 to 36V IC lets you build more efficient load-sharing or automatic switchover power-supply systems by reducing diode-drop loss. It also includes a digital-control input and an open-drain status output in its SOT-23 package. You can use multiples of this $1.70 (1000) device for sharing and switching among more than two loads.
Intersil’s ISL6144 ORing FET-controller IC performs a similar function but for a different range. Operating from 10 to 75V, including 100V transient, this OR-diode replacement handles the higher voltages common in telecom and datacom applications. In contrast to a loss of 10 to 14W at 20A using a conventional diode for the OR function, the IC reduces losses to around 3W due to the low MOSFET on-resistance of 5 mΩ. The ISL6144 includes monitoring and protection features against short circuits, adjustable trip levels, 100-μsec MOSFET turn-off, and status indication. It’s available in a 5×5-mm QFN package and a 16-lead TSSOP, which meets UL requirements for high-voltage spacing. The IC sells for $2.60 (one to 999).
Linear Technology Corp, www.linear.com.
Intersil Corp, 1-408-935-4300, www.intersil.com.
