A chipset from International Rectifier joins the company's XPhase family of control and phase ICs for scalable multiphase, interleaved buck dc-dc converters. It adds N+1 redundancy, hot swapping, and other protection features. The chipset, comprising the IR3510 XPhase Control IC and IR3086A and IR3088A Phase ICs, targets high-availability CPUs and servers in fault-tolerant applications needing live-insertion capability.

The IR3510 control IC implements a synchronous buck topology, combined with input MOSFETs for hot-swapping and output MOSFETs for Oring. The architecture ensures complete system protection against failures such as short circuits. The use of average current mode control extends MTBF by implementing droop sharing between converters, thus eliminating single-point failure modes for N+1 redundancy. Additionally, the chipset gives input isolation protection for hot swapping of power modules without damaging them.

Hot swappable N+1 redundant ac-dc and dc-dc converters using transformer-based power topologies have been available for several years for board-level bulk power in server, telecommunication, and netcom systems. But the lower operating voltages, higher currents, and proliferation of power rails in advanced microprocessors make transformer-based topologies unsuitable for directly powering the devices. Until now, point-of-load converters gave N+1 redundant power along with input-to-output isolation.

Xphase's distributed multiphase architecture consists of control and phase ICs that communicate using a simple five-wire bus scheme. Engineers can add or remove phases without changing the fundamental design. The five-wire analog bus consists of bias voltage, phase timing, average current, error amplifier output, and VID voltage. By eliminating point-to-point wiring between the control and the phase ICs, the five-wire bus shortens interconnections, reduces parasitic inductance and noise, and simplifies PCB layout.

International Rectifier,
El Segundo, Calif.,