A fully integrated HDD power IC with novel head retract feature

Abstract

A fully-integrated motor-control servo power IC designed for driving small form factor hard disk drives (HDDs) is described. The "combo chip" IC features a novel head retract technique which eliminates the need for external Schottky diodes, yet guarantees the spindle motor's generated emf delivers uninterrupted power for emergency head retract operation. By eliminating the diode and its associated voltage drop, improved spindle motor startup current is achieved using smaller power MOSFETs. Other benefits of this approach include improved running efficiency, reduced head seek times, and increased time (and voltage margin) available to perform emergency head retract. The concept of an auxiliary supply is introduced, as is the method and motivation for eliminating the drain-to-source antiparallel diode in each of the high-side power MOSFETs.