Design and operation of a fully integrated BiC/DMOS head-actuator PIC for computer hard-disk drives

A fully integrated head-actuator power integrated circuit (PIC) for computer hard-disk drives is described including a 1-A, 10-W CMOS H-bridge class-B amplifier. Operation of the complementary MOS-transistor power output stage includes a small-signal on-track mode and a five-interval high-speed large-signal seek mode. Analysis of a seek event reveals that maximum power dissipation occurs during the acceleration and deceleration intervals. Inductive flyback during break-before-make operation is clamped by integral multicollector bipolar transistors as confirmed by measurements and PISCES simulations. The mechanisms, occurrence, and device design considerations of the output transistor's flyback current partitioning into type A (source) and type B (N/sub well/) collector and base (body) current components are analyzed. The concept and implementation of a synchronous clamp are introduced. Finally, performance and parasitic suppression considerations of an advanced self-isolated BiC/DMOS process and device arsenal are discussed.<
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