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_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