Multi-mode gain control loop for PRML class IV sampling data detection channel

摘要

A multi-mode gain control loop for a PR4, ML data channel, such as one included in a magnetic disk data storage device, includes an input for receiving from a source an analog signal stream including coded data to be detected; a VGA for amplifying the analog signal stream; an analog to digital converter for receiving the analog signal stream and for generating and putting out data samples therefrom; an analog gain control loop connected to generate an analog gain control from the analog data stream during a data non-read mode of the channel, to store the analog gain control in a storage circuit, and to apply the stored analog gain control constantly to control the VGA; and a digital gain control loop connected to generate gain vernier correction values from the data samples and for applying the gain vernier correction values through a gain DAC to provide an offset control to the VGA during a data read mode of the channel.