Abstract: Disclosed are a programmable digital device and method for generating tracking threshold signals for qualification of input peak signals in response to programmed digital gain signals which control the rate at which the envelope of the qualified input peak signals is followed, and in response to a programmed digital attenuation signal which determines the proportion of the peak envelope at which to generate new tracking threshold signals. The programmable digital device and method also provide a programmed clamp signal to clamp the positive and negative threshold signals to not fall below the programmed values. An anti-hang capability is provided to allow the thresholds to drop after a programmed time period during which no signal is detected. In an alternative arrangement, the centerline of the envelope is followed and used as the threshold.

Abstract: Disclosed are a programmable digital device and method for generating tracking threshold signals for qualification of input peak signals in response to programmed digital gain signals which control the rate at which the envelope of the qualified input peak signals is followed, and in response to a programmed digital attenuation signal which determines the proportion of the peak envelope at which to generate new tracking threshold signals. The programmable digital device and method also provide a programmed clamp signal to clamp the positive and negative threshold signals to not fall below the programmed values. An anti-hang capability is provided to allow the thresholds to drop after a programmed time period during which no signal is detected. In an alternative arrangement, the centerline of the envelope is followed and used as the threshold.

Abstract: In a pulse width modulated read signal channel for an optical disk drive, a data-transition threshold is maintained for data detection by a threshold tracking circuit that estimates the amplitude centerline data-transition threshold from the most recent maximum and minimum values of the read signal waveform. To improve the accuracy of the response of the centerline estimator, the threshold is increased or decreased based on the phase error at each read signal transition through the data-transition threshold. In addition, defects in the optical recording media are detected, and a defect present signal is used to inhibit the transition phase error input to the centerline estimator. This prevents the estimator from moving the threshold to an incorrect stable level. In addition, the defect present signal boosts the error feedback in the centerline estimator. The estimator then more quickly follows the read signal waveform.