A 20 Mhz BiCMOS peak detect pulse qualifier and area detect servo demodulator for hard disk drive servo loop

With concentric data tracks separated radially by less than 10/spl mu/m, accurately detecting servo information on a magnetic disk is a crucial function of magnetic storage read channels. Valid servo Gray code confirms that the read/write head is in the servo sector. Servo bursts with different offsets from track centers provide vital track positioning information for the read/write head. The servo Gray code is a series of positive and negative pulses. The pulse qualifier outputs a RDS pulse for each pulse whose amplitude exceeds a user programmed threshold. Following the servo Gray code, the servo demodulator integrates over each servo burst, and outputs the magnitude of each integration. Trade-offs between power, area, and sensitivity to noise are considered in the servo demodulator architecture design. This implementation of a peak-detect pulse qualifier and an area detect servo demodulator is fabricated in 5V 0.8/spl mu/m BiCMOS. Total area of the two blocks is 2.15mm/sup 2/, and total power consumption of the two blocks is 130mW.