Samsung spinpoint v40, 3.5" hard disk drives manual Time Base Generator, Automatic Gain Control

DISK DRIVE OPERATION

The read/write channel functions include a time base generator, AGC circuitry, asymmetry correction circuitry (ASC), analog anti-aliasing low-pass filter, analog to digital converter (ADC), digital FIR filter, timing recovery circuits, Viterbi detector, sync mark detection, 32/34 rate block code ENDEC, serializer and de-serializer, and write pre-compensation circuits. Servo functions include servo data detection and PES demodulation. Additionally the 88C5200 contains specialized circuitry to perform various parametric measurements on the processed read signal. This allows for implementation of self-tuning and optimization capability in every drive built using the 88C5200.

A 9-bit NRZ interface is provided to support high speed data transfers to and from the controller. Programming of the 88C5200 is performed through a serial interface. The serial interface is also used to read various channel parameters that are computed on the fly.

5.2.3.1Time Base Generator

The time base generator provides the write frequency and serves as a reference clock to the synchronizer during non-read mode.

5.2.3.2Automatic Gain Control

The AGC accepts a differential signal from the pre-amp, and provide a constant output amplitude to the analog filter. It’s capable of accepting signal ranges from 40 mV to 400 mVppd.

5.2.3.3Asymmetry Correction Circuitry (ASC)

The ASC circuit is designed to correct for amplitude asymmetry introduced by MR heads. The compensation range of this circuit is +/-45%. This circuit allows optimal bias current to be used independent of the asymmetry effect.

5.2.3.4Analog Anti-Aliasing Low Pass Filter

The 7th order equal-ripple analog filter provide filtering of the analog signal from AGC before it’s being converted to digital signal with the ADC. It’s main function is to avoid aliasing for the ADC circuit.

5.2.3.5Analog to Digital Converter (ADC) and FIR

The output of the analog filter is quantified using a 6 bit FLASH ADC. The digitized data is then equalized by the FIR to the NPV target response for Viterbi detection. The FIR filter consists of 7 independent programmable taps.

32 SpinPoint V40 Product Manual