Data and servo sampling in synchronous data detection channel

An improved analog-to-digital converter circuit for a sampling data detection channel of a disk drive, the improved analog-to-digital converter circuit comprising:

• a first analog summing circuit for receiving an analog signal from a first source, the first analog summing circuit receiving an analog dithering signal from a second source, wherein the first analog summing circuit sums the analog signal and the analog dithering signal to provide a first summed analog signal;
• second and third analog summing circuits connected to the first summing circuit, the second analog summing circuit for adding a first predetermined offset value to the first summed analog signal to provide a second analog sum, the third analog summing circuit for adding a second predetermined offset value to the first summed analog signal to provide a third analog sum;
• a first analog-to-digital converter connected to the second summing circuit and analog front end circuit for transforming the second analog sum to a sequence of first digitized samples;
• a second analog-to-digital converter connected to the third summing circuit and analog front end circuit for transforming the third sum to a sequence of second digitized samples;
• and
• a digital summing and averaging circuit for summing and averaging the first and the second digitized samples to provide a digitized output.

An improved analog-to-digital converter circuit for a partial-response, maximum likelihood synchronous sampling data detection channel of a hard disk drive, the hard disk drive including a rotating rigid disk having data track areas divided by spoke areas, the improved analog-to-digital converter circuit for synchronously sampling user data in the data track areas at a first quantization resolution and for synchronously sampling a servo burst field from at least one of the spoke areas at a second quantization resolution effectively greater than said first quantization resolution and comprising:

• an input for receiving an analog signal to be quantized from an analog read data channel of the disk drive;
• a source providing an analog dither signal,
• a first summing circuit for summing the analog signal with the analog digital values to produce a first sum at an output,
• a first path connected to the output and including a second summing circuit and a first analog-to-digital converter for generating first digital samples at the first quantization resolution, the second summing circuit for combining the first sum with a first predetermined offset value,
• a second path connected to the output and including a third summing circuit and a second analog-to-digital converter for generating second digital samples at the first quantization resolution, the third summing circuit for combining the first sum with a second predetermined offset value different from said first predetermined offset value, and
• digital averaging means connected to average the first and second digital samples over a predetermined averaging interval to provide average samples having the second quantization resolution.