Analog to digital converter with a differential output resistor-digital-to-analog-converter for improved noise reduction

An analog to digital converter circuit comprising:

• a. a comparator having a first and second input;
• b. a controller circuit having a successive-approximation register;
• c. first and second capacitor ladders having a plurality of capacitors connected in parallel, with one terminal of said first ladder connected to said first input of said comparator, and with one terminal of said second ladder connected to said second input of said comparator;
• and
• d. a voltage scaling circuit operable to scale the voltage on one plate of one capacitor connected to each of said capacitor ladders connected to said comparator further comprising:
• i. a resistor ladder having a plurality of serially connected resistors connected between two reference voltages;
• ii. a first set of switches operatively connected to allow said successive-approximation register to scale the voltage applied to said at least one capacitor connected to said first comparator input;
• and
• iii. a second set of switches operatively connected to scale the voltage applied to said at least one capacitor connected to said second comparator input.

A hard disk drive for a computer system comprising:

• a. a preamp for amplifying an analog signal detected by a disk head;
• b. An ADC converter for converting said analog signal to a digital signal comprising:
• 1. a comparator having a first and second input;
• controller circuit having a successive-approximation register;
• 2. first and second capacitor ladders having a plurality of capacitors connected in parallel, with one terminal of said first ladder connected to said first input of said comparator, and with one terminal of said second ladder connected to said second input of said comparator;
• and
• 3. a voltage scaling circuit operable to scale the voltage on one plate of one capacitor connected to each of said capacitor ladders connected to said comparator further comprising:
• i. a resistor ladder having a plurality of serially connected resistors connected between two reference voltages;
• ii. a first set of switches operatively connected to allow said successive-approximation register to scale the voltage applied to said at least one capacitor connected to said first comparator input;
• and
• iii. a second set of switches operatively connected to scale the voltage applied to said at least one capacitor connected to said second comparator input.