Fine phase frequency multipiler for a brushless motor and corresponding control method

In a motor controller, a circuit for generating a fine rotor position signal comprising:

• a circuit input terminal structured to receive a coarse rotor position signal;
• a countdown timer circuit having a load terminal coupled to the circuit input terminal, the countdown timer circuit also having a data value terminal, and an output terminal;
• and
• a loading circuit coupled to the data value terminal, the loading circuit structured to load a pre-set value into the countdown timer.

A hard disk drive, comprising:

• a plurality of disk platters having a substrate surface capable of storing information;
• a plurality of data heads, at least one data head positioned near the substrate surface of each of the disk platters;
• a spindle coupled to the plurality of disk platters such that when the spindle is rotated, so are the plurality of disk platters;
• a disk drive motor coupled to the spindle and structured to rotate the spindle;
• and
• a disk drive motor controller circuit coupled to the disk drive motor and including a sub-circuit for generating a fine rotor position signal, the sub-circuit including:
• a circuit input terminal structured to receive a coarse rotor position signal,
• a first counter circuit coupled to the circuit input terminal and having a first counter output, the first counter circuit structured to count at a first rate,
• a second counter circuit having a second counter output and structured to count at a second rate, and
• a comparator structured to receive the outputs of the first and second counter circuits at a first and second input, respectively, the comparator structured to output the fine rotor position signal after comparing signals received at its first and second inputs.

A method of generating a fine rotor positional signal in a DC motor comprising:

• accepting a first and a second received rotor positional signal from a circuit controlling the DC motor;
• counting with a first counter at a first rate to a first data value representing a time period between the first and second received rotor positional signals;
• counting with a second counter with a second rate from an original data value toward a second data value;
• and
• generating the fine rotor positional signal when the second counter reaches the second data value.