US 6,281,652 B1 · Method of using two low-resolution DACS for converting high-resolution digital demands into analog output signals that monotonically drive an actuator motor in a disk drive

Abstract

Disclosed is a method in a disk drive that allows the functionality of a single high-resolution DAC to be replicated with a pair of lower-resolution DACs that are operated in a unique manner that provides monotonic behavior and reduces both differential and integral non-linearity. The two lower-resolution DACs take up substantially less space that one higher-resolution DAC when implemented in a semiconductor die. The method combines coarse values from one DAC with fine values from the other DAC to form a combined analog output signal within operational segments that collectively span a range of N-bit demands. The method operates such the operational segments overlap one another by 50 percent, with an endpoint of each operational segment ending near a center of an overlapped operational segment. The method's overlapping relationship tends to cause the combined analog output voltage to vary monotonically, by maintaining the X-bit command and only varying the Y-bit command whenever possible for small changes in the combined analog output signal.

Claims34

Dependent claims

A method of converting a sequence of N-bit demands into analog output signals that drive an actuator motor in a magnetic disk drive using two lower-resolution digital-to-analog converters (DACS) including a first DAC of at least X-bits of resolution that produces a coarse output signal (where X<N) and a second DAC of at least Y-bits of resolution that produces a fine output signal (where Y<N), the method comprising the steps of:

receiving (100) a new N-bit demand derived from a range of N-bit demand values;
converting (120) the new N-bit demand into an X-bit command and a Y-bit command by:
selecting (112) the X-bit command corresponding to a prior N-bit demand if the new N-bit demand is near enough to the prior N-bit demand such that the new N-bit demand may be attained by re-using the X-bit command which corresponds to the prior N-bit demand and varying the Y-bit command (111, or 11a & 11b);
else selecting (113) a new X-bit command, and
subtracting (114) the selected X-bit command from the new N-bit demand to calculate a new Y-bit command;
producing a coarse output signal with the first DAC based on the selected X-bit command;
producing a fine output signal with the second DAC based on the calculated Y-bit command;
and
combining (140) the coarse and fine output signals to produce the analog output signal that drives the actuator motor.

6 more elements

A method of converting a sequence of N-bit demands into analog output signals that drive an actuator motor in a magnetic disk drive using two lower-resolution digital-to-analog converters (DACs) including a first DAC of at least X-bits of resolution that produces a coarse output signal (where X<N) and a second DAC of at least Y-bits of resolution that produces a fine output signal (where Y<N), the method comprising the steps of:

(a) receiving (100) a new N-bit demand derived from a range of N-bit demand values;
(b) converting (120) the new N-bit demand into an X-bit command and a Y-bit command wherein X is equal to N−Y+1 such that there are 2N−Y+1 possible X-bit commands and 2N−Y+1 operational segments that are each defined by a locus of commands corresponding to one of the 2N−Y+1 possible X-bit commands and a set of 2Y Y-bit commands, the converting step including the sub-steps of:
(i) selecting (112) the X-bit command corresponding to a prior N-bit demand if the new N-bit demand is near enough to the prior N-bit demand such that the new N-bit demand may be attained by re-using the X-bit command that corresponds to the prior N-bit demand and varying the Y-bit command (111, or 11a & 11b);
else selecting (113) a new X-bit command, and
(ii) subtracting (114) the selected X-bit command from the new N-bit demand to calculate a Y-bit command;
(c) producing (120) a coarse output signal with the first DAC based on the selected X-bit command;
(d) producing (120) a fine output signal with the second DAC based on the calculated Y-bit command;
(e) scaling (included in 140) the coarse and fine output signals into first and second scaled output signals by using first and second scaling factors that are provided in a ratio of 1:2N−Y so that the 2N−Y+1 operational segments collectively span the range of N-bit demand values by successively overlapping one another by 50 percent, with an endpoint of each operational segment ending near a center of an overlapped operational segment;
and
(f) summing (included in 140) the first and second scaled output signals together to produce the analog output signal that drives the actuator motor.

7 more elements

Dependencies are inferred from the claim text.

Method of using two low-resolution DACS for converting high-resolution digital demands into analog output signals that monotonically drive an actuator motor in a disk drive

Life of this patent

Method of using two low-resolution DACS for converting high-resolution digital demands into analog output signals that monotonically drive an actuator motor in a disk drive

Life of this patent

Abstract

Claims34