Low voltage charge pump for use in a phase locked loop

Details Low voltage charge pump for use in a phase locked loop Low voltage charge pump for use in a phase locked loop

2001-05-25

2003-01-28

Callahan, Timothy P. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Synchronizing

C327S148000

Reexamination Certificate

active

06512404

ABSTRACT:

BACKGROUND
Computer hard disk drives, also known as fixed disk drives or hard drives, have become a de facto data storage standard for computer systems and are making inroads into consumer electronics as well. Their proliferation can be directly attributed to their low cost, high storage capacity and reliability, in addition to wide availability, low power consumption, fast data transfer speeds and decreasing physical size.
Disk drives typically consist of one or more rotating magnetic platters encased within an environmentally controlled housing. The disk drive further includes electronics and mechanics for reading and writing data and interfacing with other devices. Read/write heads are positioned in proximity of the platters, typically towards each face, to record and read data. The hard drive electronics are coupled with the read/write heads and include numerous components to control the position of the heads and generate or sense the electromagnetic fields representing data. The electronics encode data received from a host device, such as a personal computer, and translate the data into magnetic encodings, which are written onto the disk platters. When the host device requests data, the electronics locate the desired data on the platters, sense the magnetic encodings that represent that data, and translate the encodings into the binary digital information. Error detection and correction algorithms may also be applied to ensure accurate storage and retrieval of data.
Advancements in the read/write head and the methods of interpreting magnetic encodings have been made. A traditional hard drive has several read/write heads that interface with the several magnetic platters and the hard drive electronics. The read/write heads detect and record the encoded data as areas of magnetic flux. Data bits, consisting of binary 1's and 0's, are encoded by the presence or absence of flux reversals. A flux reversal is a change in the magnetic flux in two contiguous areas of the disk platter. Data is read using method as “Peak Detection” by which a voltage peak imparted in the read/write head is detected when a flux reversal passes the read/write head. However, increasing storage densities, which require reduced peak amplitudes, better signal discrimination and higher platter rotational speeds, are pushing the peaks in closer proximity. Thus, peak detection methods are becoming increasingly complex.
Magneto-resistive (“MR”) read/write heads have been developed. MR read/write heads have increased sensitivity to sense smaller amplitude magnetic signals and provide increased signal discrimination, addressing some of the problems with increasing storage densities. In addition, technology known as Partial Response Maximum Likelihood (“PRML”) has been developed to further address the desire to provide increased data storage densities. PRML is an algorithm implemented in the disk drive electronics to interpret the magnetic signals sensed by the read/write heads. PRML based disk drives read the analog waveforms generated by the magnetic flux reversals stored on the disk. Instead of looking for peak values, PRML based drives digitally sample this analog waveform (the “Partial Response”) and use advanced signal processing technologies to determine the bit pattern represented by that wave form (the “Maximum Likelihood”). This technology, combined with MR heads, have permitted further increases in data storage densities. PRML technology tolerates more noise in the magnetic signals, permitting use of lower quality platters and read/write heads, which also increases manufacturing yields and lowers costs.
With many different drives available from multiple manufacturers, hard drives are typically differentiated by factors such as cost/megabyte of storage, data transfer rate, power requirements and form factor (physical dimensions) with the bulk of competition based on cost. With most competition between hard drive manufacturers coming in the area of cost, there is a need for enhanced hard drive components which prove cost effective in increasing supplies and driving down manufacturing costs all while increasing storage capacity, operating speed, reliability and power efficiency.
SUMMARY
The embodiments described below to a low voltage charge pump for a phase locked loop (“PLL”) in a partial response, maximum likelihood (“PRML”) based read/write channel for a hard disk drive. The charge pump is operative to provide linear control of a potential at a loop filter node of the PLL. The charge pump includes a linear pull-up circuit operative to selectively increase the potential at the loop filter node. The charge pump further includes a linear pull-down circuit operative to selectively decrease the potential at the loop filter node. The pull-up circuit is operative to linearly increase the potential to a voltage within 150 mV of a most positive supply voltage of the pull-up circuit, and the pull-down circuit is operative to linearly decrease the potential to voltage within 150 mV of a least positive supply voltage of the pull-up circuit. The pull-up circuit and the pull-down circuit are configured to provide a substantially constant current at the loop filter input node independent of the loop filter node voltage.
The preferred embodiments further relate to a method for charging a loop filter. The method includes the acts of selectively increasing a potential for a loop filter node by providing positive constant current to the loop filter node; and selectively decreasing a potential for the loop filter node by drawing a negative constant current from the loop filter input node. The act of increasing the potential includes using a positive constant current source configured to provide current to the loop filter input node, wherein the loop filter node potential is linearly increased to within 150 mV of a most positive power supply voltage for the constant current source. The act of decreasing the potential includes using a negative constant current source configured to draw substantially constant current from the loop filter input node, wherein the loop filter node potential is linearly decreased to within 150 mV of a least positive power supply voltage for the constant current source.
The foregoing discussion of the summary of the invention is provided only by way of introduction. Nothing in this section should be taken as a limitation on the claims, which define the scope of the invention. Additional objects and advantages of the present invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the present invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the claims.


REFERENCES:
patent: 5963025 (1999-10-01), Colli
patent: 6107889 (2000-08-01), Strange et al.
patent: 6160432 (2000-12-01), Rhee et al.
patent: 6229361 (2001-05-01), Henwood
patent: 6278332 (2001-08-01), Nelson et al.
patent: 6326852 (2001-12-01), Wakayama
patent: 6332004 (2001-12-01), Chan
“Synchronous Recording Channels—PRML & Beyond”, rev. 5.61 14.E.18, 1999, published by Knowledge Tek, Inc., Broomfield, Colorado.
“PRML: Seagate Uses Space Age Technology” available on the Internet at http://www.seagate.com/support/kb/disc/prml.html, 2 pages, last accessed Apr. 9, 2001.
“Technologies—PRML” available on the internet at http://www.idema.org/about/industry/ind_tech_prml.html, 1 page, last accessed Apr. 9, 2001.
“Reference Guide —Hard Disk Drives” available on the Internet at http://www.storagereview.com/guide2000/ref/hdd, 13 pages, last accessed Apr. 9, 2001.
“MR and PRML: Technologies in Synergy” available at on the Internet at http://www.lionsgate.com/Home/Baden/public_html_index/SCSI/Quantum_White_Pape rs/MR_Head/MR, 4 pages, last accessed Apr. 9, 2001.
“A Tutorial on Convolutional Coding with Viterbi Decoding” available on the Internet at http://pw1.netcom.con/<chip.f/viterbi/tutorial.html, 10 pages, last accessed Apr. 9, 200

Affiliated with

Also associated with

Rating

Low voltage charge pump for use in a phase locked loop does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Low voltage charge pump for use in a phase locked loop, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low voltage charge pump for use in a phase locked loop will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3009214