US5815043A
Expired / Lapsed
US
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Frequency controlled ring oscillator having by passable stages
Assignee: Apple Inc
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Filing: 1997-02-13
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Granted: 1998-09-29
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Expires: 2017-02-13
Abstract
Abstract An improved ring oscillator in which frequency drift is controlled to provide reasonable accuracy is disclosed. The improved ring oscillator eliminates the frequency drift due processing variances. The ring oscillator provided by the invention incurs substantially less frequency drift than a conventional ring oscillator, but the frequency of the ring oscillator is still dependent on temperature and voltage changes. The improved ring oscillator according to the invention is particularly suited for operating as a localized oscillator that is used to facilitate periodic refreshing of DRAM within a computer.
Inventors
- 👤 Wing Hong Chow
- 👤 Robert L. Bailey
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 16:22
CPC Classifications
H; H03; H03L; H03L1/00; H03K; H03K3/00; H03K3/02; H03K3/027; H03K3/03; H03K3/0315; H03L7/00; H03L7/06; H03L7/08; H03L7/099; H03L7/0995; H03L7/0997; H03L7/16; H03L7/18; H03L7/181
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
84 words
A frequency controlled ring oscillator, comprising: a ring oscillator having a number of delay stages, said ring oscillator produces an output clock signal having an output frequency; a plurality of bypass switches, each of said bypass switches being coupled across one of the delay stages of said ring oscillator; and a controller for comparing the output frequency of the output clock signal with a reference frequency to produce a comparison result, and for opening or closing said bypass itches based on the comparison result.
Claim 2
Dependent Claim
84 words
A frequency controlled ring oscillator, comprising: a ring oscillator having a number of delay stages, said ring oscillator produces an output clock signal having an output frequency; a plurality of bypass switches, each of said bypass switches being coupled across one of the delay stages of said ring oscillator; and a controller for comparing the output frequency of the output clock signal with a reference frequency to produce a comparison result, and for opening or closing said bypass itches based on the comparison result.
Claim 3
Dependent Claim
28 words
The frequency controlled ring oscillator as recited in claim 1, wherein by opening or closing said bypass switches, the output frequency of the output clock signal is altered.
Claim 4
Dependent Claim
50 words
The frequency controlled ring oscillator as recited in claim 1, wherein when said controller determines that the output frequency of the output clock signal exceeds the reference frequency, said controller operates to control the opening of one or more of said bypass switches so as to decrease the output frequency.
Claim 5
Dependent Claim
52 words
The frequency controlled ring oscillator as recited in claim 3, wherein when said controller determines that the output frequency of the output clock signal is less than the reference frequency, said controller operates to control the closing of one or more of said bypass switches so as to increase the output frequency.
Claim 6
Dependent Claim
59 words
The frequency controlled ring oscillator as recited in claim 1, wherein when said controller determines that the output frequency of the output clock signal is less than the reference frequency by more than a first threshold amount, said controller operates to control the closing of one or more of said bypass switches so as to increase the output frequency.
Claim 7
Dependent Claim
56 words
The frequency controlled ring oscillator as recited in claim 5, wherein said controller determines that the output frequency of the output clock signal exceeds the reference frequency by more than a second threshold amount, said controller operates to control the opening of one or more of said bypass switches so as to decrease the output frequency.
Claim 8
Dependent Claim
66 words
The frequency controlled ring oscillator as recited in claim 1, wherein said controller comprises: a first counter to produce a first count value by counting in accordance with the reference frequency; a second counter to produce a second count value by counting in accordance with the output frequency; and logic for comparing the second count value against the first count value to produce the comparison result.
Claim 9
Dependent Claim
43 words
The frequency controlled ring oscillator as recited in claim 7, wherein said controller further comprises a switch control register, said switch control register couples to said bypass switches to effectuate the opening or closing of said bypass switches based on the comparison result.
Claim 10
Dependent Claim
54 words
The frequency controlled ring oscillator as recited in claim 7, wherein said first counter counts to the first count value which is a predetermined fixed count value of said first counter, and wherein said second counter counts until said first counter has reached the predetermined fixed count value thereby producing the second count value.
Claim 11
Dependent Claim
17 words
The frequency controlled ring oscillator as recited in claim 1, wherein said bypass switches are semiconductor switches.
Claim 12
Dependent Claim
22 words
The frequency controlled ring oscillator as recited in claim 1, wherein the delay stages of said ring oscillator are of different delays.
Claim 13
Dependent Claim
35 words
The frequency controlled ring oscillator as recited in claim 1, wherein each of the delay stages has a delay associated therewith that is essentially N unit delays, where N is an integer greater than 1.
Claim 14
Dependent Claim
56 words
The frequency controlled ring oscillator as recited in claim 12, wherein said ring oscillator has X delay stages, each of the X delay stages has a different delay, and wherein the X delay stages 1, 2, 3, . . . , X respectively have the N unit delays 1, 2, 6, . . . , N.
Claim 15
Dependent Claim
84 words
A frequency controlled ring oscillator, comprising: a ring oscillator having a number of delay stages, said ring oscillator produces an output clock signal having an output frequency; bypass means for bypassing one or more of the delay stages of said ring oscillator; and a controller operatively connected to said bypass means, said controller compares the output frequency of the output clock signal with a reference frequency to produce a comparison result, and controls the bypassing by said bypass means based on the comparison result.
Claim 16
Dependent Claim
84 words
A frequency controlled ring oscillator, comprising: a ring oscillator having a number of delay stages, said ring oscillator produces an output clock signal having an output frequency; bypass means for bypassing one or more of the delay stages of said ring oscillator; and a controller operatively connected to said bypass means, said controller compares the output frequency of the output clock signal with a reference frequency to produce a comparison result, and controls the bypassing by said bypass means based on the comparison result.
Claim 17
Dependent Claim
51 words
The frequency controlled ring oscillator as recited in claim 14, wherein when said controller determines that the output frequency of the output clock signal differs from the reference frequency, said controller operates to control the bypassing of one or more of the delay stages so as to adjust the output frequency.
Claim 18
Dependent Claim
52 words
The frequency controlled ring oscillator as recited in claim 14, wherein when said controller determines that the output frequency of the output clock signal is less than the reference frequency by more than a first threshold amount, said controller operates to control said bypass means so as to increase the output frequency.
Claim 19
Dependent Claim
50 words
The frequency controlled ring oscillator as recited in claim 16, wherein when said controller determines that the output frequency of the output clock signal exceeds the reference frequency by more than a second threshold amount, said controller operates to control said bypass means so as to decrease the output frequency.
Claim 20
Dependent Claim
66 words
The frequency controlled ring oscillator as recited in claim 14, wherein said controller comprises: a first counter to produce a first count value by counting in accordance with the reference frequency; a second counter to produce a second count value by counting in accordance with the output frequency; and logic for comparing the second count value against the first count value to produce the comparison result.
Claim 21
Dependent Claim
82 words
The frequency controlled ring oscillator as recited in claim 18, wherein said controller further comprises a switch control register, said switch control register couples to said bypass means to effectuate the bypassing based on the comparison result, and wherein said first counter counts to the first count value which is a predetermined fixed count value of said first counter, and wherein said second counter counts until said first counter has reached the predetermined fixed count value thereby producing the second count value.
Claim 22
Dependent Claim
22 words
The frequency controlled ring oscillator as recited in claim 14, wherein the delay stages of said ring oscillator are of different delays.
Claim 23
Dependent Claim
35 words
The frequency controlled ring oscillator as recited in claim 14, wherein each of the delay stages has a delay associated therewith that is essentially N unit delays, where N is an integer greater than 1.
Claim 24
Dependent Claim
56 words
The frequency controlled ring oscillator as recited in claim 21, wherein said ring oscillator has X delay stages, each of the X delay stages has a different delay, and wherein the X delay stages 1, 2, 3, . . . , X respectively have the N unit delays 1, 2, 6, . . . , N.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-09-28 | 2002-03-30 | 2002-09-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-09-28 | 2006-03-30 | 2006-09-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-09-28 | 2010-03-30 | 2010-09-29 | $7700.00 | Window Closed / Lapsed |