US5089793A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Semiconductor device having an oscillatory circuit
Assignee: Seiko Epson Corp
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Filing: 1990-09-24
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Granted: 1992-02-18
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Expires: 2010-09-24
Abstract
Abstract Disclosed is a semiconductor device in which a CPU and an oscillation circuit are driven with the same driving voltage. The oscillation circuit is constituted by a plurality of oscillation invertors having different characteristics respectively corresponding to different reference voltages for driving the CPU. One of the oscillation invertors is selected corresponding to the driving voltage of the CPU so that the oscillation signal of the selected oscillation circuit is sent out as a system clock. It is therefore possible to obtain preferable characteristics that, when the driving voltage of the CPU is changed over in accordance with a program, fluctuation in the driving ability of the oscillation invertors, which has been conventionally generated, is prevented from occurring, so that oscillation easily starts upon turning-on of a power supply, oscillation hardly stops when a source voltage becomes low, and high harmonics oscillation hardly occurs.
Inventors
- 👤 Hidenori Nagao
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 18:40
CPC Classifications
H; H03; H03L; H03L1/00; G; G06; G06F; G06F1/00; G06F1/04; G06F1/08; G06F1/26
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
167 words
A semiconductor device comprising: a plurality of reference voltage generating circuits for generating reference voltages different from each other; a selection control storage circuit for storing a selection signal for selecting one of said reference voltage generating circuits in accordance with a command from a CPU; a plurality of analog switches provided respectively corresponding to said reference voltage generating circuits, each of said analog switches being arranged so as to open on the basis of said selection signal supplied thereto to thereby send out the reference voltage from said corresponding reference voltage generating circuit; and an oscillation circuit constituted by a plurality of oscillation invertors provided respectively corresponding to said reference voltage generating circuits, said oscillation invertors being provided with said reference voltages supplied through said analog switches as driving voltages, said oscillation invertors being selected on the basis of said selection signal supplied thereto so that an oscillation signal of the selected one of said oscillation invertors is supplied to a microcomputer as a system clock.
Claim 2
Dependent Claim
167 words
A semiconductor device comprising: a plurality of reference voltage generating circuits for generating reference voltages different from each other; a selection control storage circuit for storing a selection signal for selecting one of said reference voltage generating circuits in accordance with a command from a CPU; a plurality of analog switches provided respectively corresponding to said reference voltage generating circuits, each of said analog switches being arranged so as to open on the basis of said selection signal supplied thereto to thereby send out the reference voltage from said corresponding reference voltage generating circuit; and an oscillation circuit constituted by a plurality of oscillation invertors provided respectively corresponding to said reference voltage generating circuits, said oscillation invertors being provided with said reference voltages supplied through said analog switches as driving voltages, said oscillation invertors being selected on the basis of said selection signal supplied thereto so that an oscillation signal of the selected one of said oscillation invertors is supplied to a microcomputer as a system clock.
Claim 3
Dependent Claim
63 words
A semiconductor device according to claim 1, in which said oscillation inverters are different in driving ability from each other, the driving voltages supplied to said oscillation inverters being different from each other so that the higher the driving ability of the oscillation inverter the lower the driving voltage supplied thereto, said oscillation inverters being the same in oscillation frequency with each other.
Claim 4
Dependent Claim
80 words
A semiconductor device according to claim 1, in which said oscillation circuit are a pair of oscillation, inverters one of said oscillation inverters having a high driving ability and being supplied with a low driving voltage from one of said analog switches, the other of said oscillation inverters having a low driving ability and being supplied with a high driving voltage from the other of said analog switches, said oscillation inverters being the same in oscillation frequency with each other.
Claim 5
Dependent Claim
49 words
A semiconductor device according to claim 3, in which said oscillation circuit is a low frequency oscillation circuit and said semiconductor device further comprises an operational amplifier for stabilizing said reference voltage sent from said analog switch and for supplying said stabilized voltage to said low frequency oscillation circuit.
Claim 6
Dependent Claim
88 words
A semiconductor device according to claim 4, in which said microcomputer includes said CPU for executing an operational function and for controlling the operation of said computer, a data bus connected to said CPU for making delivery of data, an address bus connected to said CPU, an ROM connected to said data bus and said address bus and having a program stored therein for determining the operation of said computer, and an RAM connected to said data bus and said address bus for storing data for operational processing.
Claim 7
Dependent Claim
151 words
A semiconductor device according to claim 5, further comprising: a high frequency oscillation circuit supplied with said reference voltage, as a driving voltage, through said operational amplifier; a high frequency oscillation control circuit for controlling drive of said high frequency oscillation circuit on the basis of a command from said CPU; a clock change-over control circuit for producing a change-over control signal for selecting one of an output of said low frequency oscillation circuit and an output of said high frequency oscillation circuit on the basis of a command from said CPU; and a clock synchronization circuit for selecting one of the output of said low frequency oscillation circuit and the output of said high frequency oscillation circuit in response to said change-over control signal from said clock change-over control circuit, and for synchronizing the selected output so as to supply the synchronized output, as a system clock, to said computer.
Claim 8
Dependent Claim
75 words
A semiconductor device according to claim 6, further comprising a reset signal line connected to said CPU of said microcomputer, said selection control storage circuit, said high frequency oscillation control circuit, and said clock change-over control circuit so as to initialize said CPU, said selection control storage circuit, said high frequency oscillation control circuit, and said clock change-over control circuit at the time of turning-on of a power supply or initialization of said semiconductor device.
References Cited (Backward Citations)
JPS61168709A
Cited
US4882738A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-02-17 | 1995-08-19 | 1996-02-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-02-17 | 1999-08-19 | 2000-02-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-02-17 | 2003-08-19 | 2004-02-18 | $7700.00 | Window Closed / Lapsed |