Electrical transmission or interconnection systems – Plural supply circuits or sources – Substitute or emergency source
Patent
1983-12-09
1984-05-29
Goldberg, E. A.
Electrical transmission or interconnection systems
Plural supply circuits or sources
Substitute or emergency source
365229, 371 66, H02J 906
Patent
active
044517424
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention pertains to the supplying of power to an integrated circuit and more particularly to the supplying of backup power from batteries to an integrated circuit.
BACKGROUND OF THE INVENTION
In the application for semiconductor memories there are requirements for nonvolatile data storage, that is, retaining stored information despite loss of the supply voltage. Current methods for achievening nonvolatile storage include erasable and electronically alterable read only memories, bubble memories and CMOS memories with an external battery. Each of the present approaches has distinct drawbacks. The erasable read only memories require high voltages, have slow writing and in some cases have a block erase. Further the erasable memories require exposure to ultraviolet light for 10-30 minutes. The electronically alterable memories have a limited number of writes cycles and therefore a limited lifetime. The bubble memories have relatively slow read and write cycles and at present are quite expensive. The use of an external battery to back up a CMOS memory requires additional mounting space, added circuitry and extra expense.
In view of the above problems with nonvolatile storage there exists a need for a control circuit for providing primary and battery power to a semiconductor circuit, especially memory circuits.
SUMMARY OF THE INVENTION
A selected embodiment of the present invention comprises a method for providing power to an integrated circuit from one of a plurality of sources. In a first step the voltages of first and second backup power sources are compared to select the one having the higher voltage. The backup power source having the higher voltage is connected to supply power to the integrated circuit. The voltages of a primary power source and the backup power source having the higher voltage are compared. The primary power source is connected to supply power to the integrated circuit when the voltage of the primary power source exceeds the voltage of the backup power source having the higher voltage by a preset threshold. In a further aspect of the present invention the control signal inputs to the integrated circuit are disabled when the voltage of the primary power source becomes less than that of a predetermined voltage.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken into conjunction with the accompanying drawings in which:
FIG. 1 is a block diagram of the power control circuit of the present invention;
FIG. 2 is a chart illustrating the operation of the circuit shown in FIG. 1 as a function of the supply voltage V.sub.cc ;
FIG. 3 is a schematic illustration of the VCCOK circuit shown in FIG. 1;
FIG. 4 is an illustration of various wave forms which are generated by the circuit shown in FIG. 3;
FIG. 5 is a schematic illustration of the BATTSWITCH circuit shown in FIG. 1;
FIG. 6 is a schematic illustration of a portion of the CONTROL LOGIC circuit shown in FIG. 1;
FIG. 7 is a schematic illustration of additional circuitry for the CONTROL LOGIC circuit shown in FIG. 1;
FIG. 8 is a schematic illustration of the analogue switches and a portion of the voltage reference circuit shown in FIG. 1;
FIG. 9 is a schematic illustration of further circuitry for the VOLTAGE REF circuit shown in FIG. 1; and
FIG. 10 is a schematic illustration of further circuitry for the VOLTAGE REF circuit shown in FIG. 1.
DETAILED DESCRIPTION
The circuit of the present invention is illustrated in block diagram form in FIG. 1. Circuit 20 serves to provide power to an integrated circuit (not shown). The power can be provided from any one of three sources. The first source is the conventional primary power supplied through a circuit board to a pin of the integrated circuit. This is referred to as primary V.sub.cc and is received at a terminal 22. A second source of power is a first battery which is connected to a terminal 24. A third source of power is a second bat
REFERENCES:
patent: 3555290 (1971-01-01), Ellermeyer
patent: 3573483 (1971-04-01), White
patent: 3859638 (1975-01-01), Hume
patent: 4143283 (1979-03-01), Grof et al.
Bodner, R. E. I.B.M. Technical Disclosure Bulletin "Fault Indication for Multiple Power Supplies," vol. 17, No. 1, Jun. 1974, pp. 175-177.
Rayner, D. New Electronics, "Battery Back-Up Voltage Monitor," vol. 13, No. 19, Sep. 30, 1980, p. 38.
Deboer Todd E.
Goldberg E. A.
Mostek Corporation
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