Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
1998-02-06
2001-09-04
Smith, Matthew (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000, C716S030000, C327S054000, C700S075000
Reexamination Certificate
active
06286127
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention pertains in general to control circuits and, more particularly, to a control circuit that is programmable for multiple functions at a single terminal.
BACKGROUND OF THE INVENTION
Integrated circuit controllers are widely used in power management applications such as regulated power supplies, battery chargers and the like. The general trend has been to design such circuits to accomplish more of the control functions required in a wider variety of applications to reduce component count and design time, or to provide greater versatility. Product designers are often faced with tradeoffs of desired features with cost objectives.
One problem heretofore unmet in a battery charger application, for example, is providing for control of the timing of a plurality of battery charging modes including fast charge, trickle charge and topoff charge. Various types of battery chemistry and discharge history require different timing of each of these modes to tailor the battery charging operation to a particular type of battery. Typically, several external time references connected to several IC pins may be required to accomplish the desired result.
Another problem found in the exemplary battery charger or other power supply regulator applications is providing a controller that is responsive to both polarities of the load current feedback signal without duplicating sensing circuitry. Typically, this requirement is met by separate amplifiers and references for each polarity which add cost to the system. Further, moving the sense resistor from one lead of the battery to be charged to the other lead ordinarily requires a different circuit design. Alternatively, changing the terminal in the circuit where system ground and chip ground are tied together may also require different circuitry. It would be useful to provide a single controller design with several options for locating the current sense resistor or referencing the chip control circuit ground in a variety of applications.
Thus, several primary objectives of circuit designers are to provide maximum functionality in a circuit controller without requiring a large number of terminals to interface with input and output components. These goals are typically met in an integrated circuit, for example, by limiting the number of required external components to those that are virtually impossible to fabricate on an integrated circuit. Heretofore, these objectives have been difficult to achieve while accommodating different types of battery charger or regulator circuits.
SUMMARY OF THE INVENTION
The present invention disclosed and claimed herein comprises a control circuit that can be configured to provide a plurality of charging modes by connecting one set of program elements to a single programming terminal. A programmable circuit is provided within the circuit which generates a timing signal for a first charging mode determined by a pair of selected program elements. The programmable circuit is also operable to generate a second timing signal for a second charging mode determined by one of the selected program elements in combination with another element internal to the control circuit. In both first and second modes, the values of the program elements, selectable by the user, determine the frequencies of the respective generated signals. A voltage provided internally forces a condition at the programmable pin to control the second charging mode. Further, control of a third charging mode may be effected from a comparison, performed within the control circuit, of the timing signals generated for the first and second charging modes. Thus, three charging modes are controlled by two passive components or program elements connected to a single programmable terminal associated with the control circuit.
In another aspect of the invention, each of the program elements may be resistive or reactive, capacitive or inductive, and may be selected by the user and varied continuously depending on the particular application. In similar fashion, this concept may be generalized to provide for setting or programming other sets of multiple parameters or operating modes in other control applications, particularly where timing or voltage level references are set by external components connected to a programming pin.
In a further aspect of the invention a circuit responsive to either positive or negative input sensing at a single sense terminal is provided. A differential comparator within the control circuit is constructed of a single amplifier that is operable without modification with an input sense signal which swings high or low, i.e., in a positive or negative direction. The output of this comparator is coupled to a wired OR circuit which provides an output control signal responsive to the absolute value of the input signal whenever it exceeds a systematic offset internal to the comparator. The systematic offset inherently provides the switching point for both input signal polarities. The comparator thus needs no external reference to set the switching point; it is preset in the comparator. The comparator may also include a temperature compensating bias generator for maintaining circuit stability and assuring a constant systematic offset despite operating temperature variations or manufacturing process variations.
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Fischer Mark Charles
King Ken Richard
Brady W. James
Smith Matthew
Swayze, Jr. W. Daniel
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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