National Semiconductor Corporation

Siew Siong Teo

Michael Eugene Broach

Luan Minh Vu

Gary A Brown

Richard Frank

An apparatus and method provide for curvature corrected temperature variations in a band-gap reference circuit. The apparatus includes a band-gap cell, an IPTAT circuit, a resistor, and a feedback circuit. The band-gap cell is arranged to provide a band-gap voltage. The resistor circuit is coupled to both the band-gap cell and the IPTAT circuit. The feedback circuit is arranged to selectively activate the IPTAT circuit such that an additional correction factor is added to the temperature response of the band-gap cell to provide a second order curve. The IPTAT circuit can be implemented as a simple transistor that is responsive to changes in absolute temperature.

Curvature corrected bandgap circuit

A polysilicon fuse trim read cell utilizes a fuse structure in a single bit memory cell. When the fuse structure is blown, the memory cell can be read and its stored value retained as a digital output. The cell uses no power in the steady state.

Polyfuse trim read cell

An integrated circuit system and method provides a reliable low voltage reference including undervoltage lockout capabilities that prevent a premature or false response. A physical constant trigger circuit initiates a response based upon a physical constant (e.g. a stable point associated with a voltage summation in a transistor circuit with components configured to produce equal and opposite temperature coefficients). A response includes changing polarities of the transistor circuit at a predetermined inflection point. A comparator compares signals from the physical constant trigger circuit and determines when a change occurs in the response. A voltage divider provides a varying voltage to the physical constant trigger and when the voltage level corresponds to the physical constant it is utilized as the reference voltage. An input signal port conveys an input signal to the voltage divider and output port conveys an indication of the response (e.g., a desired reference voltage is available).

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Siew Siong Teo