Programmable low drift reference voltage generator
AssigneeExar Corporation
InventorRoger Levinson
Life of this patent
Estimating the term…
Abstract
A reference voltage generating method and circuit is disclosed where the output can be programmably calibrated for minimum temperature drift. Output calibration is performed by adjusting a value of resistance of a resistor in a band-gap circuit. Digitally programmable switches are used to incrementally reduce or increase the value of the target resistor. The control circuit according to the present invention is also designed such that it tracks variations in process and temperature.
Claims17
A reference voltage generating circuit comprising:
- a band-gap circuit having a first resistor, a second resistor and a third resistor coupled to inputs of an amplifier, said amplifier having an output generating a reference voltage, said first resistor being divided into a plurality of serially coupled resistor segments;
- a corresponding plurality of programmable switches respectively coupled in parallel to said plurality of resistor segments;
- and
- a control circuit coupled to said plurality of programmable switches for controlling a state of said switches,
- wherein, by turning selected ones of said plurality of switches on or off, a resistance value of said first resistor element is adjusted thereby fine tuning a value of said reference voltage.
A band-gap reference voltage generating circuit comprising:
- a band-gap reference circuit having a first band-gap resistor divided into a plurality of serially coupled resistor segments;
- a plurality of field effect transistors (FETs) each having first and second source/drain terminals respectively coupled across one of said plurality of serially coupled resistor segments;
- and
- a digitally programmable control circuit having output terminals coupled to gate terminals of said plurality of FETs,
- wherein, said output terminals of said digitally programmable control circuit adjust a value of resistance of said first band-gap resistor by controlling a state of said plurality of FETs.
A method for generating a band-gap reference voltage comprising the steps of:
- dividing a resistor in the band-gap circuit into a plurality of serially coupled segments of resistors;
- coupling in parallel to each of said plurality of serially coupled segments of resistors, a field effect transistor;
- and
- adjusting a resistance value of said resistor by controlling a state of said field effect transistor.
Dependencies are inferred from the claim text.