A voltage reference with on-chip trimmable temperature coefficient and offset voltage

This paper demonstrates a circuit for compensation of the temperature errors in voltage references, that not only is able to compensate first order changes of the temperature coefficient, but can also correct for the offset error that is unavoidable in production due to variations in process conditions and mismatches. The temperature compensation is programmable via three control bits, the remaining offset error is compensated by eight control bits and an external provided reference voltage. The compensation procedure can be controlled by a internal digital block or via external signals. The actual calibration data can then be saved in several possible ways (EPROM, laser fuses, external Memory, ...). Extensive simulations show that the proposed circuit is able to reduce the average temperature error by more than 40% and the overall absolute error by more than 90 % of the uncalibrated reference voltage.