Texas Instruments Incorporated
LOW-IQ CURRENT MIRROR TRIMMING

Abstract:

A trimmable and switchable current mirror can be used in a bandgap voltage reference to calibrate the voltage reference without requiring access to measurement of the quiescent current I.sub.Q of the voltage reference. Trimmable transistors within the current mirror are alternately selectable as the diode-connected transistor via a mirror switch signal. A bandgap voltage difference is computed for two bandgap voltage values measured for alternate switched configurations of the current mirror. A set of such differences is computed and stored for different trim configurations of the mirror transistors, and the trim configuration corresponding to the lowest absolute value bandgap voltage difference can be selected as the optimal trim configuration. Following mirror transistor trim adjustment, a bandgap resistor trim can be adjusted to further calibrate the bandgap voltage reference.