DESCRIPTIONInitial Output Voltage at 25 CPREFERRED UNIT(S)V, %V MAX VINTotal Temperature RangeTemperatureCoefficientLong-TermStabilityNoiseChange in Output vs TimeMeasured Over 1000 Hours or More0.1Hz to 10Hzppm/ Cppm kh10Hz to 1kHz VP-P, ppmP-P V RMS , ppm RMSTable 1. Reference Accuracy SpecificationsTight initial accuracy is a concern in systems wherecalibration is either inconvenient or impossible. Morecommonly, absolute accuracy is only a secondary con-cern, as a final trim is performed on the finished productto reconcile the summation of all system inaccuracies. Afinal trim affects considerable cost savings by eliminatingthe need for tight initial accuracy in every reference, DAC,ADC, amplifier and transducer in the system.Monolithic reference initial accuracy ranges from 0.02%to 1%, representing 1LSB error in 6-bit to 12-bit systems.Weston cells and Josephson arrays clock in at 1ppm to10ppm and 0.02ppm initial accuracy, respectively(0.02ppm is less than 1LSB error in a 25-bit sys features a noisefiltering pin). The LT1034 and LTZ1000 buried Zeners areexternally accessible, allowing the user to increase thebias current and reduce noise.Adding output bypassing or external compensation willaffect the character of a reference s noise. In particular, ifthe compensation is peaky, the spot noise will likely riseto a peak somewhere in the 100Hz to 10kHz range. Criticaldamping will eliminate this noise peak.Reference noise can affect the dynamic range of a highresolution system, obscuring small signals. Low fre-quency noise also complicates the measurement of outputvoltage. Modern, high accuracy digital voltmeters canaverage many readings to help filter low frequency noiseeffects and provide a stable reading of a reference s trueoutput voltage.Application Note 82ESSENTIAL FEATURESThere are two styles of references: shunt, functionallyequivalent to a Zener diode; and series, not unlike a3-terminal regulator. Bandgaps and buried Zeners areavailable in both configurations SpecificationsTight initial accuracy is a conc