High-precision voltage reference with integrated ADC drive buffer

Most SAR ADCs, and a few delta-sigma ADCs, switch binary-weighted capacitors onto the REF pin during the conversion process, say Texas Instruments. The magnitude of the capacitance switched onto the REF pin during each conversion depends on the input signal to the ADC. In order to support this dynamic load and preserve the ADC linearity, distortion and noise performance, the output of the voltage reference must be buffered with a low-output impedance (high-bandwidth) buffer. The REF60xx family of voltage references have an integrated low output impedance buffer that enable the user to directly drive the REF pin of a successive approximation register analog-to-digital converter (ADC), while preserving ADC linearity, distortion, and noise performance. In addition, the output voltage of the series does not droop below 1 LSB (18-bit), even during the first conversion while driving the REF pin of the ADS8881. This feature is extremely useful in burst-mode, event-triggered, equivalent-time sampling, and variable-sampling-rate data-acquisition systems. The devices offer excellent temperature drift of just 5 ppm/degC, and high initial accuracy of 0.05% for both the band-gap voltage reference and the low output impedance buffer combined, while operating at a typical quiescent current of 820 µA. They are well suited, but not limited, to drive the REF pin of the ADS88xx family of SAR ADCs and ADS127xx family of delta-sigma ADCs. This high-precision voltage reference with integrated high-bandwidth buffer is suitable for use with ATE testers and oscilloscopes, test and measurement equipment, analog input modules for PLCs, medical equipment and precision data acquisition systems.