SAR ADC for simultaneous precision measurement and fast signal tracking

Linear Technology Corporation has introduced the LTC2508-32, an ultra-high precision 32-bit successive approximation register (SAR) ADC. Many high performance applications, including data acquisition, industrial control and medical instrumentation, require both accuracy and speed. This is often achieved by using a high resolution delta-sigma ADC and a high speed SAR ADC in the same system. The device simplifies such hybrid ADC system design by simultaneously providing both a 32-bit low noise digitally filtered output and a 14-bit 1Msps no latency output. Since these outputs are generated from a single 32-bit SAR ADC core, the high accuracy and high speed outputs are perfectly matched, even as the operating temperature, supply and stress vary. In contrast to traditional solutions employing two distinct unmatched ADCs, the unique combination of both accuracy and speed in the device enables much higher system performance while reducing solution size and lowering component count. It is ideal for applications that simultaneously require precision measurement and fast tracking of signals. The exceptional 3.5ppm guaranteed maximum linearity, together with up to 145dB of dynamic range, enables the device to make precision measurements in the presence of noise. Simultaneously, the high speed 1Msps output provides a 14-bit differential and 8-bit common mode representation of the input signal, enabling sophisticated control loop designs with early detection mechanisms. It further improves system accuracy while simplifying signal conditioning design by directly digitising the input signal over the full input range with over 120dB of common mode rejection. The device features an integrated digital filter that can be configured to optimise the 32-bit high accuracy output’s noise performance and bandwidth, up to a maximum 145dB of dynamic range at an output data rate of 61sps. The integrated digital filter offers a minimum 80dB attenuation of out-of-band noise, relaxing analog anti-aliasing filter requirements and significantly reducing system complexity. The reduced data rate of the digitally filtered output also eases communication with slow processors.