1ppm Settling Time Measurement for a New Monolithic DAC

The LTC2757, a new 18-bit DAC, requires careful measurement techniques to verify performance. Performance verification at DC is relatively straightforward using precision DVMs. Dynamic conditions considerably complicate measurement. In particular, determining DAC settling within 10 microvolts after a 10-volt step with a 275 nanosecond measurement resolution limit requires trustworthy instrumentation and investigator prudence. This video, based on LTC application note 120, describes a technique enabling an oscilloscope to accurately display DAC settling information with 1ppm resolution. The approach employed permits observation of small amplitude information at the excursion limits of large waveforms without overdriving the oscilloscope. Measuring anything at any speed to 1ppm (.0001%) is hard. Dynamic measurement to this resolution is particularly challenging. Reliable 1ppm settling time measurement constitutes a high order difficulty problem requiring care in approach and experimental technique.