The SST fully-synchronous multi-GHz analog waveform recorder with Nyquist-rate bandwidth and flexible trigger capabilities

The design and performance of a fully-synchronous multi-GHz analog transient waveform recorder I.C. (“SST”) with fast and flexible trigger capabilities is presented. The SST´s objective is to provide multi-GHz sample rates with intrinsically-stable timing, Nyquist-rate sampling and high trigger bandwidth, wide dynamic range and simple operation. Containing 4 channels of 256 samples per channel, the SST is fabricated in an inexpensive 0.25 micrometer CMOS process and uses a high-performance package that is 8 mm on a side. It has a 1.9V input range on a 2.5V supply, exceeds 12 bits of dynamic range, and uses ~128 mW while operating at 2 G-samples/s and full trigger rates. With a standard 50 Ohm input source, the SST exceeds ~1.5 GHz -3 dB bandwidth. The SST´s internal sample clocks are generated synchronously via a shift register driven by an external LVDS oscillator running at half the sample rate (e.g., a 1 GHz oscillator yields 2 G-samples/s). Because of its purely-digital synchronous nature, the SST has ps-level timing uniformity that is independent of sample frequencies spanning over 6 orders of magnitude: from under 2 kHz to over 2 GHz. Only three active control lines are necessary for operation: Reset, Start/Stop and Read-Clock. When operating as common-stop device, the time of the stop, modulo 256 relative to the start, is read out along with the sampled signal values. Each of the four channels integrates dual-threshold trigger circuitry with windowed coincidence features. Channels can discriminate signals with ~1mV RMS resolution at >600 MHz bandwidth. Comparator thresholds can be set individually, and their outputs are directly available for simple threshold monitoring and rate control. Alternatively, their High and Low results can be AND´d over an adjustable window of time in order to exclusively trigger on bipolar impulsive signals. Trigger outputs can be CMOS or low-voltage differential signals, e.g. positive-ECL (0-0.8V) for low-noise operation.