Embedded Measurement of GHz Digital Signals With Time Amplification in CMOS

This paper examines an embedded low-power technique for the single-shot measurement of GHz digital signals. Two circuits will be demonstrated; the first is a rise time measurement core, while the second represents an embedded technique for the characterization of narrow pulses. Both circuits can be seen as general tools to increase the low-end time dynamic range measurements of digital events in CMOS. The circuits rely on a new fast voltage-crossing detector to convert the input information and condition it into same polarity edges, separated by the timing information to be measured. Those edges are then in turn stretched further using time amplification, making them easily detectable with low-resolution time-to-digital converters. Dynamic current generation techniques are used in the front-end detector to greatly reduce the power consumption. The proposed circuits are compact and introduce only a few tens of femtofarads capacitive loading. The circuits were implemented in a standard 0.18-mum CMOS process. Experimental results show the feasibility of the proposed approach. Rise times of 1 ns and pulses as narrow as 78 ps were successfully captured in a single-shot measurement approach, with total power dissipation not exceeding a few milliwatts, in each of the two cases.