Minimum convertible voltage analysis for ratioless and robust subthreshold level conversion

A Design and Theoretical Analysis of a 145 mV to 1.2 V Single-Ended Level Converter Circuit for Ultra-Low Power Low Voltage ICs

“…This proposed charge pump-based level converter CPBULS up-converts reliably from 145 mV to 1.2 V, which is a wider conversion range. The best energy per conversion is reported as 10 fJ in [10] from simulation results with a 90-nm technology. This work has a relatively lower maximum operating frequency with the lowest input swing, but achieves 1.2 pJ energy per conversion, which is 30% less than that in [8] from chip measurement and a 2× conversion ability.…”

“…[13]. As discussed in the paper and [10], WCMLC is robust, but is not repeatable for the Monte Carlo sizing optimization across different technologies. In [14], they used a three-stage design based on the topology in Figure 2a, which is able to convert from 200 mV to 1.2 V. This cascaded design requires three supply voltages and size adjustment for each of the three intermediate conversion stages, which increases the design and power management complexity.…”

“…Figure 2a,b shows two of the most traditional amplification-based level converter topologies [12]. Following the naming convention in [10], the level converter shown in Figure 2a is the conventional cross-coupled level converter (CCLC), and the level converter shown in Figure 2b is the current mirror-based level converter (CMLC). CCLC is a full-swing design, which can pull up the input low voltage VDDL up to the high voltage rail VDDH by taking advantage of positive feedback.…”

“…This simplified the design of [14] and achieves the conversion from 188 mV in the subthreshold. In this paper, we will note this design as a two-stage CCLC (TSCCLC), as in [10].…”

“…A single-ended interconnect circuit achieves level conversion from 300 mV [9], but it is dynamic and higher power. In [10], a current mirror structure is proposed, which allows the conversion from 200 mV across technologies. A two-stage ULP level converter can convert from 188 mV to 1.2 V achieving ULP operation [11].…”