Current-mode Circuitry Research Articles

A spin transfer torque magnetoresistance random access memory-based high-density and ultralow-power associative memory for fully data-adaptive nearest neighbor search with current-mode similarity evaluation and time-domain minimum searching

A high-density nonvolatile associative memory (NV-AM) based on spin transfer torque magnetoresistive random access memory (STT-MRAM), which achieves highly concurrent and ultralow-power nearest neighbor search with full adaptivity of the template data format, has been proposed and fabricated using the 90 nm CMOS/70 nm perpendicular-magnetic-tunnel-junction hybrid process. A truly compact current-mode circuitry is developed to realize flexibly controllable and high-parallel similarity evaluation, which makes the NV-AM adaptable to any dimensionality and component-bit of template data. A compact dual-stage time-domain minimum searching circuit is also developed, which can freely extend the system for more template data by connecting multiple NM-AM cores without additional circuits for integrated processing. Both the embedded STT-MRAM module and the computing circuit modules in this NV-AM chip are synchronously power-gated to completely eliminate standby power and maximally reduce operation power by only activating the currently accessed circuit blocks. The operations of a prototype chip at 40 MHz are demonstrated by measurement. The average operation power is only 130 µW, and the circuit density is less than 11 µm2/bit. Compared with the latest conventional works in both volatile and nonvolatile approaches, more than 31.3% circuit area reductions and 99.2% power improvements are achieved, respectively. Further power performance analyses are discussed, which verify the special superiority of the proposed NV-AM in low-power and large-memory-based VLSIs.

A Translinear RMS Detector for Embedded Test Of RF ICs

This paper presents a wide-bandwidth, high dynamic range, BiCMOS RF rms detector based on the dynamic translinear principle. A current-domain circuit carries out the main computation, and a circuit compensates for errors due to finite transistor gain. Wide-bandwidth input and output circuits allow connecting voltage-mode signals to the internal current-mode circuitry. Measurements on a prototype chip demonstrate that the circuit is suitable for embedded on-chip testing, particularly for alternative test of RF circuits.

TMR-Based Logic-in-Memory Circuit for Low-Power VLSI

A tunneling magnetoresistive(TMR)-based logic-in-memory circuit, where storage functions are distributed over a logic-circuit plane, is proposed for a low-power VLSI system. Since the TMR device is regarded as a variable resistor with a non-volatile storage capability, any logic functions with external inputs and stored inputs can be performed by using the TMR-based resistor/transistor network. The combination of dynamic current-mode circuitry and a TMR-based logic network makes it possible to perform any switching operations without steady current, which results in power saving. A design example of an SAD unit for MPEG encoding is discussed, and its advantages are demonstrated.

Trends in current analog design - a panel debate

The panel debate at the Eleventh NORCHIP Seminar in Trondheim in 1993 on Trends in Current Analog Design is presented. The presentations of the four panel members included micropower analog computational systems, the digital egg and the analog egg, current mode circuitry, analog CAD tools and analog IC-circuits for mobile telecommunication. Based on the presentations and the following discussion we have summarized the keywords given during the debate. To further underline this topic we have collected in this special issue some key technical publications presented at the 11th NORCHIP seminar.

A 2 V, 10 b, 20 Msample/s, mixed-mode subranging CMOS A/D converter

We have developed a 2 V, 10 b, 20 MS/s, mixed-mode (voltage-mode and current-mode) subranging CMOS A/D Converter (ADC) suitable for video-signal processing systems. Its 2 V supply voltage and 20 mW power consumption are lower than those of any other video-rate ADC reported to date. This ADC employs voltage-mode circuitry for coarse 5 b A/D conversion and current-mode circuitry for fine 6 b A/D conversion. In addition to this mixed-mode subranging architecture, a newly developed differential comparator and a new current-tree A/D conversion architecture also contribute to the achievement of high speed at low supply voltage.