Tetsuya Fujita

A 0.9-V, 150-MHz, 10-mW, 4 mm/sup 2/, 2-D discrete cosine transform core processor with variable threshold-voltage (VT) scheme

This two-dimensional 8/spl times/8 discrete cosine transform (DCT) core processor for portable multimedia equipment with HDTV-resolution in a 0.3 /spl mu/m CMOS triple-well double-metal technology operates at 150 MHz from a 0.9 V power supply and consumes 10 mW, only 2% power dissipation of a previous 3.3 V DCT. Circuit techniques for dynamically varying threshold voltage reduce active power dissipation with negligible overhead in speed, standby power and chip area.

Variable supply-voltage scheme for low-power high-speed CMOS digital design

This paper describes a variable supply-voltage (VS) scheme. From an external supply, the VS scheme automatically generates minimum internal supply voltages by feedback control of a buck converter, a speed detector, and a timing controller so that they meet the demand on its operation frequency. A 32-b RISC core processor is developed in a 0.4-/spl mu/m CMOS technology which optimally controls the internal supple voltages with the VS scheme and the threshold voltages through substrate bias control. Performance in MIPS/W is improved by a factor of more than two compared with its conventional CMOS design.

A 60 mW MPEG4 video codec using clustered voltage scaling with variable supply-voltage scheme

This MPEG4 video codec implements essential functions in the MPEG4 committee draft. It consumes 60 mW at 30 MHz, 30% of the power dissipation of a conventional CMOS design. Measured power dissipation is summarized. 70% power reduction is achieved by low-power techniques at circuit and architectural levels. A 16b RISC processor provides software programmability. Binary shape decoding uses 20% of the computation power of the RISC processor at 30MHz clock, with negligible increase in chip power dissipation. Three-step hierarchical motion estimation reduces power dissipation.

A single-chip 802.11a MAC/PHY with a 32 b RISC processor

An 802.11a compliant MAC/PHY processing chip has been successfully fabricated in 0.18 /spl mu/m CMOS. Thirty million transistors are integrated on a 10.91 /spl times/ 10.91 mm/sup 2/ die in a 361-pin PFBGA. The MAC functions are fully implemented by firmware on an embedded 32 b RISC processor and hardware acceleration logic. The PHY supports a complete set of data rates up to 54 Mb/s.

A high-speed low-power 0.3 /spl mu/m CMOS gate array with variable threshold voltage (VT) scheme

Circuit techniques for dynamically varying threshold voltage are introduced to reduce active power dissipation by 50% with negligible overhead in speed, standby power and chip area. No additional external power supply or additional step in process is required. A gate array with this scheme is fabricated in a 0.3 /spl mu/m CMOS technology whose performance is investigated. The gate array is best fit for multimedia portable applications that require low standby power dissipation and high performance.

Conditional Data Mapping Flip-Flops for Low-Power and High-Performance Systems

This paper introduces a new family of low-power and high-performance flip-flops, namely conditional data mapping flip-flops (CDMFFs), which reduce their dynamic power by mapping their inputs to a configuration that eliminates redundant internal transitions. We present two CDMFFs, having differential and single-ended structures, respectively, and compare them to the state-of-the-art flip-flops. The results indicate that both CDMFFs have the best power-delay product in their groups, respectively. In the aspect of power dissipation, the single-ended and differential CDMFFs consume the least power at data activity less than 50%, and are 31% and 26% less power than the conditional capture flip-flops at 25% data activity, respectively. In the aspect of performance, CDMFFs achieve small data-to-output delays, comparable to those of the transmission-gate pulsed latch and the modified-sense-amplifier flip-flop. In the aspect of timing reliability, CDMFFs have the best internal race immunity among pulse-triggered flip-flops. A post-layout case study is demonstrated with comparison to a transmission-gate flip-flop. The results indicate the single-ended CDMFF has 34% less in data-to-output delay and 28% less in power at 25% data activity, in spite of the 34% increase in size

A 300 MIPS/W RISC core processor with variable supply-voltage scheme in variable threshold-voltage CMOS

A 300 MIPS/W RISC core processor with variable supply-voltage (VS) scheme in variable threshold-voltage CMOS (VTCMOS) is presented. Performance in MIPS/W can be improved by a factor of more than two with no modification in the RISC core except for substrate contacts for the VTCMOS. From a 3.3 V external power supply the VS scheme automatically generates minimum internal supply voltages which meet the demand on its operation frequency.

A 63-mW H.264/MPEG-4 audio/visual codec LSI with module-wise dynamic Voltage/frequency scaling

A single-chip H.264 and MPEG-4 audio-visual LSI for mobile applications including terrestrial digital broadcasting system (ISDB-T / DVB-H) with a module-wise, dynamic voltage/frequency scaling architecture is presented for the first time. This LSI can keep operating even during the voltage/frequency transition, so there is no performance overhead. It is realized through a dynamic deskewing system and an on-chip voltage regulator with slew rate control. By the combination with traditional low power techniques such as embedded DRAM and clock gating, it consumes only 63 mW in decoding QVGA H.264 video at 15 frames/sec and MPEG-4 AAC LC audio simultaneously.

A 77% energy-saving 22-transistor single-phase-clocking D-flip-flop with adaptive-coupling configuration in 40nm CMOS

Flip-flops (FF) typically consume more than 50% of random-logic power in an SoC chip, due to their redundant transition of internal nodes, when the input and the output are in the same state. Several low-power techniques have been proposed [1–5], but all of them incur transistor-count penalties, leading to an increase in size, which is too costly since flip-flops typically account for 50% of random-logic area. In this work, we design and test a D-flip-flop, known as adaptive-coupling flip-flop (ACFF), which has a reduced transistor count compared to other low-power flip-flops, and 2 fewer transistors than the mainstream transmission-gate flip-flop (TGFF). ACFF features a single-phase clocking structure, with no local clock buffer and no precharging stage, enabling it to be more energy efficient than TGFF, where up to 77% energy saving is achieved at 0% data activity. ACFF also has an adaptive-coupling configuration, which weakens state-retention coupling during a transition, allowing it to be tolerant to process variations. Test chips are fabricated in a 40nm CMOS technology for 1.1V application, and 500k ACFFs are tested over all chips in 5 skew wafers. All tested ACFFs are fully functional down to 0.75V supply voltage, with spreads of timing parameters comparable to TGFF. We also demonstrate a P&R test by employing ACFF to a wireless LAN chip, and the results indicate chip power is reduced by as much as 24%.

A 160 mW, 80 nA standby, MPEG-4 audiovisual LSI with 16 Mb embedded DRAM and a 5 GOPS adaptive post filter

A single-chip MPEG-4 audiovisual LSI in a 0.13 /spl mu/m 5M CMOS technology with 16 Mb embedded DRAM is presented. Four 16 b RISC processors and dedicated hardware accelerators including a 5 GOPS post filtering engine are integrated on the IC. The chip consumes 160 mW at 125 MHz and uses 80 nA in the standby mode. This LSI handles MPEG-4 CIF video encoding at 15 frames/s and audio encoding simultaneously.