Hoe-ju Chung

8 Gb 3-D DDR3 DRAM Using Through-Silicon-Via Technology

An 8 Gb 4-stack 3-D DDR3 DRAM with through-Si-via is presented which overcomes the limits of conventional modules. A master-slave architecture is proposed which decreases the standby and active power by 50 and 25%, respectively. It also increases the I/O speed to > 1600 Mb/s for 4 rank/module and 2 module/channel case since the master isolates all chip I/O loadings from the channel. Statistical analysis shows that the proposed TSV check and repair scheme can increase the assembly yield up to 98%. By providing extra VDD/VSS edge pads, power noise is reduced to < 100 mV even if all 4 ranks are refreshed every clock cycle consecutively.

A 20nm 1.8V 8Gb PRAM with 40MB/s program bandwidth

Phase-change random access memory (PRAM) is considered as one of the most promising candidates for future memories because of its good scalability and cost-effectiveness [1]. Besides implementations with standard interfaces like NOR flash or LPDDR2-NVM, application-oriented approaches using PRAM as main-memory or storage-class memory have been researched [2-3]. These studies suggest that noticeable merits can be achieved by using PRAM in improving power consumption, system cost, etc. However, relatively low chip density and insufficient write bandwidth of PRAMs are obstacles to better system performance. In this paper, we present an 8Gb PRAM with 40MB/s write bandwidth featuring 8Mb sub-array core architecture with 20nm diode-switched PRAM cells [4]. When an external high voltage is applied, the write bandwidth can be extended as high as 133MB/s.

A 58nm 1.8V 1Gb PRAM with 6.4MB/s program BW

In mobile systems, the demand for the energy saving continues to require a low power memory sub-system. During the last decade, the floating-gate flash memory has been an indispensable low power memory solution. However, NOR flash memory has begun to show difficulties in scaling due to the devices reliability and yield issues. Over the past few years, phase-change random access memory (PRAM) has emerged as an alternative non-volatile memory (NVM) owing to its promising scalability and low cost process [1,2]. In this paper, a PRAM, implemented in a 58nm PRAM process with a low power double-data-rate nonvolatile memory (LPDDR2-N) interface, is presented [3].

A 512-mb DDR3 SDRAM prototype with C/sub IO/ minimization and self-calibration techniques

A 1.5-V 512-Mb DDR3 Synchronous DRAM prototype was designed and fabricated in 80-nm technology. Critical to the signal integrity in DDR3 point-to-2points (P22P) interfacing is an efficient calibration scheme and C IO minimization, which were achieved by on-die-termination (ODT)-merged output drivers, SCR type ESD protection, and self-calibration scheme. The hybrid latency control scheme can turn the DLL off in standby mode, reducing power consumption. User-friendly functions such as temperature read-out from on-chip sensor and per-bank-refresh were also implemented.

25.1 A 3.2Gb/s/pin 8Gb 1.0V LPDDR4 SDRAM with integrated ECC engine for sub-1V DRAM core operation

The recent revolution in handheld computing with high-speed cellular network made mobile processors have multi-cores and powerful 3D graphic engines that support FHD (1920×1080) or even higher resolutions. Consequently, the memory bandwidth requirement has also been increasing, requiring a next-generation mobile DRAM standard. In this paper, we present a power-efficient LPDDR4 SDRAM operating at 3.2Gb/s/pin. Our LPDDR4 DRAM offers 2× bandwidth with improved power efficiency over LPDDR3 SDRAMs, due to the 2-channel architecture and low-voltage-swing terminated logic (LVSTL) [1]. Moreover, the supply voltage is further reduced to 1.0V in this work, 0.1V lower than the LPDDR4 standard, for extra power saving.

A 3.2 Gbps/pin 8 Gbit 1.0 V LPDDR4 SDRAM With Integrated ECC Engine for Sub-1 V DRAM Core Operation

A 1.0 V 8 Gbit LPDDR4 SDRAM with 3.2 Gbps/pin speed and integrated ECC engine for sub-1 V DRAM core is presented. DRAM internal read-modify-write operation for data masked write makes the integrated ECC engine possible in a commodity DRAM. Time interleaved latency and IO control circuits enable 1.0 V operation at target speed. To reach 3.2 Gbps with improved power efficiency over conventional mobile DRAMs, the following IO features are introduced: Low voltage swing terminated logic drivers with VOH level calibration and periodic ZQ calibration, unmatched DQ/DQS scheme and DQS oscillator for DQS tree delay tracking. This chip is fabricated in 25 nm DRAM process on 88.1 mm 2 die area.

An 8 Gb/s/pin 9.6 ns Row-Cycle 288 Mb Deca-Data Rate SDRAM With an I/O Error Detection Scheme

This paper proposes a deca-data rate clocking scheme and relevant I/O circuit techniques for a multi-Gb/s/pin memory interface. A deca-data rate scheme transmits 10 bits in one external clock cycle to transfer an error control code along with original data seamlessly without a timing bubble. A 288 Mb SDRAM has been designed using the proposed scheme combined with fast cycling core techniques to have both high I/O bandwidth and fast random cycling. Measured results show that the chip exhibits per-pin data rate of 8 Gb/s and row cycle time of 9.6 ns

A 512Mbit, 3.2Gbps/pin packet-based DRAM with cost-efficient clock generation and distribution scheme

A 1.8V, 512Mbit Packet-based DRAM with 3.2Gbps/pin was designed for main memory of a game console and graphic application. To have lower power consumption and smaller area in clock generation and distribution, 3-row pad structure with reduced clock loading and PLL with loop zero from voltage offset are used. An analytical equation for estimating the input capacitance of pad with ODT (On-Die Termination) is also presented.

BER Measurement of a 5.8-Gb/s/pin Unidirectional Differential I/O for DRAM Application With DIMM Channel

A 1-Gbit DRAM with 5.8-Gb/s/pin unidirectional differential I/Os was implemented by 70 nm DRAM process and a main memory module with dual in-line memory module was assembled. The implemented DRAM chips have control methods for core noise injection and a cyclic redundancy check (CRC) generator for outer-data inner-command architecture. Measurements for bit error rate and jitter performance of the transmitter was performed on an electrical test board which emulates the real memory systems environment. Also, the effect on power noise was analyzed from the DRAM chips with three class values of power decoupling capacitance for the peripheral part. The results show that no additional coding for the differential I/O protection in DRAM, like CRC, is required up to 5.8-Gb/s/pin operation.

Channel BER Measurement for a 5.8Gb/s/pin unidirectional differential I/O for DRAM application

A 5.8 Gb/s/pin DRAM with unidirectional differential I/Os and 1 Gbit memory core was designed and 23.2 GB/s memory module was assembled. Tx BER measurement on an electrical test board similar to real memory sub-systempsilas environment was performed and the results show that no additional coding for the differential I/O protection, like CRC, seems to be required up to 5.8 Gb/s/pin operation. Also, an efficient timing usage method using matched path for a possible implementation of CRC computation in ODIC architecture was proposed.