Jung-Bae Lee

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 1.2 V 12.8 GB/s 2 Gb Mobile Wide-I/O DRAM With 4

Mobile DRAM is widely employed in portable electronic devices due to its feature of low power consumption. Recently, as the market trend renders integration of various features in one chip, mobile DRAM is required to have not only low power consumption but also high capacity and high speed. To attain these goals in mobile DRAM, we designed a 1Gb single data rate (SDR) Wide-I/O mobile SDRAM with 4 channels and 512 DQ pins, featuring 12.8GB/s data bandwidth.

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A major issue in designing a high speed synchronous DRAM (SDRAM) is how to minimize skews, most of which are generated due lo unequal read/write data paths, different enable/disable times between column select lines (CSLs), unequal distribution of clock and unequal cell conditions. In this paper, we will present various circuit techniques for minimization of the skews to achieve the irtaxiiiium intemal clock frequency of a 256M-hit SDRAM.

128 I/Os Using TSV Based Stacking

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.

Skew minimization techniques for 256M-bit synchronous DRAM and beyond

Mobile DRAM is widely adopted in battery-powered portable devices because of its low power. Recently, in mobile devices such as smart phones and tablet PCs, higher performance is required to support 3D gaming mode and high-quality video. These trends lead to consideration of higher-performance DRAMs than LPDDR2, while the power budget for DRAMs for mobile devices cannot increase. DRAMs with wide I/O or serial I/O have been reviewed as candidates for over 6.4GB/s channel bandwidth. However, wide-I/O DRAMs [1] must solve issues such as stacking yield for higher density and failure analysis modeling of system-in-package (SiP), and most serial I/Os have worse I/O power efficiency than LPDDR2. For an evolutionary successor of LPDDR2, therefore, we design a 1.2V 1.6Gb/s/pin ×32 4Gb low-power DDR3 SDRAM (LPDDR3) with input skew calibration and enhanced refresh control schemes, achieving 6.4GB/s total data bandwidth. Most features of LPDDR3 are backward compatible with LPDDR2, except that channel termination, command-address (CA) training, and write leveling are adopted.

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

In a memory system employing wide channel high-performance DRAMs, skews resulting from nonideal system and chip environments become the most critical factor. This 256 MB memory system achieves 256 Gb/s peak bandwidth with a 160 MHz clock and 64b channel using a /spl plusmn/0.4 V-swing, push-pull type I/O interface (SSTL).

A 1.2V 30nm 1.6Gb/s/pin 4Gb LPDDR3 SDRAM with input skew calibration and enhanced control scheme

A technique for reducing the phase error of DLL/PLLs, due to non-ideal characteristics of the charge pump, is proposed. It makes the output of the charge pump virtually grounded, to eliminate the current mismatch and to seamlessly convert the locking information into digital form. A DLL is designed and fabricated to exhibit duty-cycle corrector performance with a speed of 1.4 Gb/s.

A 640 MB/s bi-directional data strobed, double-data-rate SDRAM with a 40 mW DLL circuit for a 256 MB memory system

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 1.4 Gb/s DLL using 2nd order charge-pump scheme with low phase/duty error for high-speed DRAM application

This paper describes DLL (delay locked loop) with built-in DCC (duty cycle correction) capability using a newly proposed coded phase blending scheme. The proposed scheme dramatically improves the DCC range and also enhances the total DLL performance. The DLL has been designed and fabricated within 1G-bit DDR (double data rate) synchronous DRAM using 0.11 /spl mu/m process and the measurement data show that it has unlimited DCC range, faster turn-on speed and smaller jitter compared with our previous work (2001).

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

For chip-to-chip parallel interfaces, maintaining low power consumption while achieving high aggregate bandwidth is the key trend. Forwarded-clock (FC) architecture is well suited to this trend because of the simple structure and inherent correlation of clock and data jitter [1]. Clock-recovery circuits consume a large portion of the I/O power. PLL/DLLs with a phase interpolator are widely used for the clock recovery circuits. However, they dissipate high power and jitter-tracking bandwidth (JTB) is low (PLL) or high (DLL), degrading the jitter correlation between data and clock. Recently, injection-locked oscillators (ILOs) have drawn much attention for the clock-recovery circuit of the FC interfaces due to their low power consumption [3-6]. By de-tuning the free-running frequency of an ILO, clock deskew can be performed and multiphase clocks can be generated without an additional multiphase generator. Also, ILOs can provide JTB of several hundred MHz, which is optimal for the FC interfaces in terms of the jitter correlation and BER [5].