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High-speed Interfaces Bolster Connectivity in SSD Controllers

August 27, 2019 by Majeed Ahmad

The adoption of PCIe Gen4 and USB 3.2 interface technologies shows how controller chips are trying to match the capacity and speed of flash memory they serve in SSD designs.

The adoption of PCIe Gen4 and USB 3.2 interface technologies shows how controller chips are trying to match the capacity and speed of flash memory they serve in SSD designs.

While flash memory chips are continually innovating their way toward more storage capacity in a single die, what about their counterpart? I'm, of course, referring to flash controller chips, which manage the operation in solid-state drive (SSD) designs. The operating speed of an SSD can degrade when more flash memory chips are connected to a controller interface.

At the same time, however, a rise in the number of interfaces will increase the number of high-speed signal lines, which in turn, makes it hard to implement the wiring on the SSD board. Not surprisingly, therefore, flash controller chipmakers are incorporating higher speed interfaces like PCIe Gen4 and USB 3.2.

4-Channel PCIe Gen4 SSD Controller

Following the AMD’s release of PCIe® 4.0-ready desktop PC platform, which is based on the third-generation AMD Ryzen™ processor and AMD X570 chipset for socket AM4, Marvell has introduced a low-power PCIe® Gen4 NVMe™ SSD controller.

Marvell claims to have designed this storage controller around the challenges that users face in the data center and edge computing environments. With PCIe Gen4, the latest PCI Express specification, a 4-channel controller operating at low power consumption can significantly boost the SSD performance.

 

The SSD reference design built around Marvell’s 88SS1322 PCIe Gen4 NVMe SSD controller. Image from Marvell

 

The DRAM-less PCIe Gen4 SSD controller has been built around the 12 nm process node, and Marvell has validated it with Micron’s 96-layer NAND components supporting 1.2 GT/s interface. It’s compatible with the existing and emerging form factors, including m.2 (22110 to 2230), BGA, EDSFF, and U.2 SSD.

The new SSD controller chip employs Marvell’s NANDEdge™ error correction technology and supports four ONFI and Toggle NAND channels. It can operate at up to 1,200 MT/s to enable high capacity, high throughput, and low latency storage over a wide range of use cases in applications such as data center servers, enterprise boot drives, and storage for PC clients, gaming, and more.

External SSD Controller

Silicon Motion, another supplier of NAND flash controller chips, has unveiled a controller with on-chip USB 3.2 interface, which enables up to two terabytes of storage with the latest generation of 96-layer QLC NAND.

The current portable and external storage designs typically use a stand-alone SSD with a USB to SATA or PCIe bridge chip for the interface between the SSD and the host. The bridge chip connects the controller and flash memory chips.

What Silicon Motion’s SM3282 controller chip does is facilitate a single-chip hardware and software solution that supports the USB Attached SCSI Protocol (UASP) and two NAND channels with four chip enables (CE) per channel.

 

Silicon Motion’s SSD controller comes built-in with 3.3 V/2.5 V/1.8 V/1.2 V voltage regulators and supports LED for indicating access status. Image from Silicon Motion.

 

The SM3282 controller supports USB type A and type C connectors and offers peak sequential read and write transfer speeds of over 400 MB/s. It also enables battery-powered small form factor portable SSDs while offering crystal-less design for bill-of-material (BOM) savings.


 

What's your experience with SSD controllers? Have you used them in your work before? Share your thoughts in the comments below.

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