Mobile DDR: Samsung K4X2G323PD-8GD8

Low-Power Double Data Rate (LPDDR), also known as LPDDR SDRAM, is a type of synchronous dynamic random-access memory that consumes less power and is targeted for mobile computers and devices such as mobile phones. Older variants are also known as Mobile DDR, and abbreviated as mDDR.

Modern LPDDR SDRAM is distinct from DDR SDRAM, with various differences that make the technology more appropriate for the mobile application.[1] LPDDR technology standards are developed independently of DDR standards, with LPDDR4X and even LPDDR5 for example being implemented prior to DDR5 SDRAM and offering far higher data rates than DDR4 SDRAM.

Bus width

Properties of the different LPDDR generations
LPDDR 1 1E 2 2E 3 3E 4 4X 5 5X
Maximum density (bit) 32 64 64 32 32
Memory array clock (MHz) 200 266 200 266 200 266 200 266 400 533
Prefetch size 2n 4n 8n 16n
Memory densities 64 Mbit – 8 Gbit 1–32 Gbit 4–32 Gbit 4–32 Gbit
I/O bus clock frequency (MHz) 200 266 400 0533 0800 1067 1600 2133 3200 4267
Data transfer rate, DDR (MT/s)[a] 400 533 800 1067 1600 2133 3200 4267 6400 8533
Supply voltages (volts) 1.8 1.2, 1.8 1.2, 1.8 1.1, 1.8 0.6, 1.1, 1.8 0.5, 1.05, 1.8 0.5, 1.05, 1.8
Command/address bus 19 bits, SDR 10 bits, DDR 6 bits, SDR 7 bits, DDR
Year ? 2009 2012 2014 2017 2019 2021

In contrast with standard SDRAM, used in stationary devices and laptops and usually connected over a 64-bit wide memory bus, LPDDR also permits 16- or 32-bit wide channels.[2]

The "E" and "X" versions mark enhanced versions of the specifications. They formalize overclocking the memory array by usually 33%.

As with standard SDRAM, most generations double the internal fetch size and external transfer speed. (DDR4 and LPDDR5 being the exceptions.)

Generations

LPDDR(1)

The original low-power DDR (sometimes retroactively called LPDDR1) is a slightly modified form of DDR SDRAM, with several changes to reduce overall power consumption.

Most significantly, the supply voltage is reduced from 2.5 to 1.8 V. Additional savings come from temperature-compensated refresh (DRAM requires refresh less often at low temperatures), partial array self refresh, and a "deep power down" mode which sacrifices all memory contents. Additionally, chips are smaller, using less board space than their non-mobile equivalents. Samsung and Micron are two of the main providers of this technology, which is used in tablet and phone devices such as the iPhone 3GS, original iPad, Samsung Galaxy Tab 7.0 and Motorola Droid X.[3]

LPDDR2

Samsung K4P4G154EC-FGC1 4 Gbit LPDDR2 chip

In 2009, the standards group JEDEC published JESD209-2, which defined a more dramatically revised low-power DDR interface.[4][5] It is not compatible with either DDR1 or DDR2 SDRAM, but can accommodate either:

Low-power states are similar to basic LPDDR, with some additional partial array refresh options.

Timing parameters are specified for LPDDR-200 to LPDDR-1066 (clock frequencies of 100 to 533 MHz).

Working at 1.2 V, LPDDR2 multiplexes the control and address lines onto a 10-bit double data rate CA bus. The commands are similar to those of normal SDRAM, except for the reassignment of the precharge and burst terminate opcodes:

LPDDR2/LPDDR3 command encoding[4]
Operation Rising clock Falling clock
CA0
(RAS)
CA1
(CAS)
CA2
(WE)
CA3
 
CA4
 
CA5
 
CA6
 
CA7
 
CA8
 
CA9
 
CA0
(RAS)
CA1
(CAS)
CA2
(WE)
CA3
 
CA4
 
CA5
 
CA6
 
CA7
 
CA8
 
CA9
 
No operation H H H
Precharge all banks H H L H H
Precharge one bank H H L H L BA0 BA1 BA2
Preactive (LPDDR2-N only) H H L H A30 A31 A32 BA0 BA1 BA2 A20 A21 A22 A23 A24 A25 A26 A27 A28 A29
Burst terminate H H L L
Read (AP=auto-precharge) H L H reserved C1 C2 BA0 BA1 BA2 AP C3 C4 C5 C6 C7 C8 C9 C10 C11
Write (AP=auto-precharge) H L L reserved C1 C2 BA0 BA1 BA2 AP C3 C4 C5 C6 C7 C8 C9 C10 C11
Activate (R0–14=Row address) L H R8 R9 R10 R11 R12 BA0 BA1 BA2 R0 R1 R2 R3 R4 R5 R6 R7 R13 R14
Activate (LPDDR2-N only) L H A15 A16 A17 A18 A19 BA0 BA1 BA2 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14
Refresh all banks (LPDDR2-Sx only) L L H H
Refresh one bank (round-robin addressing) L L H L
Mode register read (MA0–7=address) L L L H MA0 MA1 MA2 MA3 MA4 MA5 MA6 MA7
Mode register write (OP0–7=data) L L L L MA0 MA1 MA2 MA3 MA4 MA5 MA6 MA7 OP0 OP1 OP2 OP3 OP4 OP5 OP6 OP7

Column address bit C0 is never transferred, and is assumed to be zero. Burst transfers thus always begin at even addresses.

LPDDR2 also has an active-low chip select (when high, everything is a NOP) and clock enable CKE signal, which operate like SDRAM. Also like SDRAM, the command sent on the cycle that CKE is first dropped selects the power-down state:

The mode registers have been greatly expanded compared to conventional SDRAM, with an 8-bit address space, and the ability to read them back. Although smaller than a serial presence detect EEPROM, enough information is included to eliminate the need for one.

S2 devices smaller than 4 Gbit, and S4 devices smaller than 1 Gbit have only four banks. They ignore the BA2 signal, and do not support per-bank refresh.

Non-volatile memory devices do not use the refresh commands, and reassign the precharge command to transfer address bits A20 and up. The low-order bits (A19 and down) are transferred by a following Activate command. This transfers the selected row from the memory array to one of 4 or 8 (selected by the BA bits) row data buffers, where they can be read by a Read command. Unlike DRAM, the bank address bits are not part of the memory address; any address can be transferred to any row data buffer. A row data buffer may be from 32 to 4096 bytes long, depending on the type of memory. Rows larger than 32 bytes ignore some of the low-order address bits in the Activate command. Rows smaller than 4096 bytes ignore some of the high-order address bits in the Read command.

Non-volatile memory does not support the Write command to row data buffers. Rather, a series of control registers in a special address region support Read and Write commands, which can be used to erase and program the memory array.

LPDDR3

In May 2012, JEDEC published the JESD209-3 Low Power Memory Device Standard.[6][7][8] In comparison to LPDDR2, LPDDR3 offers a higher data rate, greater bandwidth and power efficiency, and higher memory density. LPDDR3 achieves a data rate of 1600 MT/s and utilizes key new technologies: write-leveling and command/address training,[9] optional on-die termination (ODT), and low-I/O capacitance. LPDDR3 supports both package-on-package (PoP) and discrete packaging types.

The command encoding is identical to LPDDR2, using a 10-bit double data rate CA bus.[7] However, the standard only specifies 8n-prefetch DRAM, and does not include the flash memory commands.

Products using LPDDR3 include the 2013 MacBook Air, iPhone 5S, iPhone 6, Nexus 10, Samsung Galaxy S4 (GT-I9500) and Microsoft Surface Pro 3 and 4.[10] LPDDR3 went mainstream in 2013, running at 800 MHz DDR (1600 MT/s), offering bandwidth comparable to PC3-12800 notebook memory in 2011 (12.8 GB/s of bandwidth).[11] To achieve this bandwidth, the controller must implement dual-channel memory. For example, this is the case for the Exynos 5 Dual[12] and the 5 Octa.[13]

LPDDR3E

An "enhanced" version of the specification called LPDDR3E increases the data rate to 2133 MT/s. Samsung Electronics introduced the first 4 gigabit 20 nm-class LPDDR3 modules capable of transmitting data at up to 2,133 MT/s, more than double the performance of the older LPDDR2 which is only capable of 800 MT/s.[14] Various SoCs from various manufacturers also natively support 800 MHz LPDDR3 RAM. Such include the Snapdragon 600 and 800 from Qualcomm[15] as well as some SoCs from the Exynos and Allwinner series.

LPDDR4

On 14 March 2012, JEDEC hosted a conference to explore how future mobile device requirements will drive upcoming standards like LPDDR4.[16] On 30 December 2013, Samsung announced that it had developed the first 20 nm-class 8 gigabit (1 GB) LPDDR4 capable of transmitting data at 3,200 MT/s, thus providing 50 percent higher performance than the fastest LPDDR3 and consuming around 40 percent less energy at 1.1 volts.[17][18]

On 25 August 2014, JEDEC published the JESD209-4 LPDDR4 Low Power Memory Device Standard.[19][20]

Significant changes include:

The standard defines SDRAM packages containing two independent 16-bit access channels, each connected to up to two dies per package. Each channel is 16 data bits wide, has its own control/address pins, and allows access to 8 banks of DRAM. Thus, the package may be connected in three ways:

Each die provides 4, 6, 8, 12, or 16 gigabits of memory, half to each channel. Thus, each bank is one sixteenth the device size. This is organized into the appropriate number (16 K to 64 K) of 16384-bit (2048-byte) rows. Extension to 24 and 32 gigabits is planned, but it is not yet decided if this will be done by increasing the number of rows, their width, or the number of banks.

Larger packages providing double width (four channels) and up to four dies per pair of channels (8 dies total per package) are also defined.

Data is accessed in bursts of either 16 or 32 transfers (256 or 512 bits, 32 or 64 bytes, 8 or 16 cycles DDR). Bursts must begin on 64-bit boundaries.

Since the clock frequency is higher and the minimum burst length longer than earlier standards, control signals can be more highly multiplexed without the command/address bus becoming a bottleneck. LPDDR4 multiplexes the control and address lines onto a 6-bit single data rate CA bus. Commands require 2 clock cycles, and operations encoding an address (e.g., activate row, read or write column) require two commands. For example, to request a read from an idle chip requires four commands taking 8 clock cycles: Activate-1, Activate-2, Read, CAS-2.

The chip select line (CS) is active-high. The first cycle of a command is identified by chip select being high; it is low during the second cycle.

LPDDR4 command encoding[20]: 151 
First cycle (CS high) Second cycle (CS low) Operation
CA5 CA4 CA3 CA2 CA1 CA0 CA5 CA4 CA3 CA2 CA1 CA0
L L L L L L No operation
H L L L L L 0 OP4 OP3 OP2 OP1 1 Multi-purpose command
AB H L L L L BA2 BA1 BA0 Precharge (AB: all banks)
AB L H L L L BA2 BA1 BA0 Refresh (AB: all banks)
H H L L L Self-refresh entry
BL L L H L L AP C9 BA2 BA1 BA0 Write-1 (+CAS-2)
H L H L L Self-refresh exit
0 L H H L L AP C9 BA2 BA1 BA0 Masked write-1 (+CAS-2)
H H H L L Reserved
BL L L L H L AP C9 BA2 BA1 BA0 Read-1 (+CAS-2)
C8 H L L H L C7 C6 C5 C4 C3 C2 CAS-2
H L H L Reserved
OP7 L L H H L MA5 MA4 MA3 MA2 MA1 MA0 Mode register write-1 and -2
MA: address, OP: data
OP6 H L H H L OP5 OP4 OP3 OP2 OP1 OP0
L H H H L MA5 MA4 MA3 MA2 MA1 MA0 Mode register read (+CAS-2)
H H H H L Reserved
R15 R14 R13 R12 L H R11 R10 R16 BA2 BA1 BA0 Activate-1 and -2
R9 R8 R7 R6 H H R5 R4 R3 R2 R1 R0

The CAS-2 command is used as the second half of all commands that perform a transfer across the data bus, and provides low-order column address bits:

The burst length can be configured to be 16, 32, or dynamically selectable by the BL bit of read and write operations.

One DMI (data mask/invert) signal is associated with each 8 data lines, and can be used to minimize the number of bits driven high during data transfers. When high, the other 8 bits are complemented by both transmitter and receiver. If a byte contains five or more 1 bits, the DMI signal can be driven high, along with three or fewer data lines. As signal lines are terminated low, this reduces power consumption.

(An alternative usage, where DMI is used to limit the number of data lines which toggle on each transfer to at most 4, minimises crosstalk. This may be used by the memory controller during writes, but is not supported by the memory devices.)

Data bus inversion can be separately enabled for reads and writes. For masked writes (which have a separate command code), the operation of the DMI signal depends on whether write inversion is enabled.

LPDDR4 also includes a mechanism for "targeted row refresh" to avoid corruption due to "row hammer" on adjacent rows. A special sequence of three activate/precharge sequences specifies the row which was activated more often than a device-specified threshold (200,000 to 700,000 per refresh cycle). Internally, the device refreshes physically adjacent rows rather than the one specified in the activate command.[21][20]: 153–54 

LPDDR4X

Samsung Semiconductor proposed an LPDDR4 variant that it called LPDDR4X.[22]: 11  LPDDR4X is identical to LPDDR4 except additional power is saved by reducing the I/O voltage (Vddq) from 1.1 V to 0.6 V. On 9 January 2017, SK Hynix announced 8 and 16 GB LPDDR4X packages.[23][24] JEDEC published the LPDDR4X standard on 8 March 2017.[25] Aside from the lower voltage, additional improvements include a single-channel die option for smaller applications, new MCP, PoP and IoT packages, and additional definition and timing improvements for the highest 4266 MT/s speed grade.

LPDDR5

On 19 February 2019, JEDEC published the JESD209-5, Standard for Low Power Double Data Rate 5 (LPDDR5).[26]

Samsung announced it had working prototype LPDDR5 chips in July 2018. LPDDR5 introduces the following changes:[27]

AMD Van Gogh, Intel Tiger Lake, Apple silicon (M1 Pro, M1 Max, M1 Ultra, M2 and A16 Bionic), Huawei Kirin 9000 and Snapdragon 888 memory controllers support LPDDR5.

The doubling of the transfer rate, and the quarter-speed master clock, results in a master clock which is half the frequency of a similar LPDDR4 clock. The command (CA) bus is widened to 7 bits, and commands are transferred at double data rate, so commands end up being sent at the same rate as LPDDR4.

LPDDR5 command encoding[28][29]
↗ Rising clock ↗ ↘ Falling clock ↘ Operation
CA6 CA5 CA4 CA3 CA2 CA1 CA0 CA6 CA5 CA4 CA3 CA2 CA1 CA0
L L L L L L L No operation
H L L L L L L Power-down entry
L H L L L L L — L — Read FIFO
H H L L L L L — L — Write FIFO
L L H L L L L Reserved
H L H L L L L — L — Read DQ Calibration
OP7 H H L L L L OP6 OP5 OP4 OP3 OP2 OP1 OP0 Multi-purpose command
OP7 L L H L L L OP6 OP5 OP4 OP3 OP2 OP1 OP0 Mode register write 2
L H L H L L L Self-refresh exit
H H L H L L L PD DSE Self-refresh entry
L L H H L L L MA6 MA5 MA4 MA3 MA2 MA1 MA0 Mode register read
H L H H L L L MA6 MA5 MA4 MA3 MA2 MA1 MA0 Mode register write 1
L H H H L L L AB SB1 SB0 RFM BG0 BA1 BA0 Refresh
H H H H L L L AB BG1 BG0 BA1 BA0 Precharge
C5 C4 C3 L H L L AP C2 C1 BG1 BG0 BA1 BA0 Write 32
WS_
FS
WS_
RD
WS_
WR
H H L L WXSB
/B3
WXSA WRX DC3 DC2 DC1 DC0 Column address select
C5 C4 C3 C0 L H L AP C2 C1 BG1 BG0 BA1 BA0 Masked Write
C5 C4 C3 C0 H H L AP C2 C1 BG1 BG0 BA1 BA0 Write
C5 C4 C3 C0 L L H AP C2 C1 BG1 BG0 BA1 BA0 Read
C5 C4 C3 C0 H L H AP C2 C1 BG1 BG0 BA1 BA0 Read 32
R10 R9 R8 R7 L H H R6 R5 R4 R3 R2 R1 R0 Activate 2
R17 R16 R15 R14 H H H R13 R12 R11 BG1 BG0 BA1 BA0 Activate 1

Compared to earlier standards, the nomenclature for column addresses has changed. Both LPDDR4 and LPDDR5 allow up to 10 bits of column address, but the names are different. LPDDR4's C0–C9 are renamed B0–B3 and C0–C5. As with LPDDR4, writes must start at a multiple-of-16 address with B0–B3 zero, but reads may request a burst be transferred in a different order by specifying a non-zero value for B3.

As with LPDDR4, to read some data requires 4 commands: two activate commands to select a row, then a CAS and a read command to select a column. Unlike LPDDR4, the CAS command comes before the read or write command. In fact, it is something of a misnomer, in that it does not select a column at all. Instead, its primary function is to prepare the DRAM to synchronize with the imminent start of the high-speed WCK clock. The WS_FS, WS_RD and WS_WR bits select various timings, with the _RD and _WR options optimized for an immediately following read or write command, while the _FS option starts the clock immediately, and may be followed by multiple reads or writes, accessing multiple banks.

CAS also specifies the "write X" option. If the WRX bit is set, writes do not transfer data, but rather fill the burst with all-zeros or all-ones, under the control of the WXS (write-X select) bit. This takes the same amount of time, but saves energy.

In addition to the usual bursts of 16, there are commands for performing double-length bursts of 32. Reads (but not writes) may specify a starting position within the 32-word aligned burst using the C0 and B3 bits.

LPDDR5X

On 28 July 2021, JEDEC published the JESD209-5B, Standard for Low Power Double Data Rate 5X (LPDDR5X)[30] with the following changes:

On 9 November 2021, Samsung announced that the company has developed the industry's first LPDDR5X DRAM. Samsung's implementation involves 16-gigabit (2GB) dies, on a 14 nm process node, with modules with up to 32 dies (64GB) in a single package. According to the company, the new modules would use 20% less power than LPDDR5.[31] According to Andrei Frumusanu of AnandTech, LPDDR5X in SoCs and other products was expected for the 2023 generation of devices.[32]

On 19 November 2021, Micron announced that Mediatek has validated its LPDDR5X DRAM for Mediatek's Dimensity 9000 5G SoC.[33]

LPDDR5T

On 25 January 2023 SK Hynix announced LPDDR5 chips with a bandwidth of 9.6 Gbps, 13% higher than LPDDR5X. Hynix calls this extension "LPDDR5 Turbo" (LPDDR5T).[34] It operates in the 1.01–1.12 V supply voltage range.

MediaTek Dimensity 9300 supports LPDDR5T.

Notes

  1. ^ Equivalently, Mbit/s·pin.

References

  1. ^ "When is LPDDR3 not LPDDR3? When it's DDR3L..." Committed to Memory blog. Retrieved 16 July 2021.
  2. ^ "LPDDR". Texas Instruments wiki. Archived from the original on 5 March 2012. Retrieved 10 March 2015.
  3. ^ Anandtech Samsung Galaxy Tab - The AnandTech Review, 23 December 2010
  4. ^ a b JEDEC Standard: Low Power Double Data Rate 2 (LPDDR2) (PDF), JEDEC Solid State Technology Association, February 2010, retrieved 30 December 2010
  5. ^ "JEDEC Announces Publication of LPDDR2 Standard for Low Power Memory Devices". Press release. 2 April 2009. Retrieved 28 November 2021.
  6. ^ JEDEC publishes LPDDR3 standard for low-power memory chips Archived 20 May 2012 at the Wayback Machine, Solid State Technology magazine
  7. ^ a b JESD209-3 LPDDR3 Low Power Memory Device Standard, JEDEC Solid State Technology Association
  8. ^ "JEDEC Announces Publication of LPDDR3 Standard for Low Power Memory Devices". jedec.org. Retrieved 10 March 2015.
  9. ^ Want a quick and dirty overview of the new JEDEC LPDDR3 spec? EETimes serves it up Archived 2013-07-28 at the Wayback Machine, Denali Memory Report
  10. ^ Inside the Samsung Galaxy S4 Archived 2013-04-29 at the Wayback Machine, Chipworks
  11. ^ Samsung LPDDR3 High-Performance Memory Enables Amazing Mobile Devices in 2013, 2014 - Bright Side of News
  12. ^ "Samsung Exynos". samsung.com. Retrieved 10 March 2015.
  13. ^ Samsung reveals eight-core mobile processor on EEtimes
  14. ^ Now Producing Four Gigabit LPDDR3 Mobile DRAM, Using 20nm-class* Process Technology, Businesswire
  15. ^ Snapdragon 800 Series and 600 Processors Unveiled , Qualcomm
  16. ^ "JEDEC to Focus on Mobile Technology in Upcoming Conference". jedec.org. Retrieved 10 March 2015.
  17. ^ "Samsung Develops Industry's First 8Gb LPDDR4 Mobile DRAM". Samsung Tomorrow (Official Blog). Samsung Electronics. Archived from the original on 1 October 2014. Retrieved 10 March 2015.
  18. ^ http://www.softnology.biz/pdf/JESD79-4_DDR4_SDRAM.pdf JESD79 DDR4 SDRAM Standard
  19. ^ 'JEDEC Releases LPDDR4 Standard for Low Power Memory Devices', JEDEC Solid State Technology Association.
  20. ^ a b c JEDEC Standard: Low Power Double Data Rate 4 (LPDDR4) (PDF), JEDEC Solid State Technology Association, August 2014, retrieved 25 December 2014 Username and password "cypherpunks" will allow download.
  21. ^ "Row hammer refresh command". Patents. US20140059287. Retrieved 10 March 2015.
  22. ^ Reza, Ashiq (16 September 2016). "Memory Need" Gives Birth To "New Memory" (PDF). Qualcomm 3G LTE Summit. Hong Kong.
  23. ^ Shilov, Anton. "SK Hynix Announces 8 GB LPDDR4X-4266 DRAM Packages". Retrieved 28 July 2017.
  24. ^ "SK하이닉스 세계 최대 용량의 초저전력 모바일 D램 출시". Skhynix (in Korean). Archived from the original on 13 January 2019. Retrieved 28 July 2017.
  25. ^ "JEDEC Updates Standards for Low Power Memory Devices". JEDEC. Retrieved 28 July 2017.
  26. ^ a b c "JEDEC Updates Standard for Low Power Memory Devices: LPDDR5". jedec.org. Retrieved 19 February 2019.
  27. ^ Smith, Ryan (16 July 2018). "Samsung Announces First LPDDR5 DRAM Chip, Targets 6.4Gbps Data Rates & 30% Reduced Power". AnandTech.
  28. ^ "LPDDR5/5X 协议解读(三)WCK operation", Zhihu (in Chinese and English), 19 December 2022, retrieved 4 November 2023
  29. ^ Chang, Alex (Yeongkee) (October 2019), "Commands & New Features" (PDF), LPDDR5 Workshop, retrieved 4 November 2023
  30. ^ "JEDEC Publishes New and Updated Standards for Low Power Memory Devices Used in 5G and AI Applications". jedec.org. Retrieved 28 July 2021.
  31. ^ "Samsung Develops Industry's First LPDDR5X DRAM". Samsung.com. 9 November 2021. Retrieved 9 November 2021.
  32. ^ Frumusanu, Andrei (9 November 2021). "Samsung Announces First LPDDR5X at 8.5Gbps". Anandtech.com. Retrieved 9 November 2021.
  33. ^ "Micron and MediaTek First to Validate LPDDR5X". Micron Technology.
  34. ^ "SK hynix Develops World's Fastest Mobile DRAM LPDDR5T". 24 January 2023. Retrieved 12 June 2023.