DDR is the standard jot down of RAM used in all modern computers.
One of the significant improvements over the generations of DDR RAM has been in power efficiency.
While this doesnt sound like much, it can severely impact the battery life of battery-powered devices.
To help to extend battery lives, a low-power variant of DDR was standardized, LPDDR.
However, more significant changes exist, and the generations are not directly comparable.
Despite being standardized by the same group, JEDEC, the standards themselves are independently developed.
LPDDR is primarily used in low-powered devices such as mobile phones, tablets, and some laptops.
So LPDDR needs to offer capable performance as well as reduced power consumption.
One of the significant differences between DDR and LPDDR is that DDR uses a fixed 64-bit bus.
LPDDR also offers 32-bit or 16-bit bus options for use cases with lower requirements.
LPDDR1
LPDDR retroactively referred to as LPDDR1, didnt make massive changes from the DDR1 standard.
The main difference was the reduction in voltage from 2.5 to 1.8 volts.
Two I/O clock speeds were standardized, 200MHz and 266.7MHz in LPDDR1E.
This allowed for a data transfer rate of 400MTs or 533.3MTs with a prefetch size of 2n.
The 266.7MHz speed is actually faster than was ever standardized in DDR1.
This is primarily due to the improvements in microelectronics.
LPDDR2
Standardized in 2009, LPDDR2 ran at 1.2V or 1.8V in the LPDDR2E version.
It ran at double the I/O clock speed of LPDDR1 with 400MHz or 533.3MHz.
These stats bring it in line with the fastest two standard DDR2 speeds.
LPDDR2 mainly adds additional partial refresh options outside of the voltage reduction.
LPDDR3
In 2012 JEDEC standardized LPDDR3.
LPDDR4
DDR4 and LPDDR4 were both standardized in 2014.
LPDDR5
In 2019 LPDDR5 was standardized a year before the DDR5 standard.
It keeps the same prefetch size as LPDDR4 of 16n but doubles the transfer rate to 6400Mts.
LPDDR5X memory is expected to first appear in mobile products in 2023.
Conclusions
LPDDR is a series of memory standards for RAM designed for use in power-constrained environments.
It can often be found in smartphones, tablets, and some laptops.
These changes were inverted with the DDR5 and LPDDR5 standards.
However, it is unclear how much this portion of the LPDDR standard is used.
LPDDR standards are generally being developed faster than DDR standards.
This process was caused because LPDDR started development later.
However, it has now advanced beyond the DDR5 standard.
It is unclear but unlikely that it can maintain this development pace.
