Nonvolatile Logic Memory with Zero Standby Power Consumption

Kyoto, Japan – Semiconductor manufacturer ROHM Co., Ltd, announces the development of the first IC chip integrating nonvolatile logic circuitry in the internal data storage area (register). FeRAM (Ferroelectric Random Access Memory), a type of memory capable of retaining the state of the chip’s internal operations even when no power is supplied, was created using ferroelectric element technology.

Logic ICs such as CPUs, have computational state retention circuits known as registers which temporarily store information on the progress and results of various processing operations and retain and modify the operating state of the IC and peripheral devices. Information held in existing IC registers is erased when power is cut (referred to as volatility), making current flow imperative in order to maintain storage.

Although previous attempts to make IC registers nonvolatile using ferroelectric elements have been made, no viable products exist due to problems such as increased load capacitance in the IC logic circuit along with greater power load and signal delays. ROHM’s new ferroelectric separate structure, combined with original technology that allows the register area to be made nonvolatile without harming the logic performance or reliability of the IC, solves these problems simultaneously.

Actual tests conducted on this nonvolatile logic technology, which reduces standby power consumption to zero, has effectively decreased CPU power consumption by approximately 70%. Implementing modifications such as placing blocks not performing Write/Read operations into sleep mode even during CPU operation, can reduce power consumption by an additional 15% to an estimated 85% or more, with further optimization of the power supply (i.e. closely managing ON/OFF operation at the register/computation circuit level within each block) enabling a power efficiency exceeding 95%.

Practical applications include significantly reducing the startup time of PCs which currently number in the several tens of seconds to that of TVs. In addition, many home appliances are constantly supplied with electricity and continue to consume power (standby power consumption) even when turned OFF in order to retain internal data. This amounts to as much as 15 billion kWh wasted each year in Japan alone [estimate based on “Standby Power Consumption Survey Report” (The Energy Conservation Center, Japan)]. Integrating nonvolatile logic technology in the logic ICs used in these electronic products can result in tremendous energy savings for entire markets.

ROHM will be making proposals to its customers regarding the use of nonvolatile custom logic ICs and has scheduled mass production to begin after one year.

•Glossary

• Register
  A memory area in digital processor (logic) circuits that temporarily stores and maintains operation data and conditions during microcontroller processing.
• Volatile/Non-volatile Memory
  Volatile memory is memory that requires power to maintain the stored information, as opposed to non-volatile memory that does not require a constant power supply.
• Load Capacity
  The primary determinant of current (power) consumption, due to the normally slow voltage change within electronic circuits.

■Photo 1. CPU Prototype Utilizing Nonvolatile Logic Technology (Nonvolatile CPU)	■Photo 1. Nonvolatile CPU Chip

■Figure 1. Example of Nonvolatile CPU Operation
■Figure 2. Basic CPU Processing Blocks	■Figure 3. Examples of Power Control Using Nonvolatile Logic Technology