Patent Application
20050083455
Embodiments of the present invention relate to memory systems that are integrated with LCD displays.
Battery-powered processing devices are subject to several different competing design criteria. For example, increasing the processing power of a computer's central processing unit or the amount of RAM memory provided thereon generally causes a corresponding increase in the rate at which the computer consumes power. Engineers are constantly challenged to design devices that provide increased processing power and increased storage capacity while, at the same time, prolonging battery life and decreasing the physical dimensions of those devices. Engineers are most acutely aware of these design constraints when designing processing systems for mobile applications, such as notebook computers, portable digital assistants, mobile phones, global positioning system (“GPS”) devices, automotive systems and other battery-powered devices.
Substantial research and development is underway in the area of polymer memories. Polymer memories are unlike traditional silicon-based RAM devices because, as their name implies, they are manufactured from polymers. Individual memory cells include a polymer material having a dipole moment. The orientation of the dipole moment may be controlled selectively to represent stored data. Polymer memories can be advantageous for battery-powered devices because stored data remains valid even when power is removed from the memory system.
The inventors have investigated polymer memories for battery-powered processing devices and have identified a need in the art for such a processing device that integrate polymer memories therein without increasing the form factor of the device.
According to embodiments of the present invention, greater integration may be achieved between a polymer memory system and a display system. Conventionally, LCD displays and the like define a number of liquid crystal chambers that include transmissive and non-transmissive regions. Polymer memory cells may be disposed within the chambers co-located with the non-transmissive regions thereof. Thus, the memory cells provide only limited interference with the image-bearing functions of the display (if they interfere at all) but provide an extra dimension of functionality to the display.
Conventionally, LCD displays 100 include a variety of polarizing filters and other optical elements that contribute to the displays' ability to carry image information. Such structures may be used cooperatively with the various embodiments of the present invention; they are omitted from the illustration of
Embodiments of the present invention introduce a polymer memory system into a chamber 130 of a display 100. Polymer memory cells PM1, PM2, PM3 may be disposed in one or more non-transmissive regions 170 of the display 100. Three such cells are shown in the illustrated embodiment but the number may be tailored to suit individual implementation needs. Because the polymer memory cells PM1, PM2, PM3 appear in a non-transmissive area of the display, they should provide limited interference, if any, to the optical performance of the display 100.
The display 100 may include control lines 190, 200 to provide electrical connectivity between the polymer memory cells PM1, PM2, PM3 and devices external to the display 100 (not shown). As indicated, the conductivity of a polymer memory cell may be controlled to represent digital data. Thus, when a predetermined potential is applied to a ‘supply line’ on a first portion of the polymer memory cell, the presence or absence of a current on a ‘return line’ on a second portion of the cell may indicate a state of stored data. In an embodiment having a predetermined number N of the cells in a chamber, there may be N supply conductors 190 (not shown individually) and a single return conductor 200 or there may be a single supply conductor 190 and a N return conductors 200 (again, not shown individually) to permit individual addressing of the polymer memory cells within the chamber 150. Other embodiments permit the supply and return conductors 190, 200 to be aligned with but insulated from addressing conductors 210, 220 that drive the transistor 140 and LCD materials, to minimize the profile of all the conductors 190, 200, 210 and 220 with reference to light propagating through the display 100.
The display structure 100 of
In many applications, it can be expected that there will be no electrical interference between electrical components of the display's optical elements (e.g., the TFTs 140 and addressing conductors 200, 210 and the polymer memory system provided therein. Particularly where the TFT transistors 140 are fairly large and the driving potentials for the LCD materials are fairly low, operation of these elements should not interfere with reading and writing operations of the memory system. Accordingly, memory addressing operations and pixel addressing operations can be performed without regard for one another.
According to other embodiments of the present invention, however, it may be desired to stagger memory addressing operations in time with respect to addressing operations for co-located TFTs 140 to ensure noise immunity. In an active matrix display, each pixel is addressed individually by its own set of addressing wires. Thus, image information for a pixel at coordinates [0,0] (
Typically, the time required to write data to a transistor in an LCD display is a very small percentage of the display's refresh time. In a display that refreshes image information at least 60 times per second (a frame period of 16.7 ms), it may require only 10-20 ns to write data to a single TFT or a row of TFTs. Such data transfer times will only decrease as pixel driving technologies improve. Thus, a large percentage of the operational time of the display remains available for memory accesses.
The capacity of a polymer memory system 400 may be increased by providing a plurality of layers of memory cells 410 in the polymer memory system 400. Accordingly, in an embodiment, the memory system 400 may include a plurality of layers (only two are shown in
The layers need not be provided identically to one another. For example, rather than stack individual cells 410 directly on top of one another, a cell in one layer may be placed in a location that is occupied by a space between cells in another layer. Further, a driving conductor 420 from one layer need not run parallel to driving conductors 420 from other layers. Similarly, data lines 430 from one layer need not run parallel to data lines 430 from another layer. Additionally, rather than providing a driving conductor 420 from one layer adjacent to data lines 430 of another layer, it may be beneficial to provide driving conductors 420 from each layer in an adjacent relationship or data lines 430 from each layer in an adjacent relationship. Such embodiments are within the spirit and scope of the present invention.
The polymer memory systems of the foregoing embodiments may be provided as general purpose random access memory (“RAM”) for storage of any kind of data to be used by a processor-based system 500. As is known, polymer memories are non-volatile; stored data remains valid in the memory even after power is removed. Thus, polymer memories are expected to find ready application in a variety of battery-powered processor-based systems 500, such as laptop/notebook computers, personal digital assistants, mobile phones and the like. By storing application data in a polymer memory, one may avoid many power-intensive operations such as loading an operating system on device start-up from a mechanical storage device such as a magnetic or optical disc. The present invention permits a large scale memory system to be integrated into a display to be used in such systems with almost no increase in the physical dimensions of the display.
Additionally, depending on the physical dimensions of the display system being used, the polymer memory system of the foregoing embodiments have the capability to replace certain bulk storage devices currently being used in computer systems, such as magnetic or optical disk drives. Generally, designers of a great many components in computer systems face constant pressure to reduce the physical size of such components. This design pressure, however, is not always applied to displays. For example, a variety of laptop/notebook computers are currently are marketed with display dimensions of 14 to 15 inches across the diagonal. Thus, by integrating the polymer memory system with the spatial area available for most LCD displays, one may create a memory system with relatively large capacity.
While the polymer memory system may store data that is used by the LCD display (for example, graphics data), this need not be the case. As noted above, the polymer memory system may be used for storage of any data that may be stored by other conventional RAM circuits.
Several embodiments of the present invention are specifically illustrated and described herein. However, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.
