Passive matrix addressing
|
|
sv:Passiv matrisadressering Passive matrix addressing is an addressing scheme used in earlier LCD displays, and is likely to be used in future LCD displays. This is a matrix addressing scheme meaning that only n + m control signals are required to address a n × m display. A pixel in a passive matrix must maintain its state without active driving circuitry until it can be refreshed again.
A new display technology uses a bi-stable pixel, which maintains its state indefinitely without the need for individual transistor elements at each pixel.
The signal is divided into a row or select signal and a column or video signal. The select voltage determines the row that is being addressed and all m pixels on a row is addressed simultaneously. When pixels on a row are being addressed, a Vsel potential is applied, and all other rows are unselected with a Vunsel potential. The video signal or column potential is then applied with a potential for each m columns individually. An on-lighted pixel corresponds to a Von, an off-switched corresponds to a Voff potential.
The potential across pixel at selected row i and column j is
- <math>V_{ij} = V_{sel} - V_{on|off}<math>
and
- <math>V_{ij} = V_{unsel} - V_{on|off}<math>
for the unselected rows. The figure below illustrates a 3×3-matrix display.
- sketch figure finished
Passive matrix addressed displays such as ferroelectric Liquid crystal displays (LCD), do not need the switch-component of an active matrix display because it has a built-in bistability. Technology for electronic papers also have a form of bistability. Displays with bistable pixel elements are addressed with passive matrix addressing scheme, where as TFT-LCD-displays are addressed using active addressing.
See also: active matrix addressing, pixel geometry, LCD