Passive matrix addressing
Passive matrix addressing is an addressing scheme used in early LCDs. This is a matrix addressing scheme meaning that only m + n control signals are required to address an m × n display. A pixel in a passive matrix must maintain its state without active driving circuitry until it can be refreshed again.
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 n pixels on a row are 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-switched (lit) pixel corresponds to a Von, an off-switched (unlit) corresponds to a Voff potential.[1]
The potential across pixel at selected row i and column j is
and
for the unselected rows.[2]
This scheme has been expanded to define the limits of this type of addressing typical LCDs.[3][4]
Passive matrix addressed displays, such as ferroelectric liquid crystal displays, do not need the switch component of an active matrix display, because they have built-in bistability. Technology for electronic paper also has a form of bistability. Displays with bistable pixel elements are addressed with a passive matrix addressing scheme, whereas TFT LCD displays are addressed using active addressing.
See also
[edit]References
[edit]- ^ Wild, Peter J. "First-Hand Histories: Liquid Crystal Display Evolution - Swiss Contributions". Engineering and Technology History Wiki. ETHW. Retrieved June 30, 2017.
- ^ P. M. Alt, P. Pleshko Scanning limitations of liquid-crystal displays, IEEE Trans. Electron Devices, vol. ED-21, pp. 146–155, Feb. 1974.
- ^ J. Nehring, A. R. Kmetz: Ultimate limits for matrix addressing of RMS-responding liquid-crystal displays. IEEE Transactions on Electron Devices. Vol. 26, issue 5, pp. 795–802, May 1979.
- ^ T. N. Ruckmongathan, V. Arun, Babu Hemanth Kumar: Line-by-Line Addressing of RMS Responding Matrix Displays With Wavelets. Journal of Display Technology. Vol. 3, issue 4, pp. 413–420 December 2007.