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display parameter eg. Duty ratio and Bias
http://forum.lcdinfo.com/viewtopic.php?f=9&t=2208		 Page 1 of 1
Author:  micemouse8 [ Mon Apr 23, 2007 11:24 ]
Post subject:  display parameter eg. Duty ratio and Bias
hi guys,

can u guys help me with the term of duty ratio and bias for display. Im very new to display world. I appreciate your help
Author:  sonic [ Wed Apr 16, 2008 8:03 ]
Post subject: 
Hi everybody!

I'm joining to micemouse's question - can somebody answer it, plz? :roll:

I have a CSTN LCD without built in controller and my task is to create LCD scanning mechanism straight from the lpc2106 uc (WITHOUT using LCD controller).

According to the LCD documentation:
Drive Method: 1/240 DUTY 1/17 BIAS
Explain, plz, what does it mean??

THNXS anyway :lol:
Author:  Henri [ Sat Apr 19, 2008 11:49 ]
Post subject: 
http://www.google.fi/search?q=lcd+duty+ratio+bias

http://www.atmel.com/dyn/resources/prod ... oc8009.pdf

"The Duty Cycle or Duty Ratio is a number used to describe how long time each
segment is activated during each frame. When each segment driver is only driving
one segment the Duty Ratio is “static”. If the drivers are driving more than one
segment each the Duty Ratio is given as 1/(segments driven by each LCD driver).
The number of segments driven by each LCD driver is equal to the number of
common terminals. The Duty Ratio is therefore depending on the number of common
terminals in a given LCD glass. Figure 2-3 illustrates the relation between the number
of back-planes and the Duty Ratio used when controlling the LCD.

The Drive Bias (or just Bias) is related to the number of voltage levels used when
driving the LCD. The Bias is defined as 1/(number of voltage levels-1). The more
segments driven by each driver(1) the higher number of voltage levels are required. As
per the definition of Duty Ratio, there is a direct relation between the Bias required
and the Duty Ratio used."


http://www.intelligentdisplay.com/custom.html

"When referring to an LCD, what is the definition of Duty Rate?
The Duty Rate, also known as multiplex rate, is the fraction of total frame time that each row of the LCD is addressed. For example a 64 row passive display has a duty rate of 1/64th.

When referring to an LCD what is the definition of Bias Ratio?
The Bias Ratio of an LCD is also known as the Voltage margin and is defined as the ratio of V on (voltage on pixels that are currently addressed to the ON-state) divided by V off (voltage on pixels that are not currently addressed)."
Author:  sonic [ Mon Apr 21, 2008 6:14 ]
Post subject: 
Thanks again, Henri :lol:

I'm all reading
Author:  sonic [ Mon Apr 21, 2008 6:48 ]
Post subject: 
Henri, I've another question, if U don't mind. :oops:

As I understood Duty and Bias ratios are only characteristics of LCD drivers, so I can't affect (control) them.
Is it correct??
Author:  Henri [ Tue Apr 22, 2008 19:45 ]
Post subject: 
Pretty much so.

So you just need to provide the panel the data with the timings specified in the timing diagrams and things should be ok.
But again have to say this same thing: check the datasheet for your panel if it says anything contradicting this and believe the datasheet more than just some generic talk you heard here ;) There are so many different displays out there that it's difficult to say anything 100% certain.
Author:  sonic [ Wed Apr 23, 2008 10:24 ]
Post subject: 
Thank you, I'll try to read the datasheet carefully. :)
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