V10 V90, Von Voff, Vth Vsat, Vsel Vnsel
There are a lot of confusions among V10, V90, Von, Voff, Vth, Vsat, Vsel, Vnsel. Please find the explanation as below.
V10 & V90 | Vsat & Vth: Saturation & Threshold Voltage
V10 is the voltage at 10% of the transmission level, it is also named as the saturation voltage (Vsat).
V90 is the voltage at 90% of the transmission level, it is also named as the threshold voltage (Vth).
The ratio V10/V90 is defined as sharpness or steepness. It reflects how many multiplex the LCD can be used.
From Fig. 1 we can see, if V10>V90, it is a positive display, while V90>V10 is a negative display.
Fig.1 V10 and V90
Von & Voff: Turn on / off Voltage
Von is the turn on voltage of the circuit.
Voff is the turn off voltage of the circuit.
The LCD display Von and Voff can be calculated as below.
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*B: Bias, N: Duty, V0: LCD driving voltage.
If Von/Voff is bigger than V10/V90, with the proper adjustment, better contrast >9:1 can be achieved. From Fig. 2, we can see STN LCD contrast is better than TN LCD as the sharpness of STN LCD is bigger or better.
Fig.2 TN and STN LCD Curve
Fig. 3 shows how to calculate the max multiplex a LCD can drive.
Fig.3 Contrast Adjustment
Vsel & Vnsel: Select / Non-select Voltage
Vsel: Select voltage. For a multiplex LCD, a pixel or a segment is selected to show (turn on).
Vnsel: Non-select voltage. For a multiplex LCD, a pixel or a segment is not selected to show (turn on).
In the ideal driving, the contrast for selected pixels should be very good while non-selected can’t be seen. But in reality, we have to optimize the circuit bias and select liquid crystal material and LCD mode carefully to prevent non-selected pixels to show. If non-selected pixels show, we call it ghosting. See Fig. 4.
Fig. 4 LCD Ghosting
In order to prevent LCD ghosting, it will be best to select better sharpness LCD or to make V10/V90 as big as possible. See Fig. 5.
Fig.5 Select and Non-select Voltage
Orient Display has different ways to prevent LCD ghosting, please consult our engineering team for more details.