HD66766R Datasheet, PDF (74/97 Pages) Hitachi Semiconductor – 132 x 176-dot Graphics LCD Controller/Driver for 65K Colors

HD66766R
Rev. 1.0-1 / September 2002
How to determine the power setting value
1. Determine LCD drive bias
Determine LCD drive bias first. LCD drive bias is theoretically (1/SQRT (display duty)) optimal;
however, the total drive voltage can be reduced by lowering bias ratio. Consider the display quality, the
drive voltage and the current consumption.
2. Determine VOUT voltage
Determine factor of Vc1 regulator and step-up factor so as to set output voltage, VOUT of step-up circuit
1 4.0 to 5.75V, setting input voltage Vci2 of step-up circuit 2 more than +0.5V. Since the entire electric
power for driving LCD is supplied from step-up circuit, subsequent voltage fall need to be considered.
3. Segment drive voltage calculation
Segment output drive voltage is calculated by the following expression.
Vseg =
2 x B _{x VTH}
(B-1)
B : LCD drive bias ratio
Vth: LCD threshold voltage
4. Common drive voltage calculation
Common output drive voltage is calculated by the following expression.
Vcom = ^Vseg x (B+1)
2
B : LCD drive bias ratio
5. Determine input voltage of step-up circuit 2
Determine input voltage of step-up circuit 2. This voltage is determined by dividing Vcom voltage by
step-up factor; lower factors are used for low current consumption. Vci2 voltage need to be less than
VOUT voltage (4.0 to 5.75 V)- 0.5V.
Example of register setting on power supply
Examples of register setting values on power supply are described below.
Example 1: 1/176 duty ratio, Vcc = VREFL = 3.0V, 1/13 bias
BS3-0 = H’8
BT2-0 = H’4
BT3 = H’1
DC2-0 = H’6
TBD
AP1-0 = H’1
VC2-0 = H’0
VR2-0 = H’0
CT6-0
: bias adjustment 1.4 times
: step-up circuit 1 2 times step-up circuit 2 5 times
: operate voltage inverting circuit
step-up circuit 1 frequency 32 clocks step-up circuit 2 frequency 128 clocks
: low fixed current in the amplifier
: Vci1 = 0.92 x Vcc = 2.75V
: VREFM = 1.1 x VREFL
: appropriate contrast setting values
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