hd66740 Renesas Electronics Corporation., hd66740 Datasheet - Page 52

• Manufacturer Part Number: hd66740
• Description: 112 X 80-dot Graphics Lcd Controller/driver - Hitachi Semiconductor
• Manufacturer: Renesas Electronics Corporation.

HD66740
Contrast Adjuster
Software can adjust 64-step contrast for an LCD by varying the liquid-crystal drive voltage (potential
difference between V
function). The value of a variable resistor between V
x R unit within a range from 0.05 x R through 3.20 x R, where R is a reference resistance obtained by
dividing the total resistance.
The HD66740 incorporates a voltage-follower operational amplifier for each of V1 to V5 to reduce
current flowing through the internal bleeder resistors, which generate different liquid-crystal drive
voltages. Thus, CT5-0 bits must be adjusted so that the potential differences between V
between V5 and GND are 0.4 V or higher when liquid-crystal drives, particularly when the VR is
small.
LCD
and V1) through the CT bits of the contrast adjustment register (electron volume
Figure 27
VLCD
GND
VR
R0
R
R
R
R
Contrast Adjuster
HD66740
52
LCD
+
+
+
+
+
-
-
-
-
-
and V1 (VR) can be precisely adjusted in a 0.05
CT
V1
V2
V3
V4
V5
GND
LCD
and V1 and