HD66724 Datasheet, PDF (96/117 Pages) Hitachi Semiconductor – (Graphics LCD Controller/Driver with Key Scan Function)

HD66724/HD66725
Partial-Display-On Function
The HD66724/HD66725 can program the liquid crystal display drive duty ratio setting (NL2-0 bits), liquid
crystal display drive bias value selection (BS2-0 bits), boost output level selection (BT1/0 bit) and contrast
adjustment (CT4-0 bits). In the three-line display mode (1/26 duty ratio), the HD66724/HD66725 can
drive only one line in the center of the screen by combining these register functions and the centering
display (CEN bit) function. This is called partial-display-on. Lowering the liquid crystal display drive duty
ratio as required saves the liquid crystal display drive voltage, thus reducing internal current consumption.
This is suitable for calendar or time display, which needs to be continuous in the system standby state with
minimal current consumption. Here, the non-displayed lines are constantly driven by the deselection level
voltage, thus turning off the LCD for the lines.
In general, lowering the liquid crystal display drive duty ratio decreases the optimum liquid crystal display
drive voltage and liquid crystal display drive bias value.
Table 47 Partial-Display-On Function
Item
Character display
Segment display
Centering display
LCD drive duty ratio
LCD drive bias value (optimum)
LCD drive voltage
Frame frequency (fosc = 32 kHz)
Normal 3-Line Display
1st to 3rd lines displayed
Possible (144)
Not necessary (CEN = 0)
1/26 (NL2/1/0 = 011)
1/6 (BS2-0 = 001)
Adjustable using BT1/0 and
CT4-0
77 Hz
Partially-On Display
Only one line in the center of the
screen
Possible (144)
Possible (CEN = 1)
1/10 (NL2/1/0 = 001) possible
1/4 (BS2-0 = 101)
Adjustable using BT1/0 and CT4-0
80 kHz
96