HD404618 Datasheet, PDF (63/91 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404618 Series
Large Liquid-Crystal Panel Drive and V_LCD: To drive a large-capacity LCD, decrease the resistance of
the built-in division resistors by attaching external resistors in parallel, as shown in figure 38.
The size of these resistors cannot be simply calculated from the LCD load capacitance because the matrix
configuration of the LCD complicates the paths of charge/discharge currents flowing through the
capacitors. The resistance will also vary with lighting conditions. This size must be determined by trial
and error, taking into account the power dissipation of the device using the LCD, but a resistance of 1 to 10
kΩ would usually be suitable. (Another effective method is to attach capacitors of 0.1 to 0.3 µF.)
Always turn off the power switch (set bit 1 of the LCR to 0) before changing the liquid crystal drive
voltage (V_LCD).
V_CC (V₁ )
R
V₂
R
V₃
R
GND
V_CC
V_CC
V_CC
V_CC
V_CC ≥ V_LCD ≥ GND
C
C
C
V_CC (V₁ )
R
V₂
R
V₃
R
C = 0.1 to 0.3 µF
GND
V_LCD
V_LCD
V_LCD
V_LCD
V_{CC COM1}
V₁
V₂
V₃
GND
SEG1
to
SEG32
.
32
4-digit LCD
with sign
Static drive
V_CC
COM1
COM2
V₁
V₂
V₃
GND
SEG1
to
SEG32
2
.
32
8-digit LCD
1/2 duty cycle, 1/2 bias drive
V_CC
COM1
to
3
V₁ ^COM3
10-digit LCD
. with sign
V_{2 SEG1}
32
V₃
to
GND ^SEG32
1/3 duty cycle, 1/3 bias drive
V_CC
COM1
to
4
. ^{16-digit LCD}
V₁ ^COM4
V_{2 SEG1}
32
V₃
to
GND ^SEG32
1/4 duty cycle, 1/3 bias drive
Figure 38 LCD Connection Examples
61