13.3.7
Boosting the LCD Drive Power Supply
When a large panel is driven, the on-chip power supply capacity may be insufficient. In this case,
the power supply impedance must be reduced. This can be done by connecting bypass capacitors
of around 0.1 to 0.3 µF to pins V1 to V3, as shown in figure 13-17, or by adding a split-resistance
externally.
V0
V1
VCC
R = several kΩ to
several MΩ
R
H8/3887 Series
V2
V3
R
R
C= 0.1 to 0.3µF
VSS
Figure 13-17 Connection of External Split-Resistance
Connection to HD66100
13.3.8
If the segments are to be expanded externally, an HD66100 should be connected. Connecting one
HD66100 provides 80-segment expansion. When carrying out external expansion, select the
external expansion signal function of pins SEG40 to SEG37 with the SGX bit in LPCR, and set bits
SGS3 to SGS0 to 0000. Data is output externally from SEG1 of the LCD RAM. SEG36 to SEG1
function as ports.
Figure 13-18 shows examples of connection to an HD66100. The output level is determined by a
combination of the data and the M pin output, but these combinations differ from those in the
HD66100. Table 13-3 shows the output levels of the LCD drive power supply, and figures 13-11
and 13-12 show the common and segment waveforms for each duty cycle.
When ACT is cleared to 0, operation stops with CL2 = 0, CL1 = 0, M = 0, and DO at the data value
(1 or 0) being output at that instant. In standby mode, the expansion pins go to the high-
impedance (floating) state.
369
ETC [ ETC ]
