hd66100 Renesas Electronics Corporation., hd66100 Datasheet - Page 365

• Manufacturer Part Number: hd66100
• Description: H8/3867 Series
• Manufacturer: Renesas Electronics Corporation.

13.3.4
The H8/3867 Series has an on-chip step-up constant-voltage (5 V) power supply which enables a 5
V constant voltage to be obtained independently of V
H8/3827 Series.
When the SUPS bit is set to 1 in LCD control register 2 (LCR2), the step-up constant-voltage (5
V) power supply operates, and a 5 V constant voltage is output from the V
V
Note: The step-up constant-voltage (5 V) power supply must not be used for any purpose other
13.3.5
The use of the built-in split-resistance is normally the easiest method for implementing the LCD
power supply circuit, but since the built-in resistance is fixed, a certain direct current flows
constantly from the built-in resistance’s V
current dissipation of the LCD panel, if an LCD panel with a small current dissipation is used, a
wasteful amount of power will be consumed. The H8/3864 Series is equipped with a function to
minimize this waste of power. Use of this function makes it possible to achieve the optimum
power supply circuit for the LCD panel’s current dissipation.
1. Principles
350
0
and V
a. Capacitors are connected as external circuits to LCD power supply pins V1, V2, and V3, as
b. The capacitors connected to V1, V2, and V3 are repeatedly charged and discharged in the
c. At this time, the charged potential is a potential corresponding to the V1, V2, and V3 pins,
d. Power is supplied to the LCD panel by means of the charges accumulated in these
e. The capacitances and charging/discharging periods of these capacitors are therefore
f. The charging and discharging periods can be selected by software.
shown in figure 13.14.
cycle shown in figure 13.14, maintaining the potentials.
respectively. (For example, with 1/3 bias drive, the charge for V2 is 2/3 that of V1, and that
for V3 is 1/3 that of V1.)
capacitors.
determined by the current dissipation of the LCD panel.
than the H8/3864 Series’ LCD drive power supply. When a large panel is driven, the
power supply capacity may be insufficient. In this case, either use V
supply or use an external power supply circuit.
1
Step-Up Constant-Voltage (5 V) Power Supply
Low-Power-Consumption LCD Drive System
pins or connect a resistance to divide the voltage.
CC
to V
SS
. As this current does not depend on the
CC
. This feature is not provided in the
0
pin. Either short the
CC
as the power